Cheap and cheerful bench power supply

Trevor Wilson

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Jun 11, 2015, 12:00:30 AM6/11/15

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I'm looking for a cheap and cheerful bench power supply. Here are the
desired specs:

50-0-50 Volts, variable.
0-3 Amps, variable.
Tracking

Ideally, I would like:

0-5 Amps
Linear rather than SMPS
230/240VAC

The last three are not deal-breakers though. I've seen a few on eBay,
but am not certain about quality. Like this:

http://www.ebay.com.au/itm/Dr-Meter-HY5005E-2-SWITCHING-DUAL-DC-POWER-SUPPLY-50V-5A-Variable-/221422197471?pt=LH_DefaultDomain_0&hash=item338dca9adf

It would be nice to find one here in Australia, but 30-0-30 seems to be
the limit for the popular choices.

--
Trevor Wilson
www.rageaudio.com.au

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Trevor Wilson

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Jun 11, 2015, 12:05:02 AM6/11/15

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On 11/06/2015 1:58 PM, Trevor Wilson wrote:
> I'm looking for a cheap and cheerful bench power supply. Here are the
> desired specs:
>
> 50-0-50 Volts, variable.
> 0-3 Amps, variable.
> Tracking
>
> Ideally, I would like:
>
> 0-5 Amps
> Linear rather than SMPS
> 230/240VAC
>
> The last three are not deal-breakers though. I've seen a few on eBay,
> but am not certain about quality. Like this:
>
> http://www.ebay.com.au/itm/Dr-Meter-HY5005E-2-SWITCHING-DUAL-DC-POWER-SUPPLY-50V-5A-Variable-/221422197471?pt=LH_DefaultDomain_0&hash=item338dca9adf
>
>
> It would be nice to find one here in Australia, but 30-0-30 seems to be
> the limit for the popular choices.
>

**I found this at Element14:

http://au.element14.com/tenma/72-10500/power-supply-2ch-30v-3a-adjustable/dp/2251948

I wonder how difficult it would be to hack two of these to provide tracking:

https://www.rockby.com.au/Rockby/Mailer/RH_42287_1.htm#42287

I imagine that Wavecom is the manufacturer for Tenma. Possibly someone
has hacked these things?

captainvi...@gmail.com

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Jun 11, 2015, 2:08:35 AM6/11/15

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I would want my bench power supply to be as quiet as possible. Who cares about efficiency when you're designing and powering up a prototype. You may wind up with a switcher in the final design but I would definitely not get a switcher frr new product evaluation. Lenny.

Phil Hobbs

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Jun 11, 2015, 11:19:19 AM6/11/15

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Switchers plus cap multipliers are pretty good. If you're willing to
spend a volt or two of headroom, you can get ~100 dB rejection at SMPS
frequencies.

You can put a shunt regulator on the cap multiplier to get better load
regulation, e.g. by making it run exactly 2 volts below the input
supply. (You obviously have to filter the thing you're tracking, as well.

While it doesn't work at your power level, one of my favourite
approaches is to use some random laptop power brick followed by 150-kHz
Simple Switchers with toroidal inductors and cap multipliers. Easy,
cheapish, very quiet, no messing around with mains voltages.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

Phil Allison

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Jun 14, 2015, 7:43:54 AM6/14/15

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Trevor Wilson wrote:
>
> I'm looking for a cheap and cheerful bench power supply. Here are the
> desired specs:
>
> 50-0-50 Volts, variable.
> 0-3 Amps, variable.
> Tracking
>
> Ideally, I would like:
>
> 0-5 Amps
> Linear rather than SMPS
> 230/240VAC

** All you need is one of these:

http://product-images.highwire.com/5569873/7432-6.jpg

plus a couple of 1.5V cells.

Gives you a dual tracking supply of 0 to +60V and -60V with single knob control and heaps of current available.

Hint: you switch the amp to "bridge" first.

... Phil

Trevor Wilson

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Jun 14, 2015, 3:58:43 PM6/14/15

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**Nice idea, except I require variable current limiting as well. I
wanted to avoid a DIY exercise. In any case, I've pretty much decided
that a 30-0-30 @ 5A supply will do for the present time. 200 Bucks from
Rockby.

Gareth Magennis

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Jun 14, 2015, 5:32:24 PM6/14/15

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"Phil Allison" wrote in message
news:bd937183-cf4f-42fc...@googlegroups.com...

I had a very painful learning experience with one of these amps, in my very
early days of repairing stuff.

I'd repaired it, tested fine on the bench. Then reassembled it, stupidly
without re-testing it.

Turns out I'd used a screw somewhere near the mains switch that was slightly
too long.
Caused a short, caused both outputs to become DC.

Gave it back to the customer, he connected it to a pair of these:
http://spurwinkproductions.com/Edit%20A%20pictures/813C_1.jpg

Fried all 4 cones.

Since then, nothing ever leaves my workshop without a final test, fully
assembled, ready to go.

Gareth.

Phil Allison

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Jun 14, 2015, 11:03:08 PM6/14/15

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Gareth Magennis wrote:

>
> Since then, nothing ever leaves my workshop without a final test, fully
> assembled, ready to go.
>

** Had a customer once who decided it was perfectly OK to bring just the chassis from his combo amp in for service, with the valves removed and packed separately. He wanted it back that way too.

He was not a customer for long.

Final testing is when you often find new, unreported faults and any errors made during servicing.

... Phil

Trevor Wilson

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Jun 14, 2015, 11:16:26 PM6/14/15

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**Indeed. It is crucial to any decent service job. For any decent
product which hits my bench, it is subject to significant under-load
testing, to reasonable operating temps, plus basic performance tests to
verify operation. For some amps, that can mean several hours of testing.
Particularly those with several tens of kg of heat sinking. Even the
cheapest, crappiest amp that lands on my bench is tested for basic
performance before leaving. Anything less can be a costly mistake.

Nothing worse than a customer who brings in a box full of parts, asking
for me to fix it.

gregz

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Jun 15, 2015, 12:34:28 AM6/15/15

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Got to remember that..

Greg

Phil Allison

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Jun 15, 2015, 2:22:26 AM6/15/15

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GS wrote:

>
> > ** All you need is one of these:
> >
> > http://product-images.highwire.com/5569873/7432-6.jpg
> >
> > plus a couple of 1.5V cells.
> >
> > Gives you a dual tracking supply of 0 to +60V and -60V with single knob
> > control and heaps of current available.
> >
> > Hint: you switch the amp to "bridge" first.
> >
>
>

> Got to remember that..

** You could use the same idea with most dual channel power amps, long as you restore full gain at DC by removing input and feedback loop electros.

... Phil

gghe...@gmail.com

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Jun 15, 2015, 2:26:44 PM6/15/15

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On Thursday, June 11, 2015 at 12:00:30 AM UTC-4, Trevor Wilson wrote:

> I'm looking for a cheap and cheerful bench power supply. Here are the
> desired specs:
>
> 50-0-50 Volts, variable.
> 0-3 Amps, variable.
> Tracking
>
> Ideally, I would like:
>
> 0-5 Amps
> Linear rather than SMPS
> 230/240VAC
>
> The last three are not deal-breakers though. I've seen a few on eBay,
> but am not certain about quality. Like this:
>
> http://www.ebay.com.au/itm/Dr-Meter-HY5005E-2-SWITCHING-DUAL-DC-POWER-SUPPLY-50V-5A-Variable-/221422197471?pt=LH_DefaultDomain_0&hash=item338dca9adf

I think there is one place in China making all those and re-branding them.

We buy them from Mastek.

http://www.mastechpowersupply.com/

The ones we get now say Volteq on the label.
George H.