The HP 3561A - still useful in 2022?

[bitrex]

It's a cheap and cheerful (relatively compact) boat anchor, I'm curious
if it could be good for doing any useful low-frequency control system
loop analysis a la:

<https://www.hpmemoryproject.org/an/pdf/an_243-6.pdf>

Unfortunately it only seems to include some kind of shaped noise as a
source for gain/phase measurement but might still be useful for some
stuff.. The beefier 3562 included a curve fitting algorithm to fit an
s-domain transfer function to the gain/phase response automatically but
nowadays I think you could just dump the data to Matlab/Simulink and do
a better job of it anyway

Here's the specs for 3561A:

<https://82fai3h5wg8220a0l3ilfiz1-wpengine.netdna-ssl.com/wp-content/uploads//2015/09/HP3561A.pdf>

[Phil Hobbs]

Haven't used one of those since about 1988. The two-channel ones are
much better. I used to have a 3562A, which I liked a lot, and a 36660
that I didn't like as well because it used one digitizer for both
channels, so that it only went up to 50 kHz in two-channel mode.

I now have a 35665A, which I paid $300 for. It has the same problem but
has extra functionality. BTW there used to be an outfit called GLK
Instruments that would sell you a customized ROM that turned on all the
options. (I have one--it was $50 IIRC.)

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

[bitrex]

On 1/7/2022 10:52 AM, Phil Hobbs wrote:
> bitrex wrote:
>> It's a cheap and cheerful (relatively compact) boat anchor, I'm
>> curious if it could be good for doing any useful low-frequency control
>> system loop analysis a la:
>>
>> <https://www.hpmemoryproject.org/an/pdf/an_243-6.pdf>
>>
>> Unfortunately it only seems to include some kind of shaped noise as a
>> source for gain/phase measurement but might still be useful for some
>> stuff.. The beefier 3562 included a curve fitting algorithm to fit an
>> s-domain transfer function to the gain/phase response automatically
>> but nowadays I think you could just dump the data to Matlab/Simulink
>> and do a better job of it anyway
>>
>> Here's the specs for 3561A:
>>
>> <https://82fai3h5wg8220a0l3ilfiz1-wpengine.netdna-ssl.com/wp-content/uploads//2015/09/HP3561A.pdf>
>>
>
> Haven't used one of those since about 1988.  The two-channel ones are
> much better.  I used to have a 3562A, which I liked a lot, and a 36660
> that I didn't like as well because it used one digitizer for both
> channels, so that it only went up to 50 kHz in two-channel mode.
>
> I now have a 35665A, which I paid $300 for.  It has the same problem but
> has extra functionality.  BTW there used to be an outfit called GLK
> Instruments that would sell you a customized ROM that turned on all the
> options.  (I have one--it was $50 IIRC.)
>
> Cheers
>
> Phil Hobbs
>

Thanks, I have a USB/PC-based VNA that works well enough for the small
amount of RF stuff I do. But for low-frequency analyzers the options
seem more limited. The 3577A seems like the most general-purpose tool
but a certified refurb runs about 2k and then probably another 2k for
the S parameter test set which seems nice to have but I don't know how
often I'd use it...I may just keep my eye out for a working 3562 for
around 1k that doesn't seem unreasonable for what you get.

My short list for lab upgrade this year is a low-frequency analyzer and
a nice bench LCR meter/component analyzer but I tend to get deep in a
hole looking at the options, I don't really want to spend even $300 on
this kind of Shenzen-special stuff:

<https://www.amazon.com/East-Tester-Capacitance-Resistance-100hz-10KHZ/dp/B08FR2GB92/>

But then pretty quickly you're pushing several grand or more for units
from BK, etc.

[bitrex]

There's also the HP 3563A "Control System Analyzer" which seems like a
pretty useful piece for LF gain/phase also. HP stuff from this era is
weird it seems like there's a lot of cross-over and you could turn some
tools into any other tool just through options and ROM packages...

[boB]

These were awesome instruments in their time !

I would love to have one just for nastalgic reasons cuz we used to use
these in the 80s.

boB

[bitrex]

Mainly looking for a tool for profiling e.g. power inductors and audio
transformers, plus some control loop analysis. I'm not sure the 3561 is
the best tool perhaps, the lack of swept-sine and other signal injection
types is kind of a bummer.

The 3562 and 3563 seem like more appropriate tools for that job. There's
a spot down the road from me that carries a lot of this stuff surplus
and not paying shipping would be great, I'm planning on picking up a
3478A and a power supply or two there shortly:

<https://www.bmisurplus.com/product/hewlett-packard-hp-3478a-digital-multimeter/>

I'll ask if they ever get some of those two in stock, a G seems a fair
price for one in as-is working condition.

There was a 3561A on eBay for $200 plus shipping recently but someone
grabbed it first. It was functional but throwing a level 1 error code
and I looked it up, like "DMA writeback time violation" or somesuch.
That doesn't sound necessarily trivial, a bad memory board or IC to hunt
down perhaps. Don't really want to fuss with it...

[bitrex]

Getting these calibrated to a high standard is pretty cheap, like 50
bucks per unit.