amazing ARB pricing

[John Larkin]

https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch

Other places have this box for $99.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

[Clifford Heath]

On 26/10/18 8:27 am, John Larkin wrote:
> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>
> Other places have this box for $99.

Or less. Many clone suppliers of this design.
The DDS is probably a AD9851. Frequency counter
modules are available for < $15 (cloned hobbyist
design, perhaps incorporated here?) 2.4" TFT
color LCD screens retail under $5 in singles,
and there's plenty of driver code for Arduino
and STM32. Don't know what DAC the ARB generator
uses, but there's not much magic there.

The magic is to be able to make a profit, at
these prices.

<https://www.aliexpress.com/item/JDS6600-Series-MAX-60MHz-DDS-Function-Signal-Source-Digital-Control-Dual-Channel-Arbitrary-Wave-Function-Generator/32866324994.html>

[George Herold]

I have no idea about this, but we've bought some semi broken stuff
on amazon. So check it out when it comes in.

George H.

[Frank Miles]

On Thu, 25 Oct 2018 14:27:15 -0700, John Larkin wrote:

> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/
dp/B07BF7Y7TJ/ref=sr_1_3?
ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%

252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>
> Other places have this box for $99.

Interesting, but when I looked it sez: "currently unavailable".

[John Larkin]

There are a zillion rebrands of that same box.

It's amazing that someone cound set up a serious electronics lab now
(scope, generators, DVM, power supplies, soldering stuff, Spice and
PCB software) for way under $1000, and get parts and proto PC boards
dirt cheap. A web site for advertising could be free. All you'd need
then is ideas and energy.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Jasen Betts]

On 2018-10-26, John Larkin <jjla...@highlandtechnology.com> wrote:
> On Fri, 26 Oct 2018 02:47:43 -0000 (UTC), Frank Miles
><f...@u.washington.edu> wrote:
>
>>On Thu, 25 Oct 2018 14:27:15 -0700, John Larkin wrote:
>>
>>> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/
>>dp/B07BF7Y7TJ/ref=sr_1_3?
>>ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%
>>252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>>>
>>> Other places have this box for $99.
>>
>>Interesting, but when I looked it sez: "currently unavailable".
>
> There are a zillion rebrands of that same box.

For us who were late to the game what was the "amazing" price?
currently the pricing can only be described as disappointing.

--
When I tried casting out nines I made a hash of it.

[bitrex]

It's part of why I'm driving a 40k car and have my own little home to
live in at this point in my life instead of waiting tables with an art
school degree. I still make art but a boy's gotta eat

[speff]

On Thursday, 25 October 2018 17:27:24 UTC-4, John Larkin wrote:
> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>
> Other places have this box for $99.

$99 would be a very good price, from what I can see, better than China list- looks like a more normal price would be about $150-$200 in the US for the 60MHz version. The lower frequency versions are significantly cheaper.

It appears to use an Altera Cyclone IV FPGA driving 14-bit DAC. 320x240 color TFT. This is NOT your hobbyist DDS chip.

Certainly not as nice as a Keysight (or whatever they're calling themselves these days) or a Rigol, but very economical.

--sp

[speff]

P.S. the manufacturer appears to victim of being badmouthed by some of their competitors using fake names.

So they say "‘True gold fears no fire" (a person of integrity can withstand a severe test)

https://chinese.yabla.com/chinese-english-pinyin-dictionary.php?define=%E7%9C%9F%E9%87%91%E4%B8%8D%E6%80%95%E7%81%AB%E7%82%BC

Looks like there might be competitive units (possibly copies) which use resistor networks direct from the FPGA outputs rather than the DAC. They also claim 60s short-circuit capability on the outputs (my Agilent Arb has a bunch of relatively expensive op-amps in parallel to get the output drive). I would say some caution is called for if one wants to buy one of these apparently identical units.


--sp

[Clifford Heath]

On 26/10/18 7:42 pm, speff wrote:
> On Thursday, 25 October 2018 17:27:24 UTC-4, John Larkin wrote:
>> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>>
>> Other places have this box for $99.
>
> $99 would be a very good price, from what I can see, better than China list- looks like a more normal price would be about $150-$200 in the US for the 60MHz version. The lower frequency versions are significantly cheaper.
>
> It appears to use an Altera Cyclone IV FPGA driving 14-bit DAC. 320x240 color TFT. This is NOT your hobbyist DDS chip.

The prevalence of cloning in this kind of device
is usually because someone published the designs.

It's often an advanced hobbyist. I have a couple
of gadgets like this; if you search hard enough
you can find the original blog postings showing
where the design was developed. There are plenty
of hobbyists advanced enough to have developed
this design.

I haven't searched, but mere hardware copying
wouldn't result in the plethora of clones; the
original software has to be published somewhere.
Otherwise the cloners would have to write it again
(differently) to accommodate any design changes,
and that's too much like hard work; they'd need to
understand how what they were cloning works.

[speff]

Googled it and there's a huge thread at EEVBLOG on this
product.

https://www.eevblog.com/forum/testgear/feeltech-fy6600-60mhz-2-ch-vco-function-arbitrary-waveform-signal-generator/


-sp

[John Larkin]

On Fri, 26 Oct 2018 01:42:11 -0700 (PDT), speff <spe...@gmail.com>
wrote:

I have a classic B+K analog (well, with frequency counter) fungen on
my bench. The human interface is highly advanced: you turn knobs to do
stuff. I wish my car did that.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Clifford Heath]

Good info, thanks. My comments about cloners stand, I think.

[Carl]

I didn't read the whole thread, just the first and last few plus a page here
and there, but by the end the take home message seemed to be to get the
model 6800 since it fixes most or all of the complaints, especially about
grounding. It's on eBay for $110-120 depending on frequency range (20, 30,
40, 60 MHz) so basically the same price. Interestingly, each frequency step
only adds about $2-3 to the price so I don't see why anyone wouldn't just
get the 60 MHz model.

--
Regards,
Carl Ijames

[Klaus Kragelund]

I didn’t read the entire thread, but there was a discussion about jitter and high frequency shape distortion

But good link, Larkin, I have a HP33120A arb generator

It’s really good. I bought it 20 years ago, and I measured most important specs a couple of months ago, and almost no drift

Amazingly bad design about square wave function, not possible to generate duty cycle above 80 or below 20 percent. Need to fiddle with burst mode

Also, no signal off button

So will buy the Chinese model for sure, even though I do not need it badly or even remotely (wife buys shoes, I buy tools and electronics)

Cheers

Klaus

[Klaus Kragelund]

A 200MHz scope for 379 USD:

https://www.amazon.com/Siglent-Technologies-SDS1202X-Oscilloscope-Channels/dp/B06XZML6RD/ref=pd_aw_sbs_328_of_13?_encoding=UTF8&pd_rd_i=B06XZML6RD&pd_rd_r=0578ee0f-d95c-11e8-8a27-e7c97784a407&pd_rd_w=dV3r6&pd_rd_wg=B2YIF&pf_rd_i=mobile-dp-sims&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=926ebe02-3236-40c6-ac63-01ad178f498a&pf_rd_r=Y2SMMGCRT1ZGCYBYF1GE&pf_rd_s=mobile-dp-sims&pf_rd_t=40701&psc=1&refRID=7M8XSZS3XF3JSQZ68R27

Cheers

Klaus

[speff]

China domestic retail pricing is almost exactly double for the 60MHz compared to 20MHz. That's for the original unit from the factory. Some (maybe most) of the eBay ones appear to be clones. I wonder if they cheaped out on the DAC.

--sp

[tabb...@gmail.com]

On Friday, 26 October 2018 23:26:30 UTC+1, speff wrote:
> On Friday, 26 October 2018 14:05:08 UTC-4, Carl wrote:

> > grounding. It's on eBay for $110-120 depending on frequency range (20, 30,
> > 40, 60 MHz) so basically the same price. Interestingly, each frequency step
> > only adds about $2-3 to the price so I don't see why anyone wouldn't just
> > get the 60 MHz model.

> China domestic retail pricing is almost exactly double for the 60MHz compared to 20MHz. That's for the original unit from the factory. Some (maybe most) of the eBay ones appear to be clones. I wonder if they cheaped out on the DAC.

you don't think they cheaped out on every bit?


NT

[John Larkin]

On Thu, 25 Oct 2018 14:27:15 -0700, John Larkin

<jjlarkin@highland_snip_technology.com> wrote:

>
>
>https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>
>Other places have this box for $99.

This one is $61, shipped.

https://www.amazon.com/KKmoon-Precision-Dual-channel-Generator-Arbitrary/dp/B014KT3IT6/ref=pd_lutyp_crtyp_simh_3_6?_encoding=UTF8&pd_rd_i=B014KT3IT6&pd_rd_r=9d22d9de-62d5-48ea-92f3-b42f43bcbd69&pd_rd_w=ZXu2r&pd_rd_wg=yOKdh&pf_rd_i=desktop-typ-carousels&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=6a44b7cf-39a3-4c0a-8513-6ba7e2be5761&pf_rd_r=28CNWJQARWQG5BTFSAE6&pf_rd_s=desktop-typ-carousels&pf_rd_t=40701&psc=1&refRID=28CNWJQARWQG5BTFSAE6

The specs are interesting.

[George Herold]

I'm totally in love with this keysight 'scope, but I think it's
close to ~$1k.. it just does everything right.
(and it all starts with the triggering.)

I turn it on and it remembers all the last settings,
all stuff should do that.

George H.

[Johnny B Good]

On Fri, 26 Oct 2018 13:27:07 -0700, Klaus Kragelund wrote:

> A 200MHz scope for 379 USD:
>

I've been considering replacing my ancient 1950s CRT dual beam 70Lbs
'scope with something more up to date recently and this Siglent
Technologies SDS1202X-E 'scope looked like it might be a good value
proposition (a snip at a mere £363.05 for UK customers via Amazon's
'Fulfilment' delivery) so have checked out some reviews[1] which seem to
confirm this view.

However, this is a subject of very recent interest so I haven't yet
researched this in any great depth as yet so I was wondering if you had
any advice on this 'scope or possibly better alternatives (100MHz B/W
dual trace at a minimum) that you could offer to aid me in my search for
a reasonably specced and priced unit?

[1] Amazon customer reviews here:

<https://www.amazon.co.uk/Siglent-Technologies-SDS1202X-
Oscilloscope-Channels/dp/B06XZML6RD/ref=sr_1_1?
ie=UTF8&qid=1540608976&sr=8-1&keywords=sds1202x-e>

TinyURL <https://tinyurl.com/ydgpong6>

(click the customer reviews link near the top of the page)


The Defpom's Repair Channel review videos here:

<https://youtu.be/64kxGDOg7es?t=19> Part 1
<https://youtu.be/laK1v2Zas4o?t=12> Part 2

--
Johnny B Good

[speff]

The original manufacturer, probably not. They say they've sold more than 100K pieces.

------
Listen to the advice of the majority of users, and strive to provide customers with friends with more convenient and easy to use high-performance, cost-effective products.

Product upgrade!

1. Add AM, FM, PM, ASK, FSK, PSK modulation functions!

2. The phase adjustment resolution is upgraded to 0.01°;

3. The duty cycle adjustment resolution is upgraded to 0.01%;


4. The square wave rising edge and falling edge time are adjustable. When the instrument sets the square wave output, press the F4 button to switch between the duty cycle and the lifting edge time setting, thus making the instrument more applicable!

5, the use of silicone buttons and gold-plated button contacts, so that the instrument button life is longer, the operating feel is more comfortable.

[Tom Gardner]

On 27/10/18 04:32, Johnny B Good wrote:
> On Fri, 26 Oct 2018 13:27:07 -0700, Klaus Kragelund wrote:
>
>> A 200MHz scope for 379 USD:
>>
>
> I've been considering replacing my ancient 1950s CRT dual beam 70Lbs
> 'scope with something more up to date recently and this Siglent
> Technologies SDS1202X-E 'scope looked like it might be a good value
> proposition (a snip at a mere £363.05 for UK customers via Amazon's
> 'Fulfilment' delivery) so have checked out some reviews[1] which seem to
> confirm this view.
>
> However, this is a subject of very recent interest so I haven't yet
> researched this in any great depth as yet so I was wondering if you had
> any advice on this 'scope or possibly better alternatives (100MHz B/W
> dual trace at a minimum) that you could offer to aid me in my search for
> a reasonably specced and priced unit?

This topic comes up once per week on EEVBlog forum, and is discussed
ad nauseam there. Many of the responses are "just buy X it is
the best available now", but a few are more measured.

There are also some long /long/ threads on reviews of the popular
bottom-end scopes.

Read EEVBlog forum and you will have a better idea of what
questions you should ask, and some answers for them.

Don't throw the boat anchor away until you are satisfied
that the new scope can do everything you want at least as
well as the boat anchor.

[speff]

My Tek battery powered digital scope lies to you if you set the
sweep too slow for the signals.. there does not appear to be any
anti-aliasing filter. Analog scopes don't lie in that particular
disturbing manner.

--sp

[Martin Riddle]

On Fri, 26 Oct 2018 17:57:14 -0700, John Larkin

<jjlarkin@highland_snip_technology.com> wrote:

>On Thu, 25 Oct 2018 14:27:15 -0700, John Larkin
><jjlarkin@highland_snip_technology.com> wrote:
>
>>
>>
>>https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>>
>>Other places have this box for $99.
>
>
>This one is $61, shipped.
>
>https://www.amazon.com/KKmoon-Precision-Dual-channel-Generator-Arbitrary/dp/B014KT3IT6/ref=pd_lutyp_crtyp_simh_3_6?_encoding=UTF8&pd_rd_i=B014KT3IT6&pd_rd_r=9d22d9de-62d5-48ea-92f3-b42f43bcbd69&pd_rd_w=ZXu2r&pd_rd_wg=yOKdh&pf_rd_i=desktop-typ-carousels&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=6a44b7cf-39a3-4c0a-8513-6ba7e2be5761&pf_rd_r=28CNWJQARWQG5BTFSAE6&pf_rd_s=desktop-typ-carousels&pf_rd_t=40701&psc=1&refRID=28CNWJQARWQG5BTFSAE6
>
>The specs are interesting.

I splurged....

<https://www.amazon.com/GW-Instek-MFG-2160MR-Multi-Channel-Modulation/dp/B072PXK6ZB>

Cheers

[Tom Del Rosso]

John Larkin wrote:
> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>
> Other places have this box for $99.

Just how arbitrary is an ARB? Can any of them download a waveform from
a scope and make little adjustments like reducing overshoot or ringing,
so you can see if doing so would help before you go to the effort of
reducing it for real?

Or do they just do complex modulations, or is it just another name for
function generator?

[speff]

I don't think you'll be disappointed. I have this one:

https://www.rigolna.com/products/waveform-generators/dg4062/

[jjhu...@gmail.com]

To each their own. When I wanted something a bit more portable than my Tek 7903 I got a used tek for ~$250 USD, spent some time cleaning it up and calibrating. Good as new. Not quite as glitzy but solid and serviceable.

Some tek scopes have Tek specific ICs and modules that are very hard to find, but on the whole, very serviceable, if that be your inclination.
Post your interest on the tek NG and you will receive some very useful info.
J

[John Larkin]

On Sat, 27 Oct 2018 14:11:31 -0400, "Tom Del Rosso"
<fizzbin...@that-google-mail-domain.com> wrote:

>John Larkin wrote:
>> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>>
>> Other places have this box for $99.
>
>Just how arbitrary is an ARB? Can any of them download a waveform from
>a scope and make little adjustments like reducing overshoot or ringing,
>so you can see if doing so would help before you go to the effort of
>reducing it for real?

It sure looks like you can load waveforms. You could slurp a wavaform
from a scope, math it, and then load the ARB.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Joerg]

On 2018-10-25 14:27, John Larkin wrote:
>
>
> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>
> Other places have this box for $99.
>
>

I have a no-name ARB because I needed one year ago for aerospace
testing. The 1st one had a bum FPGA. Was replaced. The 2nd one now has a
slowly failing rotary encoder. Oh well.

--
Regards, Joerg

http://www.analogconsultants.com/

[Carl]

Tom Del Rosso wrote:
>Just how arbitrary is an ARB? Can any of them download a waveform from a
>scope and make little adjustments like reducing overshoot or ringing, so
>you can see if doing so would help before you go to the effort of reducing
>it for real?
>
>Or do they just do complex modulations, or is it just another name for
>function generator?

Some may be able to download directly from a scope but it would probably
have to be the same brand. They usually have front panel waveform creation
and editing where you can step through a waveform point by point and either
directly enter a numerical value or use the up and down arrows to modify it.
All should be able to talk to a PC, and the scope should also be able to
talk to the PC so you should be able to upload a waveform with the scope
software, either save it directly or export as a CSV file depending on the
brands, then import into the ARB software, edit as desired, and then
download. The waveform is point-by-point completely arbitrary but then you
have to take into account the sample rate and bandwidth of the ARB to
determine just how sharp a corner you can actually get and also what the
actual output frequencies will be (if the scope and ARB sampling rates
differ, for example). They are great fun to play with, and actually useful
too :-). One gotcha for me with the cheap ARBs in this thread is that the
longest a single waveform can be is only 8192 points. I assume that you can
slow down the sample rate to extend that in time but eventually you hit the
minimum required bandwidth. They can store 64 waveforms and might be able
to chain waveforms together with no glitches or timing issues which would
allow one 512 Kpt waveform but you would have to handle the breaking apart
and downloading in software. I haven't read the manual to see if all that
would work.

--
Regards,
Carl Ijames

[Johnny B Good]

On Sat, 27 Oct 2018 09:36:54 +0100, Tom Gardner wrote:

> On 27/10/18 04:32, Johnny B Good wrote:
>> On Fri, 26 Oct 2018 13:27:07 -0700, Klaus Kragelund wrote:
>>
>>> A 200MHz scope for 379 USD:
>>>
>>>
>> I've been considering replacing my ancient 1950s CRT dual beam 70Lbs
>> 'scope with something more up to date recently and this Siglent
>> Technologies SDS1202X-E 'scope looked like it might be a good value
>> proposition (a snip at a mere £363.05 for UK customers via Amazon's
>> 'Fulfilment' delivery) so have checked out some reviews[1] which seem
>> to confirm this view.
>>
>> However, this is a subject of very recent interest so I haven't yet
>> researched this in any great depth as yet so I was wondering if you had
>> any advice on this 'scope or possibly better alternatives (100MHz B/W
>> dual trace at a minimum) that you could offer to aid me in my search
>> for a reasonably specced and priced unit?
>
> This topic comes up once per week on EEVBlog forum, and is discussed ad
> nauseam there. Many of the responses are "just buy X it is the best
> available now", but a few are more measured.

I've looked at few of those reviews now and I'm more than mindful of
their very short BB dates for such rapidly evolving kit. Apropos of
which, the Rigol DS1052E, a ten year old design which I referred to in
note [2] at the end of this post, which is still being sold by Rigol uk
at just a hundred quid less than the asking price for an SDS1202X-E.

>
> There are also some long /long/ threads on reviews of the popular
> bottom-end scopes.

I haven't explored any of those threads (assuming you're referring to
the comments below the youtube vids) in any depth so far.

>
> Read EEVBlog forum and you will have a better idea of what questions you
> should ask, and some answers for them.

Thanks for the suggestion. I'll google my way to that forum now that
I've read the wikipedia article on oscilloscopes by way of a refresher/
technology update course.

Mind you, I have to say that the Siglent Technologies SDS1202X-E is
still looking like the "Best Bang for my Buck" option right now despite
it still being quite a chunk of cash to part with in one go. There are
plenty of alternatives at modestly cheaper price points but they seem to
leave you rather short changed by charging extra for optional (and
useful) features that come as standard with the SDS1202-E.

>
> Don't throw the boat anchor away until you are satisfied that the new
> scope can do everything you want at least as well as the boat anchor.

Well, I've just ventured into our basement (one time radio shack and
workshop that became a rather neglected facility when I went self
employed some 23 years ago) to take a look at this venerable "boat
anchor" to try and note make and model details and confirm its dual
beamness (my recollection of this feature is a little bit hazy to say the
least after some 20 years of neglect).

At first, I couldn't locate it from amongst the original inventory plus
the additional junk accumulated over the past two decades or so but more
careful scrutiny revealed its presence on the dexion shelving tucked
right into the back corner of the basement, a location where access is
currently blocked by a pile of junk heaped on the floor. It wasn't quite
as imposing a boat anchor as I'd been expecting and that with its matt
black paint job had helped camouflage it from my initial scan of the
dexion shelving.

Anyhow, I wasn't about to initiate another clear-out and I didn't want
to expend energy on merely moving the clutter to another part of the
basement so its spec remains a mystery for the time being. That corner of
the basement was the driest part so it's quite possible (exploding
electrolytics hazard aside) that it might still be in a serviceable
condition, assuming the HT windings on its BFO mains transformer haven't
succumbed to the very real possibility of 'green spot' failure (AFAICR,
the transformer(s) had all been impregnated with bitumen sealing compound
as was the practice of the day back in the 40s and 50s so might still be
'green spot' free even now).

AFAICR, its bandwidth was a mere 5MHz at best (certainly nowhere near
10MHz or above) so really only good for audio frequency work which is
what I'd really purchased it for way back in the early 70s (most likely
from my local WD surplus shop).

I'd been building a 200W RMS per 4 ohm load stereo PA amp of my own
unique design using ex main frame computer PSU parts (also from my local
WD surplus shop) and a cheap 'scope seemed like a useful item of test kit
to help me test my amplifier designing efforts.

The need to record wave traces led me via the art of oscillography into
a more general interest in photography since the 'weapon of choice' for
this work was the SLR camera. If nothing else, I have good enough reason
to hang onto this venerable bit of kit, even if only as a 'keepsake'
rather than bust a gut trying to get rid of it. :-)

Other than the initial oscillography, it never saw a lot of use.
However, its 1v 50Hz mains derived calibration test voltage did
eventually reveal that the slightly flat topped mains voltage waveform,
that I'd assumed was possibly an artefact of the BFO mains transformer's
loading or possibly an iron core saturation effect, turned out to be the
real waveform of the mains supply.

When I powered it up via my 2nd hand APC SmartUPS2000 2KVA/1500W line
interactive Pure Sine wave UPS and unplugged it from the mains supply to
switch over to battery power the visibly distorted sine wave magically
morphed into a perfect sine wave (with just a slight hint of the 5KSa/s
ripple from the class D inverter used to synthesise the sine wave output).

A little while later, when I was repeating this test of UPS and petrol
(gasoline) powered generator sine wave purity using Cool Edit Pro on a
laptop to record a sample of the mains voltage obtained using an old 6vac
wallwart transformer with resistor network attenuator into the line in on
the laptop's sound adapter's interface, I saw exactly the same waveforms
which neatly removed any question of 'transformer distortion' from the
equation.

It turns out the purity of the UK's national grid 50Hz sine wave supply
is somewhat lacking even when compared to that of a cheap 2.8KVA generator
[1]. For reference, it's more accurately best described as having a 'down
sloping' flat topped appearance (with respect to absolute amplitude -
it's an 'up-slope' on the negative peaks). I make this reference for the
benefit of those armed only with a cheap digital 'scope[2] that simply
shows a flat topping effect without any hint of a slope on the mains
waveform versus the more pure looking sine wave from a cheap 1KW Parkside
inverter generator (PGI 1200 B2).



[1] Curiously, the quality of the UPS's sine wave inverter output was
comparable to that of the single phase single pole pair generator head
used on the cheap 2.8KVA generator in that both exhibited a high
frequency (circa 5KHz) ripple superimposed on the 50Hz fundamental.

In the case of the generator this is an artefact known as 'slot winding
ripple'. In both cases, such high frequency ripple is of absolutely no
consequence to even the most fussiest of mains voltage power supplies
used by the most sensitive items of "Electronic Equipment".

What makes such cheap generators unsuitable for use with "Sensitive
Electronic Equipment"(tm) is their over-volting response to modest
amounts of capacitive loading, a characteristic that's totally absent
from inverter gensets, hence their suitability so often and (for once)
justifiably advertised, for use with such "sensitive equipment".

[2] For example the Rigol DS1052E being used here by Chris Howard
(callsign GOMTCH) in his youtube video of a test he did with a Parkside
PGI 1200 B2 inverter genset <https://youtu.be/JTTGvjbY8_s?t=403>

After identifying the scope being used in this youtube video, I was able
to google for reviews which revealed that it's a ten year old model
that's now long since passed its BBD. I did note a reference to an 8 bit
(256 levels) vertical resolution and the use of a 320 by 240 pixel screen
which just might account for it failing to accurately show the sloped
flat topping of the mains supply voltage in this video.

However, the fact that both this and the SDS1202X-E both have vertical
ADC resolutions limited to just 8 bits suggests the latter might also
fail to miss such subtleties as the sloped flat topping of the UK mains
voltage waveform that is so clearly and unambiguously displayed on a
classic CRO.

The doubled vertical resolution of the SDS1202X-E's 800 by 480 pixel
display might mitigate this shortcoming to some extent. This curious
stagnation of vertical resolution over the past decade probably explains
why there is still a fondness for the classic CRO and a lingering sense
of dissatisfaction with the new fangled DSO (at least at the entry level
end of that market segment).

Perhaps I should be looking out for the use of 10 and 12 bit vertical
resolutions in the specifications of any candidate DSOs that take my
fancy. No doubt there'll most likely be an added cost for such improved
resolution. :-(

--
Johnny B Good

[John Larkin]

On Sat, 27 Oct 2018 14:50:08 -0700, Joerg <ne...@analogconsultants.com>
wrote:

>On 2018-10-25 14:27, John Larkin wrote:
>>
>>
>> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>>
>> Other places have this box for $99.
>>
>>
>
>I have a no-name ARB because I needed one year ago for aerospace
>testing. The 1st one had a bum FPGA. Was replaced. The 2nd one now has a
>slowly failing rotary encoder. Oh well.

Even if they are junk, I can't understand how or why they would sell
all that for $99.

[tabb...@gmail.com]

If you're only doing audio the boat anchor should be plenty. It's 5x faster than my first scope. Or you could upgrade to the £11 DSO-138 with all of 200kHz bw :) Seriously, although that's beyond basic, it's also tiny enough and cheap enough to take to any job anywhere anytime.

I do that with multimeters, as well as decent ones I got a clutch of £2.34 ones that I can leave in potentially convenient places and take anywhere without concern. They've been handy in all sorts of situations where I would not have thought to take a proper meter.

For 100MHz there's a fair assortment of used scopes on ebay, some at good prices. And some definite horrors.


NT

[Tom Del Rosso]

They seem not to understand that they can make much better quality for a
little more money. It might be symptomatic of copying the design in the
first place.

[Tom Del Rosso]

Thanks, I suspected as much. There's still lots of room for improvement
in the software to cut the number of steps.

I assume the memories are so small because they used a small FPGA with
not enough address lines. That's another place where they could improve
it a lot for a few dollars.

[Tom Gardner]

On 27/10/18 23:07, Johnny B Good wrote:
> It turns out the purity of the UK's national grid 50Hz sine wave supply
> is somewhat lacking even when compared to that of a cheap 2.8KVA generator
> [1]. For reference, it's more accurately best described as having a 'down
> sloping' flat topped appearance (with respect to absolute amplitude -
> it's an 'up-slope' on the negative peaks). I make this reference for the
> benefit of those armed only with a cheap digital 'scope[2] that simply
> shows a flat topping effect without any hint of a slope on the mains
> waveform versus the more pure looking sine wave from a cheap 1KW Parkside
> inverter generator (PGI 1200 B2).

The "clipped sine wave" appearance surprised me, when I looked
at it for the first time since the 70s.

I believe it is because there has been a change in the loads
on the grid. Nowadays there are a large number of devices
with SMPSs. Many presume a more-or-less constant input voltage
throughout the mains cycle, so they rectify the and smooth the
mains, "topping up" the charge in the capacitor only at the
peak voltages. Hence significantly more current is drawn at
the peaks than at other parts of the cycle.

As for inverters (i.e. not petrol-driven generators), I
would be wary about applying a "modified sine wave" output
to valuable equipment. The PSU might be unfazed by such
rectangular input, but in cheap equipment, who knows.

[Martin Brown]

Presumably because they can make them in bulk for less than $80 and are
content with a rather small margin on each sale. I am tempted to get one
but so far I have resisted. Sooner or later I will find an excuse to
buy one and clutter up my equipment rack some more. I presume the model
of choice is the 14bit DAC version but which of the many "brands" of
identical spec kit is the original design or are they all made in one
factory and badged by the resellers (much like some LCD TVs).

--
Regards,
Martin Brown

[Jeroen Belleman]

All stuff *used to* do that. Welcome to the new age.

Jeroen Belleman

[Rob]

Tom Gardner <spam...@blueyonder.co.uk> wrote:
> I believe it is because there has been a change in the loads
> on the grid. Nowadays there are a large number of devices
> with SMPSs. Many presume a more-or-less constant input voltage
> throughout the mains cycle, so they rectify the and smooth the
> mains, "topping up" the charge in the capacitor only at the
> peak voltages. Hence significantly more current is drawn at
> the peaks than at other parts of the cycle.

More modern SMPSs should fix that by having PFC (Power Factor Correction).

It basically is an extra switching boost-converter in front of the main
capacitor operating from unsmoothed rectified mains, it converts the
half-sinewave voltage to a constant voltage to charge the capacitor.
(the working point of the converter is changing all the time in the
rhythm of the mains voltage)

Of course there still exists a lot of equipment without this, now
manadatory, feature. And it is not required for lowpower devices,
which become more and more prevalent.

[Tom Gardner]

What's not clear to me is whether the large number
of "low power" PSUs in domestic equipment is sufficient
to clip the peaks.

I'm open to other suggestions, of course.

[Piglet]

Not just SMPS, many mains transformers and motors go into soft
saturation near peaks. But in general I think it is more to do with the
large number of appliances within a few tens of metres of you - the
waveform on the HV grid pylons might be much purer?

piglet

[Carl]

Just browsing casually, in the 10-60 MHz range, going from $100ish to
$350ish seems to get you from 8 bits to 12, 14, or 16 bits, and from 8 KPts
to 1+ Mpts per waveform. www.saelig.com has a good selection of test gear
so it's easy to compare features there (I'm a satisfied customer, YMMV), but
there are more and more places to buy so price shop to your heart's content.

--
Regards,
Carl Ijames

[John Larkin]

On Sat, 27 Oct 2018 02:33:15 -0700 (PDT), speff <spe...@gmail.com>
wrote:

The analog scope will just show a solid rectangle of light when the
sweep is too slow for the waveform. I think a digital scope could do
that, with a bit of code, instead of aliasing. It could also intensity
weight on duty cycle, like an analog scope does.

One quickly learns to recognize the aliasing and crank up the sweep
rate.

[Phil Hobbs]

Lots of them do that now. It's a nice feature.

>
> One quickly learns to recognize the aliasing and crank up the sweep
> rate.

You can also just live in 'envelope' mode.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

[tabb...@gmail.com]

it's a somewhat effective way to get a scope to see signals above its frequency limit, doing the enveloping externally.


NT

[Phil Hobbs]

I prefer to just buy a faster scope. Why waste a nice excuse like that?
;)

I have scopes with bandwidths of 50 GHz (11801C), 20 GHz (11802), 3 GHz
(TDS 694C), two at 1 GHz (TDS 784A), and a number of slower ones. Fast
boat anchors are pretty cheap.

I would like one with serial decode eventually, but I rarely need that
sort of thing.

[Joerg]

Likely much less than $80. Even back in the early 90's we had Asian
pricing and rest of world (ROW) pricing. I learned that very quickly
when working in South Korea for the first time. Internet was in its
infancy so they had wallpapered a whole hallway with daily updated
computer printouts (remember the "tractor paper"?) and there was a
constant pilgrimage to that wll by design engineers. It's amazing how
low you can go if a transistor costs around one cent. They also did not
have the hugely expensive placement cost penalty that many Western
enterprises had to or sometimes still have to deal with.

What blew my mind was when in the mid-90's (!) someone showed the fully
burdened cost of a simple fax machine, from scratch to packaged product
with manual and all. That cost total was slightly under $7.

Profitably making and selling an ARB generator for around $100 is a
piece of cake for Asians. Especially since the R&D costs are often,
ahem, negligible.

[George Herold]

On Saturday, October 27, 2018 at 4:04:13 AM UTC-4, speff wrote:
> On Friday, 26 October 2018 20:53:56 UTC-4, tabb...@gmail.com wrote:
> > On Friday, 26 October 2018 23:26:30 UTC+1, speff wrote:
> > > On Friday, 26 October 2018 14:05:08 UTC-4, Carl wrote:
> >
> > > > grounding. It's on eBay for $110-120 depending on frequency range (20, 30,
> > > > 40, 60 MHz) so basically the same price. Interestingly, each frequency step
> > > > only adds about $2-3 to the price so I don't see why anyone wouldn't just
> > > > get the 60 MHz model.
> >
> > > China domestic retail pricing is almost exactly double for the 60MHz compared to 20MHz. That's for the original unit from the factory. Some (maybe most) of the eBay ones appear to be clones. I wonder if they cheaped out on the DAC.
> >
> >
> > you don't think they cheaped out on every bit?
> >
> >
> > NT
>
> The original manufacturer, probably not. They say they've sold more than 100K pieces.
>
> ------
> Listen to the advice of the majority of users, and strive to provide customers with friends with more convenient and easy to use high-performance, cost-effective products.
>
> Product upgrade!
>
> 1. Add AM, FM, PM, ASK, FSK, PSK modulation functions!
>
> 2. The phase adjustment resolution is upgraded to 0.01°;
>
> 3. The duty cycle adjustment resolution is upgraded to 0.01%;
>
>
> 4. The square wave rising edge and falling edge time are adjustable. When the instrument sets the square wave output, press the F4 button to switch between the duty cycle and the lifting edge time setting, thus making the instrument more applicable!
One of my sig gens' does square waves with adjustable edges, that can
useful.

GH
>
> 5, the use of silicone buttons and gold-plated button contacts, so that the instrument button life is longer, the operating feel is more comfortable.

[Cursitor Doom]

On Sat, 27 Oct 2018 02:33:15 -0700, speff wrote:

> My Tek battery powered digital scope lies to you if you set the sweep
> too slow for the signals.. there does not appear to be any anti-aliasing
> filter. Analog scopes don't lie in that particular disturbing manner.
>

Speff! Good to see you back again! And making great sense, too. We need
more of that here nowadays.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

[George Herold]

I've mostly been using cheaper stuff, that doesn't have that
feature. You turn it off and it forgets, and goes back to defaults.

Have you tried one of the new keysight 'scopes?
I have yet to find something to complain about..
and mostly I'm just amazed. I was doing single screen captures
bang... there's the event I'm looking for, now I need to see how
it ends, I turn the time base knob.. and low and behold the rest of
the signal is there!

George H.

[Tom Del Rosso]

Phil Hobbs wrote:
>
> I would like one with serial decode eventually, but I rarely need that
> sort of thing.

It should be possible to download the scope data to a PC and run a
freeware app to decode it.

[Johnny B Good]

On Sun, 28 Oct 2018 08:43:17 +0000, Tom Gardner wrote:

> On 27/10/18 23:07, Johnny B Good wrote:
>> It turns out the purity of the UK's national grid 50Hz sine wave
>> supply
>> is somewhat lacking even when compared to that of a cheap 2.8KVA
>> generator [1]. For reference, it's more accurately best described as
>> having a 'down sloping' flat topped appearance (with respect to
>> absolute amplitude - it's an 'up-slope' on the negative peaks). I make
>> this reference for the benefit of those armed only with a cheap digital
>> 'scope[2] that simply shows a flat topping effect without any hint of a
>> slope on the mains waveform versus the more pure looking sine wave from
>> a cheap 1KW Parkside inverter generator (PGI 1200 B2).
>
> The "clipped sine wave" appearance surprised me, when I looked at it for
> the first time since the 70s.
>
> I believe it is because there has been a change in the loads on the
> grid. Nowadays there are a large number of devices with SMPSs. Many
> presume a more-or-less constant input voltage throughout the mains
> cycle, so they rectify the and smooth the mains, "topping up" the charge
> in the capacitor only at the peak voltages. Hence significantly more
> current is drawn at the peaks than at other parts of the cycle.

That was my very first thought when I proved that the 50Hz 'Cal'
waveform was indeed a true reflection of the mains supply. This issue of
"Low PF loads by virtue of the narrow conduction angle" of the full wave
bridge rectifiers with capacitor smoothing in the HT modules of SMPSUs in
desktop PCs and more and more domestic kit which started to appear in the
mid 80s, became recognised by the regulatory bodies who enacted
regulations to force the manufacturers to address this problem by
including PFC circuitry in all new designs above a minimum power rating
(quite possibly the old 20W limit imposed on non PFC magnetically
ballasted fluorescent lamps - remember the Philips SL18 CFL, anyone?).

It's been quite a few years since I last recorded a mains supply
waveform for closer examination so the sloped flat topping effect might
not be quite so pronounced today. I've still got my mains voltage
sampling wallwart transformer to hand so that will be one of the first
things I'll be looking at with whatever DSO I finally decide to plump
for. :-)

>
> As for inverters (i.e. not petrol-driven generators), I would be wary
> about applying a "modified sine wave" output to valuable equipment. The
> PSU might be unfazed by such rectangular input, but in cheap equipment,
> who knows.

I use an APC BackUPS500 to protect my NAS box from outages effecting the
"Protected Supply" provided by the SmartUPS2000 in my basement. This is a
"quasi-sine wave" (modified square wave - a circa 330 Vpk square wave
with a 30% or so dead dead time between polarity reversals to approximate
a 240vrms supply for IT kit possessed of PSUs that couldn't give a toss
about "Sine-wave Purity"(tm).

The SmartUPS feeding the 'Protected Supply' is a line interactive type
meaning it passes the mains supply straight through, monitoring not only
for outright outages/brownouts and dangerous surges and spikes, but also
for the more modest sags and swells which it will boost or buck by
switching taps on its (rather weighty) mains transformers to condition
the supply voltage without resorting to running its sine wave inverter
and burning up precious battery charge/discharge cycle life.

The main charm of quasi sine-wave types of UPS is not only their low
price but also their lower running cost in terms of their 'maintainance
consumption'; in this case just under 3 watts versus the 32 to 35 watts
of the SmartUPS2000 and the 20W exactly of the smaller SmartUPS700
(700VA/450W) long since retired due to having the worst maintainance
consumption to protected capacity ratio of all of my UPSes.

However, such good maintainance consumption to protected power level
ratios aren't guaranteed to be as good as that 25 year old BackUPS500 so
beware of this the next time you go shopping for a cheap 'n' cheerful UPS
and ask to check the full manufacturer's specification, making it clear
if needs be (the manufacturers tend to be silent on this point) that if
it consumes more than 1% of its maximum wattage output capacity rating in
maintainance consumption (what it takes after fully recharging its
battery pack), you reserve the right to return it as "Not Fit For
Purpose".

As long as you restrict the use of such quasi sine-wave inverter based
UPSes to kit that you know for sure to be using an smpsu such as desktop
PCs etc, there's not really going to be a problem.

However, if you're powering a cheap LED lamp via such a supply to
provide a modicum of emergency lighting to avoid having to scrabble
around in the pitch black by the glow of only an indicator LED or two,
you may find yourself in the dark in short order anyway as the square
wave pulses passed by the dropper capacitor to the LED string either
kills the inrush limiter resistor (assuming the bean counters hadn't
decided it was an unnecessary luxury item that could be replaced with a
wire link) or else the LED string itself.

If you're going to use a cheap clip on lamp holder to provide emergency
lighting during an outage, your safest bet would be to pick one that'll
accept a 15W pygmy lamp (either that or keep a battery powered LED
lantern to hand for such emergencies).

--
Johnny B Good

[John Larkin]

And there are countries where you can buy CE stickers by the kilogram.

[Lasse Langwadt Christensen]

you have to get them from somewhere

[Johnny B Good]

On Sat, 27 Oct 2018 13:53:34 -0700, jjhudak4 wrote:

> On Friday, October 26, 2018 at 11:32:42 PM UTC-4, Johnny B Good wrote:

>> On Fri, 26 Oct 2018 13:27:07 -0700, Klaus Kragelund wrote:
>>
>> > A 200MHz scope for 379 USD:
>> >
>> >

>> I've been considering replacing my ancient 1950s CRT dual beam 70Lbs
>> 'scope with something more up to date recently and this Siglent
>> Technologies SDS1202X-E 'scope looked like it might be a good value
>> proposition (a snip at a mere £363.05 for UK customers via Amazon's
>> 'Fulfilment' delivery) so have checked out some reviews[1] which seem
>> to confirm this view.
>>
>> However, this is a subject of very recent interest so I haven't yet
>> researched this in any great depth as yet so I was wondering if you had
>> any advice on this 'scope or possibly better alternatives (100MHz B/W
>> dual trace at a minimum) that you could offer to aid me in my search
>> for a reasonably specced and priced unit?
>>

>> [1] Amazon customer reviews here:
>>
>> <https://www.amazon.co.uk/Siglent-Technologies-SDS1202X-
>> Oscilloscope-Channels/dp/B06XZML6RD/ref=sr_1_1?
>> ie=UTF8&qid=1540608976&sr=8-1&keywords=sds1202x-e>
>>
>> TinyURL <https://tinyurl.com/ydgpong6>
>>
>> (click the customer reviews link near the top of the page)
>>
>>
>> The Defpom's Repair Channel review videos here:
>>
>> <https://youtu.be/64kxGDOg7es?t=19> Part 1
>> <https://youtu.be/laK1v2Zas4o?t=12> Part 2
>>

>> --
>> Johnny B Good
>
> To each their own. When I wanted something a bit more portable than my
> Tek 7903 I got a used tek for ~$250 USD, spent some time cleaning it up
> and calibrating. Good as new. Not quite as glitzy but solid and
> serviceable.
>
> Some tek scopes have Tek specific ICs and modules that are very hard to
> find, but on the whole, very serviceable, if that be your inclination.
> Post your interest on the tek NG and you will receive some very useful
> info.
>
Thanks for that suggestion regarding the existence of a Tek News Group.
That's well worth adding to my NG list (at least we're *not* dealing with
some forum hosted on a shitty website). :-)

In the meantime, I've just tracked down the UK agent for Siglent
(labtronix.co.uk) who are selling the SDS1202X-E for a mere £365 with
free delivery (by virtue of it being over £70). Also, they mention that
they hold new stock with serial numbers which include the all important
"BB" characters signifying that they're not the earlier versions that had
been plagued by a probe compensation issue.

Since they *are* a UK company based in Loughborough, Leicestershire,
I've bookmarked their website as a potential supplier should I finally
settle on this 'scope for lack of a better alternative. However, this may
be one of those companies that only accept Paypal transactions... Just
checked out their Ts & Cs and this is the case.

I did set up a Paypal account several years ago but haven't used it and
have steadfastly refused to acknowledge the endless pleas to change my
account settings that I was receiving in my inbox every few months which
may or may not have been phishing attacks - ignoring them seemed the
safest policy since if genuine, the worst that could happen would be
Paypal suspending or deleting my account, either of which would have
suited me.

I'm not overly keen to reactivate the old account or create a new one so
it looks like I won't be buying from a company that doesn't support the
more mainstream methods of payment such as Visa and the like. Possibly
I'm being a little over-cautious in my steering clear of Paypal
involvement - should I be? The few Paypal transactions I had made had all
been successful, it was the emails about changes in their Ts & Cs and the
requests to log into my account to change my settings (and no doubt agree
to the new Ts & Cs) which rather put me off using Paypal for any more
online transactions. However, I might change my mind about this given
compelling enough reasons.

--
Johnny B Good

[tabb...@gmail.com]

several companies say they only take paypal, when really they accept debit/credit cards, they just use paypal to process them. You don't even need a paypal account to pay that way.


NT

[Johnny B Good]

On Sun, 28 Oct 2018 22:52:58 -0700, tabbypurr wrote:

> On Monday, 29 October 2018 02:40:29 UTC, Johnny B Good wrote:

====snip====

>>
>> I'm not overly keen to reactivate the old account or create a new one
>> so
>> it looks like I won't be buying from a company that doesn't support the
>> more mainstream methods of payment such as Visa and the like. Possibly
>> I'm being a little over-cautious in my steering clear of Paypal
>> involvement - should I be? The few Paypal transactions I had made had
>> all been successful, it was the emails about changes in their Ts & Cs
>> and the requests to log into my account to change my settings (and no
>> doubt agree to the new Ts & Cs) which rather put me off using Paypal
>> for any more online transactions. However, I might change my mind about
>> this given compelling enough reasons.
>
> several companies say they only take paypal, when really they accept
> debit/credit cards, they just use paypal to process them. You don't even
> need a paypal account to pay that way.
>

Thanks for that hint, NT. I'll try making an order to see what options
are *actually* available at the payment details stage of the transaction.

BTW, has anyone dealt with this company before? I haven't seen any
comments about Labtronix as a supplier. Just wondering whether anyone
here has any horror/good experience stories to relate in their dealings
with them.

--
Johnny B Good

[Johnny B Good]

On Fri, 26 Oct 2018 08:21:39 -0700, speff wrote:

> On Friday, 26 October 2018 06:40:37 UTC-4, Clifford Heath wrote:
>> On 26/10/18 7:42 pm, speff wrote:
>> > On Thursday, 25 October 2018 17:27:24 UTC-4, John Larkin wrote:
>> >> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-
Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?
ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%

252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>> >>
>> >> Other places have this box for $99.
>> >

>> > $99 would be a very good price, from what I can see, better than
>> > China list- looks like a more normal price would be about $150-$200
>> > in the US for the 60MHz version. The lower frequency versions are
>> > significantly cheaper.
>> >
>> > It appears to use an Altera Cyclone IV FPGA driving 14-bit DAC.
>> > 320x240 color TFT. This is NOT your hobbyist DDS chip.
>>
>> The prevalence of cloning in this kind of device is usually because
>> someone published the designs.
>>
>> It's often an advanced hobbyist. I have a couple of gadgets like this;
>> if you search hard enough you can find the original blog postings
>> showing where the design was developed. There are plenty of hobbyists
>> advanced enough to have developed this design.
>>
>> I haven't searched, but mere hardware copying wouldn't result in the
>> plethora of clones; the original software has to be published
>> somewhere. Otherwise the cloners would have to write it again
>> (differently) to accommodate any design changes, and that's too much
>> like hard work; they'd need to understand how what they were cloning
>> works.
>
> Googled it and there's a huge thread at EEVBLOG on this product.
>
> https://www.eevblog.com/forum/testgear/feeltech-fy6600-60mhz-2-ch-vco-
function-arbitrary-waveform-signal-generator/
>

Yeah, thanks (I think). I've just spent the last couple of hours reading
that thread and am only on page 8 (after having a quick peek at the last
10 pages to see how it petered out)!

My interest is motivated by my purchasing a "fy6600-60m" in the small
hours of this morning for £75.66 from an Ebay trader offering free[1]
delivery from a UK warehouse (delivery ETA 10th to 12th of this month).

This buying decision was prompted by several days of watching countless
Youtube reviews and teardown videos ad nauseum (I was resorting to not
only (briefly) watching repeats but also looking at Russian and German
language reviews). "You certainly have to kiss an awful lot of frogs to
find your prince.". In this case, I mostly found warty toads amongst the
'frogs' and the closest I came to finding a 'prince' was still a frog. :-(

The business with PSU mains frequency leakage from the smpsu used is
simply the price you pay to reduce the more obnoxious HF switching spikes
from polluting the DC rails - it's a fekin' compromise that none of the
moaning nincompoops seemed to properly understand.

Also, another stand out "moan of ignorance" was in regard of the DC
offset range interaction with the Pk2Pk voltage swing limits. Then there
was the even more staggering ignorance that you need to terminate a 50
ohm co-ax feed, fed from a 50 ohm signal source with... guess what? A
FIFTY OHM RESISTIVE LOAD!!! Gah! Even a radio ham fell into this trap. :-(

After finally satiating myself of all this low grade video evidence on
Youtube, I finally managed to conclude that this would be a suitably
cheaper alternative to the 360 quid Siglent SDG1032X Signal Generator I'd
been eyeing up on Labtronix.co.uk to go with my recently purchased
Siglent SDS1202X-E dual channel 200MHz 1Gsa/s DSO (also from Labtronix).

At a mere £75.66 postage free delivery within the week, I can easily
forgive its "shortcomings". For the money, it's excellent value, "warts
'n' all". That thread in EEVblog seems to offer ways and means by which
to sandpaper down the more objectionable warts - I have yet to finish
reading it. Still, it's something to help pass the time whilst I wait to
take delivery of my 'new toy'. :-)

The PSU leakage issue can be readily sorted - there's ample room to even
fit an inefficient analogue PSU should one so wish but a much better
solution, imo, is to use a decent smpsu that uses a transformer which
incorporates a shield between the HT and LT windings to avoid having to
resort to the bodge of a 5nF Y cap to ground the HF hash to half mains
voltage via another pair of Y caps which measure introduces the
possibility of damaging ESD sensitive electronic kit as a result of this
compromise.

Anyway, the EEVblog thread you linked to looks well worth reading,
especially now that I've paid my money and have an actual "fy6600-60m"
about to wing its way to me. :-)

[1] Unfortunately, the courier in this case is Royal Mail and their
tracking web page is still claiming "Tracking information is not
available for this service" which could mean that "goodlucksell" haven't
handed it over or, just as likely, Royal Mail haven't updated their
tracking system (or their tracking system is so slow, it's shit).

--
Johnny B Good

[Klaus Kragelund]

Thanks for the hint

I just bought one also. I have a HP33120 Arb, but it is single channel, and I need dual channel to do PWM signals for halfbridge drivers etc

Cheers

Klaus

[Johnny B Good]

Apologies for the tardy follow up but I decided to try ordering the
'scope from Labtronics the following day to see whether I could pay
without having to revive or create a paypal account and discovered the
Guest Paypal option which I chose to complete my order.

The 'scope arrived two days later and I've been a little preoccupied in
the six days since then gaining familiarity with 'My New Best
Friend' (that and dithering over whether to order a Siglent SDG1032X for
360 quid or go for the much cheaper FY6600-60M at a more disposable
£75.66 instead).

As you can probably imagine, such choices don't magically resolve
themselves these days without spending hours and hours checking out
Youtube review and tear down videos ad-nauseum until you can't find any
more new ones, no matter how hard you look, created by people with a
proper understanding of things like 'mains tingle voltage' from every
commodity SMPSU ever used without benefit of safety earth connection and
the importance of terminating a 50 ohm BNC cable with a 50 ohm resistive
terminator and so on and so forth.

When I have to read between the lines (more a case of looking past the
misunderstood misgivings which seem to pointlessly pad out a 10 or 15
minute video into an hour long treatise on how to modify this or that
aspect of the kit in question), that can be quite a few evenings (even
afternoons - really, most of the day but with natural breaks and lunch,
tea and supper breaks plus the odd household chore and food shopping
trip) worth of my time before I'm finally convinced I made the best cost/
performance trade off choice I possibly could (in the circumstances... I
reassure myself - I finally plumped for the FY6600-60M).

Said FY6600-60M is promised to reach me any day between Saturday and
Monday - Sunday seems unlikely, it's via Royal Mail so even Saturday
seems optimistic.

After spotting that the only difference in spec between the 30, 50 and
60 MHz versions lay in the upper sine wave frequency limit (all else
being identical), it did occur to me that the differences might simply
have been a matter of a firmware upgrade and possibly a couple of
capacitors or some such so I tried searching for a 60MHz hack for the
slightly cheaper 30MHz model.

Surprisingly, in view of the various mods referenced in the EEVblog
thread, none were forthcoming. However, with typically less than a tenner
price difference between the 30 and the 60MHz models, I wasn't too put
out.

An 8 to 10 quid price premium on the 60MHz model over the 30MHz one
seemed a fair enough price point but that hadn't stopped me from looking
for a possibly even cheaper option. Now that I'm satisfied I hadn't
overlooked an opportunity to pay even less for a 60MHz sig gen, I feel a
little happier over splurging that little extra on the 60MHz model. At
least it's ready to go without the faff of hacking a 30MHz unit, leaving
me to address just the other perceived shortcomings so roundly discussed
in the EEVblog here:

<https://www.eevblog.com/forum/testgear/feeltech-fy6600-60mhz-2-ch-vco-
function-arbitrary-waveform-signal-generator/>

Apologies if Pan has line wrapped the url. You can try the Tinyurl below
if it has.

<https://tinyurl.com/y9kydgwx>

I've got as far as the eighth page in that 69 page thread. I did have a
look at the last few pages to get a hint of just how long it had lasted.
However, "cutting to the chase" in a long thread like this isn't a
sensible idea when there seems to be some worthwhile discussion about
improving the product. I just might learn some useful things about my
next 'new toy'. :-)

--
Johnny B Good

[Neon John]

On Thu, 25 Oct 2018 14:27:15 -0700, John Larkin
<jjlarkin@highland_snip_technology.com> wrote:

>
>
>https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%252B7YiL&preST=_SX342_QL70_&dpSrc=srch

>
>Other places have this box for $99.

I bought that box about 2 months ago from a sleazebay vendor for $79
and free shipping. I am well-pleased so far.

John

John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

[Johnny B Good]

I'm not sure whether your thanks were directed to both speff's and my
posts combined or just mine alone but, in either case, your thanks are
appreciated anyway. :-)

>
> I just bought one also. I have a HP33120 Arb, but it is single channel,
> and I need dual channel to do PWM signals for halfbridge drivers etc
>

How recently? Are we talking days or weeks ago? Mine turned up just
after 10am Friday morning with the regular mail delivery, just over 50
hours after placing my order (it beat the deadline for earliest ETA by
two days and RM's tracking by several hours). For anyone interested, it's
sporting the 3.3 version of firmware (and the latest revision mainboard
as mentioned in the EEVblog).

I've been familiarising myself with its interface and discovering more
ways to become confused with my Siglent SDS1202X-E's features as well as
those of the FY6600-60M, hence my tardy response, not helped by my
plodding through the last dozen or so pages of that EEVblog thread.

I've added a 47K resistor across the low side resistor in the 10K+10K
potential divider network which drives the ref input of the adjustable
shunt reference chip which drives the opto-isolator in the PSU to raise
the 4.95v on the +5V line to 5.49v primarily so as to raise the +/-12v
rails by another volt to get them to circa 12.7v (+ & - rails) rather
than circa 11.7 volt.

It seemed a reasonable first mod to do since it was just a case of
soldering a pin through hole 1/8th watt resistor onto the underside of
the PSU board to bring the + & - 12v rails onto the better side of the
tolerance range (normally +/-10%). Total power consumption went up by
less than half a watt on its idling consumption of 5W ("Powered Down"
using its front panel "On/Off" button).

Even at maximum output with both channels driving 50 ohm dummy loads at
10MHz 20v p2p square wave, it draws just under 9W maximum off the mains
supply. Actually, after testing with and without the 50 ohm termination,
it looks like the output Z is more like 79 ohms than the claimed 50 ohms
(a claim also backed up by the pairs of 100 ohm resistors discovered by
DerKammi's reverse engineering of the circuit boards).

Open circuit versus 50 ohm loading of a 50 ohm impedance source should
only result in a drop down to 50% of the open circuit voltage, not a drop
down to 37.1% as I've just discovered. I've a sneaking suspicion that all
those 100 ohm resistors may turn out to be 150 ohm as per the TI
reference 150 ohm units of loading mentioned in their data sheets.

However, the fixing of such 'errors' (in this case, a simple matter of
shunting the 150 ohm resistors with 300 ohm resistors) is probably best
left to when the dual current feedback op-amp is upgraded to a pair of
seperate faster op-amp chips by those who feel the need to go against the
ill conceived 'wisdumb'[1] of "If it ain't broke, don't fix it!".

Adding a 47Kohm resistor to the PSU is a simple and easy to reverse mod
to correct for the voltages being on the wrong side of the tolerance
range. In this case, a little more voltage is "A Good Thing" in that it
gives the amps that extra margin against clipping.

I wouldn't bother about the other suggested mods to the PSU since the
10μF 450v HT smoothing cap is fine as it stands without replacing it with
a 68μF 400v one. After looking at several 'scrapped for spares'
'Universal' 100-240vac smpsus that I had to hand, the design rule appears
to be "Specify 1μF per watt of rated output power and no more" (and this
is for 'universal' smpsus designed to work off as low a mains voltage as
90vac rms!). For those of us blessed with 200 volt plus mains supplies,
the need to 'upgrade' that ht smoothing cap simply doesn't exist. :-).

Replacing 220μF 16v caps on the 12v lines with 25v versions is just
pointless. A much better option would have been to use 16v 470μF caps
instead if you'd really thought some improvement had been required (that
should half the 300mV or so of HF ripple I saw when I looked at the 12v
rails with my 'scope probes - the 16v rating simply isn't an issue, not
even if you push the rails to 15v!).

For the money, I think these signal generators are exceptional value,
warts and all. The nearest competing products by Siglent are five times
the price and more (and Siglent are at the cheap end of this market).
Most of the perceived shortcomings can be overcome using relatively
inexpensive mods.

However, the one shortcoming highlighted in the EEVblog forum that was
deemed the most seriously difficult to deal with was the matter of timing
jitter (in this case, a mere +/- 4ns). Right now, I'm looking at the
example traces in Siglent's features pdf of their sdg1000 series
generators showing how they've overcome this issue of jitter with their
'innovative EasyPulse Technology' and it seems to me that all they've
done is sacrifice 8ns of resolution by averaging two or three clocks'
worth of sampling to smear out that 8ns rise time over a nicely displayed
16 to 24 ns slope.

It strikes me that this 'innovative EasyPulse Technology' is being
oversold. For most hobbyist users, I think this feature may be largely
cosmetic. Anyone who finds such +/- 4ns of jitter troublesome would be
far better off building their own custom clock generators rather than
rely on a cheap general purpose sig generator anyway.

BTW, since I'm posting back into this thread, I think I aught to mention
that since my acquisition of a 'scope blessed by a DC coupling option
(both my boat anchor 'scope and the sound card I used to to examine our
50Hz 240vac supply wave-form had no such option), I have to take back my
earlier disparaging remarks about the Rigol 'scope I saw being used to
show the mains wave-form in a Youtube video demonstrating the features of
a Parkside inverter genset.

It turns out that the slope on the truncated tops of the 50Hz mains
supply voltage I'd witnessed had simply been an artefact of using AC
coupling with a significantly high (as far as 50Hz voltages are
concerned) HPF turnover frequency characteristic (circa 8Hz for the sound
card I believe and a rather unfortunate coincidence that a 50 years older
5MHz B/W boat anchor 'scope should seemingly share a similar HPF cut off
effect).

I saw exactly the same wave-form using my recently purchased Siglent
SDS1202X-E in the AC coupled setting but as soon as I selected the DC
coupled setting, this morphed into a flat topped sine wave with no hint
of any slope whatsoever. I feel so stupid for making such a sweeping
statement about the distortion on our UK mains supply. However in my
defence, until a week ago I hadn't the means to eliminate the HPF effect
on my "'scope plots". It just goes to show that it's never too late to
learn (given the right tools).

[1] There's seemingly no shortage of those so blind to the glaring yet
easy to fix defects in manufactured kit as to willingly subscribe to this
"If it ain't broke, don't fix it!" mentality to annoy those of us who can
see all to clearly such deficiencies. They're clearly related to those
who just keep getting in the way of those busily fixing all those
"impossible (or too expensive) to fix problems".

--
Johnny B Good

[Klaus Kragelund]

I ordered it on the 7th, seems it will come on the 13th, so effectively only 3 business days :-)

I will test mine, when it arrives, and write back

> However, the fixing of such 'errors' (in this case, a simple matter of
> shunting the 150 ohm resistors with 300 ohm resistors) is probably best
> left to when the dual current feedback op-amp is upgraded to a pair of
> seperate faster op-amp chips by those who feel the need to go against the
> ill conceived 'wisdumb'[1] of "If it ain't broke, don't fix it!".
>
> Adding a 47Kohm resistor to the PSU is a simple and easy to reverse mod
> to correct for the voltages being on the wrong side of the tolerance
> range. In this case, a little more voltage is "A Good Thing" in that it
> gives the amps that extra margin against clipping.
>
> I wouldn't bother about the other suggested mods to the PSU since the
> 10μF 450v HT smoothing cap is fine as it stands without replacing it with
> a 68μF 400v one. After looking at several 'scrapped for spares'
> 'Universal' 100-240vac smpsus that I had to hand, the design rule appears
> to be "Specify 1μF per watt of rated output power and no more" (and this
> is for 'universal' smpsus designed to work off as low a mains voltage as
> 90vac rms!). For those of us blessed with 200 volt plus mains supplies,
> the need to 'upgrade' that ht smoothing cap simply doesn't exist. :-).
>
> Replacing 220μF 16v caps on the 12v lines with 25v versions is just
> pointless. A much better option would have been to use 16v 470μF caps
> instead if you'd really thought some improvement had been required (that
> should half the 300mV or so of HF ripple I saw when I looked at the 12v
> rails with my 'scope probes - the 16v rating simply isn't an issue, not
> even if you push the rails to 15v!).
>

A lot of good info, must dig deeper into it. I guess I will only really do what is nessesary, is busy at work, so cannot spend much time on instrument tweeking

> For the money, I think these signal generators are exceptional value,
> warts and all. The nearest competing products by Siglent are five times
> the price and more (and Siglent are at the cheap end of this market).
> Most of the perceived shortcomings can be overcome using relatively
> inexpensive mods.
>
> However, the one shortcoming highlighted in the EEVblog forum that was
> deemed the most seriously difficult to deal with was the matter of timing
> jitter (in this case, a mere +/- 4ns). Right now, I'm looking at the
> example traces in Siglent's features pdf of their sdg1000 series
> generators showing how they've overcome this issue of jitter with their
> 'innovative EasyPulse Technology' and it seems to me that all they've
> done is sacrifice 8ns of resolution by averaging two or three clocks'
> worth of sampling to smear out that 8ns rise time over a nicely displayed
> 16 to 24 ns slope.
>

Just today I was doing a test on the HP 33120A, and it has 25ns rise time, so couldn't complete my test. The FY6600 is about 7ns, so a lot better, 10 times cheaper :-)

> It strikes me that this 'innovative EasyPulse Technology' is being
> oversold. For most hobbyist users, I think this feature may be largely
> cosmetic. Anyone who finds such +/- 4ns of jitter troublesome would be
> far better off building their own custom clock generators rather than
> rely on a cheap general purpose sig generator anyway.
>

Yes, use it where it makes sense :-)

Regards

Klaus

[Johnny B Good]

====snip====

>> >> At a mere £75.66 postage free delivery within the week, I can
>> >> easily
>> >> forgive its "shortcomings". For the money, it's excellent value,
>> >> "warts 'n' all". That thread in EEVblog seems to offer ways and
>> >> means by which to sandpaper down the more objectionable warts - I
>> >> have yet to finish reading it. Still, it's something to help pass
>> >> the time whilst I wait to take delivery of my 'new toy'. :-)
>> >>

====snip====

>> >>
>> >> Anyway, the EEVblog thread you linked to looks well worth reading,
>> >> especially now that I've paid my money and have an actual
>> >> "fy6600-60m" about to wing its way to me. :-)
>> >>

====snip====

>> > Thanks for the hint
>>
>> I'm not sure whether your thanks were directed to both speff's and my
>> posts combined or just mine alone but, in either case, your thanks are
>> appreciated anyway. :-)
>>
>>
>> > I just bought one also. I have a HP33120 Arb, but it is single
>> > channel, and I need dual channel to do PWM signals for halfbridge
>> > drivers etc
>> >
>> >
>> How recently? Are we talking days or weeks ago? Mine turned up just
>> after 10am Friday morning with the regular mail delivery, just over 50
>> hours after placing my order (it beat the deadline for earliest ETA by
>> two days and RM's tracking by several hours). For anyone interested,
>> it's sporting the 3.3 version of firmware (and the latest revision
>> mainboard as mentioned in the EEVblog).
>
> I ordered it on the 7th, seems it will come on the 13th, so effectively
> only 3 business days :-)

Well, seeing as it's now the morning of the 14th (I've been pondering
cost effective ways and means of improving my new toy - rereading the
EEVblog from start to finish... again! - and I had to get up early to put
our wheelie-bin out 'cos I forget to do so last night, therefore my being
up at what I usually regard as "Silly O'clock in the morning.", hence
this delayed response), I suspect you may well have had a chance to gain
some hands on experience by now. :-)

One handy "shortcut setting" that's well worth remembering is the, "One
long press of the "OK" button (the rotary knob) until it beeps", one
which stores the current settings of the two channels (freq/amplitude
etc) to use as subsequent power on defaults. That can be a real time
saver at the start of your next session.

>
>> I've been familiarising myself with its interface and discovering more
>> ways to become confused with my Siglent SDS1202X-E's features as well
>> as those of the FY6600-60M, hence my tardy response, not helped by my
>> plodding through the last dozen or so pages of that EEVblog thread.

One of the things I was having trouble with was my tendency to press the
on screen icons of the soft menu rather than the actual buttons. A
strange affliction considering I had no such problem with the soft menu
buttons on the Siglent 'scope - I guess the tiny screen on the FY6600
must be the main factor in this case.

>>
>> I've added a 47K resistor across the low side resistor in the 10K+10K
>> potential divider network which drives the ref input of the adjustable
>> shunt reference chip which drives the opto-isolator in the PSU to raise
>> the 4.95v on the +5V line to 5.49v primarily so as to raise the +/-12v
>> rails by another volt to get them to circa 12.7v (+ & - rails) rather
>> than circa 11.7 volt.
>>
>> It seemed a reasonable first mod to do since it was just a case of
>> soldering a pin through hole 1/8th watt resistor onto the underside of
>> the PSU board to bring the + & - 12v rails onto the better side of the
>> tolerance range (normally +/-10%). Total power consumption went up by
>> less than half a watt on its idling consumption of 5W ("Powered Down"
>> using its front panel "On/Off" button).

One of my "cost effective mods" I've researched since then has been
going through my collection of scrapped smpsu parts, notably the high
speed low Vf rectifier diodes as replacements of the mis-identified by
ebel0410 "LT7506"s which are actually FR107s, a cheap high speed version
of the classic 1N4007 1A rectifier diode. His replacements, 1N5819s, were
hardly any improvement despite being high speed 3A rated diodes.

I picked out all the likely candidate shotky rectifier diodes from my
collection and checked them out on my DVM's diode/continuity buzzer
setting. this passes a constant 1mA test current through the DUT and
shows a reading corresponding to the diode's Vf in millivolts. Standard
silicon diodes show, as one might well expect, values of 550 to 600,
depending on their current ratings.

My candidate diodes ranged from a low of 141 (ESAD83-004R) to a high of
247 with one of a candidate pair (MBR3045CT) at 201. The FR107s I'd
removed from the PSU board measured a whopping 518/520 on my DVM. Looking
at all the diode data sheets I downloaded, I thought I might see an extra
half volt improvement by shoehorning a couple of these TO220 dual diodes
onto the PSU's circuit board but I got a little more than I bargained for
with the positive rail going up again from the previously boosted 12.78
to 13.8 volts with the slightly less loaded negative rail going up by a
similar amount to just over 14 volts.

>>
>> Even at maximum output with both channels driving 50 ohm dummy loads
>> at
>> 10MHz 20v p2p square wave, it draws just under 9W maximum off the mains
>> supply. Actually, after testing with and without the 50 ohm
>> termination, it looks like the output Z is more like 79 ohms than the
>> claimed 50 ohms (a claim also backed up by the pairs of 100 ohm
>> resistors discovered by DerKammi's reverse engineering of the circuit
>> boards).

Subsequent testing after the diode upgrade revealed a very slight but
definite reduction in this maximum power consumption (about a 100mW's
worth) which is a rather reassuring result after applying such a
modification to an SMPSU. :-)

>>
>> Open circuit versus 50 ohm loading of a 50 ohm impedance source should
>> only result in a drop down to 50% of the open circuit voltage, not a
>> drop down to 37.1% as I've just discovered. I've a sneaking suspicion
>> that all those 100 ohm resistors may turn out to be 150 ohm as per the
>> TI reference 150 ohm units of loading mentioned in their data sheets.
>>
>>
> I will test mine, when it arrives, and write back

I've since done some more testing and it seems the output Z is close to
the 50 ohm mark after all. The big problem here is the use of a dual high
voltage CFB opamp (THS3002I which Texas Instruments refused to
acknowledge the existence of the variant used by Feeltech!) which might
have been fine in the first 15MHz model but which has now been pushed to
its limits and way beyond with the 25, 30 and 60MHz models.

The presence of unpopulated chip locations (U21 and U22) indicates that
Feeltech must have considered their frequency upgrade options and the
need to upgrade that dual high voltage CFB opamp to a higher performance
pair of single opamp chips, notably the THS3001 or THS3095 (or, now that
TI have produced an even higher spec version of the 3095, the THS3491).

The PSU mod is all well and good (any mod that improves an SMPSU's
efficiency can only be "A Good Thing"(tm) imo) but in this case, it's
rather wasted on the THS3002I dual opamp chip that Feeltech neglected to
upgrade to match the ever increasing demands of the later -25MHz to
-60MHz models.

The next obvious no-brainer modification (after all, you did choose a
60MHz model to at least provide 40 to 60 MHz 20V pk2pk *sine* waves...
didn't you?) is to replace that dual opamp chip with a pair of THS3001s
(or THS3095s or even THS3495s). Unfortunately, unlike the PSU diodes mod,
this one is unlikely to be satisfied by a change of BoMs using recycled
parts and will cost anywhere from £17.68 (a pair of THS3095DDAR from
China) and upwards to 40 quid or so in an order for a pair of opamp chips
from Digikey or Mouser.

A pair of 3091s will do nicely (the 3495s are a little OTT for 60MHz 20v
Pk2Pk sine wave duty and have the same minor issue of dealing with the
surplus to requirements Vref and /PD pins which also curse the 3095 chip).

Either of those three chip options will provide a much overdue
performance upgrade but try as I might, I can't see me satisfying my
requirement for under 33 quid which represents an extra 43.62% of the
price I'd paid for the FY6600 in the first place. I think that's one mod
best left on hold for the time being (at least until I've exhausted all
other possibly cheaper alternatives that might become available with a
little more research).


=====snip=====

And there you've discovered its attraction to the cost conscious
purchaser. A better performing (with some caveats) and cheaper version of
all those hideously expensive mainstream contenders. :-)

--
Johnny B Good

[John Miles, KE5FX]

On Wednesday, November 14, 2018 at 5:51:17 AM UTC-8, Johnny B Good wrote:
> The presence of unpopulated chip locations (U21 and U22) indicates that
> Feeltech must have considered their frequency upgrade options and the
> need to upgrade that dual high voltage CFB opamp to a higher performance
> pair of single opamp chips, notably the THS3001 or THS3095 (or, now that
> TI have produced an even higher spec version of the 3095, the THS3491).
>

Hmm, that's an interesting part. I hadn't run across it before. Basically
a higher-power LMH6702. That might save me a couple of relays.

-- john, KE5FX

[Johnny B Good]

JOOI, I took a look at the data sheet for that part. I thought a search
on that part number might lead me to a cheaper alternative (the best
price for a pair of THS3491IDDs that I've found so far has been £27.36
(including the VAT and free delivery) from Farnell/Element14).

Obviously, as far as upgrading the FY6600 to a better CFA high voltage
opamp is concerned, its low voltage rail (+/-6v max) precludes it from
further consideration. If you're thinking of using the THS3491 as a
replacement to an existing LMH6702, you'll have to increase the supply
rail voltages to a minimum of +/-7v (14v single rail).

In the meantime, I'm still pondering the wisdom of upgrading a cheap
£75.66 ARB sig generator to a £103.02 version that'll give much cleaner
looking 60MHz sine waves at 20v Pk2Pk.

Thinking about it, a £103.02 spend on a cheap ARB with a decent 60MHz
sine wave output is still bargain basement territory. I'd just like to be
certain that I hadn't overlooked a cheaper source for those opamp chips
before placing an order with Farnell/Element14 is all. :-(

Ah, to hell with the expense! I've just reviewed my previous post and
Farnell/Element14 have been the cheapest source I'd been able to track
down - there simply aren't any cheap Chinese sources showing up at all,
so I've no further choice in the matter of supplier anyway, it's either
Farnell/Element14 or not at all.

I've just ordered the opamps!

--
Johnny B Good

[Klaus Kragelund]

I just got mine today, and did some initial testing:

Risetime is 7ns as promished

Level setting is peak peak amplitude, not just amplitude

Output falls off above 5MHz for sine at 100mV amplitude. So cannot trust signal amplitude above 5MHz

For 5V amplitude, it falls of at about 15MHz

For square wave, it falls off at 25MHz, but of course the 7ns risetime means the signals are not really square

For 5V pulse, I can generate a pulse with about 10ns width. It's why I bought it, so great :-)

Annoying is that the unit weighs so little and the pushbuttons needs significant force, so I am pushing it off my instrument shelf. Really annoying

Also annoying that it does not have digit input for frequency. Must scroll a lot

Nice display though

Good performance for the price

Cheers

Klaus

[Johnny B Good]

It's a question of which parameter is the most consistent and the need
for brevity. :-( It doesn't take long to adjust to this abuse of the
definition of "Amplitude". :-)

>
> Output falls off above 5MHz for sine at 100mV amplitude. So cannot trust
> signal amplitude above 5MHz

I don't see such a fast drop off, maybe 3dB down at 60MHz versus 10MHz
down to 5Hz at the 5V Pk2Pk (AMPL) setting. I expect this to improve once
I've installed the THS3491 opamp chips.

I'm testing with a Siglent SDS1202X-E DSO using the 'scopes own 200MHz
rated probes on the 10 to 1 setting, plugged straight into the output
sockets via the BNC probe tip adapters. If you're using quality 50 ohm BNC
patch leads of any length, you need to terminate the 'scope or LMS end to
suppress reflections which would otherwise mess up your measurements.

>
> For 5V amplitude, it falls of at about 15MHz
>
> For square wave, it falls off at 25MHz, but of course the 7ns risetime
> means the signals are not really square

It's simply physically impossible to generate "Perfect Square Waves".
The best you can hope for when pushing right up to the upper frequency
limit, is a reasonable approximation to trapezoidal with minimal
'ringing' artefacts.

The frequency response is the same for sine, square and triangle waves
(50% duty cycle of course) at the 5v AMPL setting. For other, more
complex waves, all bets are off on their frequency plots once you go
above 10MHz (at least with the incumbent THS3002 opamp in residence).

>
> For 5V pulse, I can generate a pulse with about 10ns width. It's why I
> bought it, so great :-)
>
> Annoying is that the unit weighs so little and the pushbuttons needs
> significant force, so I am pushing it off my instrument shelf. Really
> annoying

Yeah, that's the problem with modern measuring instruments these days,
no gravitas whatsoever. Even the one time champion of "Gravitas",
Tektronix, is no better than any of its much cheaper Chinese made rivals
these days - I suspect that's because even Tektronix kit is now also of
Chinese manufacture (yet they still get away with charging an order of
magnitude more for what is essentially rebadged commodity DSO and ARW
generator kit of Chinese manufacture).

For those obsessed by the very real risk of zapping the chips in a DUT
[1] from the half mains Hi Z voltage that's ever present should you
neglect to bond the BNC shields to the ground reference of the DUT in
question, there's considerable merit in swapping out the original smpsu
for a case filling analogue PSU with its massive transformer and
smoothing caps and regulator chip heatsinks just for the extra gravitas
(weight) alone that this would bestow upon the FY6600[2].

Personally speaking, if I want to lend my generator additional gravitas,
I've got a roll or two of roofing lead I can use to fill in the gaping
void behind the display panel (and remove the useless tilt bar - the rear
rubberised feet are set so far from the back edge that tilting the front
up raises the rear feet clear of the work surface as it sits on the back
edge of the case and the non-rubberised tilt bar - slippy hard surfaces
all round!).

In fact, I'm rather inclined to unclip that tilt bar except for the fact
that it'll reduce its gravitas just a tad - I'll leave it until I've
added the missing ballast. :-)

OTOH, I might simply fit extra rubberised feet on the very back edge of
the case and rubberise the tilting bar to defeat its current tendency to
skate all around the worktop whenever it's propped up like this.

>
> Also annoying that it does not have digit input for frequency. Must
> scroll a lot

Yes, a Hell of a lot! :-( It wouldn't be so bad if the select buttons
weren't so awkward to reach and operate (they need a lot of pressure in
just the right spot before they register the button press).

>
> Nice display though

You must have younger eyes than mine (or a better prescription of bi/tri/
vari focals). I find it's a little too bijou for my taste. However,
ignoring the need to be able to accurately focus on the screen, it does
have sufficient pixels for the job (coincidentally, the same number as in
the Tektronix TPS2014B's physically larger display[3]). It's just a pity
that they couldn't have been spread out over a larger screen area, say a
20 to 25 percent larger diagonal.

There's just room to accommodate such a larger display option with a
little rearrangement of the LHS panel buttons and the RHS soft menu
buttons (or better yet, a touch screen to eliminate those five pesky
physical Function buttons). Of course, this is all added cost so little
chance of seeing such "cosmetic" improvements - what you do expect at
this price?

>
> Good performance for the price

Ergonomics aside, the performance is remarkably high for its price even
before its target market demographic succumb to the urge to "Fix It"
despite it not being seriously broken so as to improve it even further
(out of all recognition of its original OOTB performance in fact).


[NOTES]

[1] The 1nF switching hash suppression cap might represent a very Hi Z at
50/60Hz sine but the problem isn't the microamps of mains voltage
leakage, it's the high amperage transient discharge of a peak voltage
that can range from 85 to 170 volts from said capacitor into a poor
defenceless gate ESD protection diode (or worse still, a gate bereft of
any such diode protection).

[2] I think the best way to solve this issue of half live mains is to use
a simple 1:1 15VA 240vac isolating transformer between the incoming mains
socket and the original smpsu. If possible, use a split bobbin type of
transformer to minimise the stray leakage capacitance between windings to
just a few dozen pF.

However, even the classic single bobbin construction with insulation
tape layers separating the windings should keep the stray capacitance to
less than 100pF. If you pick a good quality transformer, you can keep the
additional transformer losses below the half watt mark. Alternatively,
you could contrive an external floating mains supply using a pair of 30VA
or larger transformers wired "Back to Back" via their secondary windings.
That gives you half the capacitive stray leakage of a single transformer
arrangement.

For instance, use a pair of 48VA rated 12-0-12 secondary with split 120v
+ 120v primary windings transformers wired back to back via the hot ends
of the 12-0-12 secondary connections, earthing the centre tap of the
second transformer's secondary and series up the 2nd (output)
transformer's split primary to provide the floating 240v mains feed to
the FY6600 with a 2M high voltage resistor linking the centre tap to
ground to act as a static drain. This will give you a low 'half mains'
leakage voltage worst case 60v ac with a maximum of 30 microamps and just
a few pF of leakage with a very low ESD risk.

Of course, all this could have been neatly sidestepped if the smpsu
transformer had incorporate an electrostatic screen between the primary
and secondary windings which could have been connected to the virtual
ground of the HT rectifier circuit, leaving the secondary side totally
disconnected from the half mains voltage via that mandated 1 to 5 nF EMI
suppression capacitor.

There'd still be some capacitive coupling to the half mains voltage of
the virtual ground but instead of a 1000pF's worth or more, it would have
been just a few pF's worth via the shield foil and the secondary winding,
reducing the coupling by around two orders of magnitude.

[3] I was quite shocked at the recent sight of a (presumably vintage -
there's a CF slot under the display FFS!) Tektronix TPS2014B DSO shown
here:

<https://www.dropbox.com/s/d84aqn62vmn13gd/P330_Jitter.jpg?dl=0>

It looked like a less 'polished' version of a Siglent SDS1204X-E DSO
selling in the UK for a mere 700 quid versus a rather horrific £4200 plus
VAT brand new from Farnell/Element14 (£5,040.00 VAT inclusive - over 7
times that of the Siglent's price!). I find it hard to believe that
anyone would want to blow that much money on Tektronix kit these days.

--
Johnny B Good

[John Miles, KE5FX]

On Wednesday, November 14, 2018 at 10:40:45 PM UTC-8, John Miles, KE5FX wrote:
> Hmm, that's an interesting part. I hadn't run across it before....

A few noise measurements:

http://www.ke5fx.com/ths3491.htm

-- john, KE5FX

[Winfield Hill]

John Miles, KE5FX wrote...

>
> On November 14, 2018, John Miles, KE5FX wrote:
>> Hmm, that's an interesting part. I hadn't run
>> across it before....
>
> A few noise measurements:
>
> http://www.ke5fx.com/ths3491.htm
>
>-- john, KE5FX

Thanks! That's a fascinating opamp. I imagine
it's not too hard to get carried away, and put
it into thermal limiting! I take it the Adoner
FY6600 ARB uses that for its output driver?

I see they claim 10Vp-p output at 320MHz, and
20Vp-p at 100MHz into 100 ohms. Very nice!


--
Thanks,
- Win

[bill....@ieee.org]

On Sunday, October 28, 2018 at 7:43:22 PM UTC+11, Tom Gardner wrote:
> On 27/10/18 23:07, Johnny B Good wrote:
> > It turns out the purity of the UK's national grid 50Hz sine wave supply
> > is somewhat lacking even when compared to that of a cheap 2.8KVA generator
> > [1]. For reference, it's more accurately best described as having a 'down
> > sloping' flat topped appearance (with respect to absolute amplitude -
> > it's an 'up-slope' on the negative peaks). I make this reference for the
> > benefit of those armed only with a cheap digital 'scope[2] that simply
> > shows a flat topping effect without any hint of a slope on the mains
> > waveform versus the more pure looking sine wave from a cheap 1KW Parkside
> > inverter generator (PGI 1200 B2).
>
> The "clipped sine wave" appearance surprised me, when I looked
> at it for the first time since the 70s.
>

> I believe it is because there has been a change in the loads
> on the grid. Nowadays there are a large number of devices
> with SMPSs. Many presume a more-or-less constant input voltage
> throughout the mains cycle, so they rectify the and smooth the
> mains, "topping up" the charge in the capacitor only at the
> peak voltages. Hence significantly more current is drawn at
> the peaks than at other parts of the cycle.

I'm not sure where the limit is now, but it used to be that if you were drawing more than 100W from the grid you had to build "power factor correction" into the front end of your power supply, which extracted a more or less sinusoidal current into a capacitor which fed your high-frequency inverter with a more or less constant high DC voltage - it obviously had to end up with enough 100Hz ripple to cope with delivering a more or less constant current while getting something like a rectified mains sine wave current.

Smaller stuff - like the ubiquitous wall warts - could get away with clipping the top off the sine wave.

> As for inverters (i.e. not petrol-driven generators), I
> would be wary about applying a "modified sine wave" output
> to valuable equipment. The PSU might be unfazed by such
> rectangular input, but in cheap equipment, who knows.

A proper modified sine wave has no third harmonic component, not a lot of fifth harmonic component but everything above that is just as bad as it would be in a square wave. You could filter quite a bit of that out, but a fancier inverter might be cheaper.

Higher harmonics are good for warming up iron cores.

--
Bill Sloman, Sydney