POWER DESIGNS PRECISION POWER SUPPLIES

[robrenz]

Im pretty happy.  After over a year of wanting another PD PSU I finally got a 2020B;
http://www.ebay.com/itm/Power-Designs-2020B-Variable-Power-Supply-Precision-DC-Calibrator-2AMP-20V-/221195966773?ssPageName=ADME:L:OC:US:3160

You should be happy, these are things of beauty 

[robrenz]

@ c457p

How are you accessing the need for resistor trims? Measuring the individual resistors or extracting which resistors are contributing to a voltage error from the rather complex switching matrix? (which I have not spent the time to understand yet  )

Thanks for any help.

[SeanB]

Plenty of nice ones, but the shipping......... is not nice.

[c4757p]

When I noticed a couple settings were out more than I'd like, I just looked at the switch contacts to see which resistors were involved, disconnected them and measured. Sheer dumb luck allowed me to be correct the first time twice in a row 

[c4757p]

Plenty of nice ones, but the shipping......... is not nice.

Yeah, shipping to South Africa doesn't sound fun. It's not bad to get them across the U.S.

[terabyte]

Im pretty happy.  After over a year of wanting another PD PSU I finally got a 2020B;
http://www.ebay.com/itm/Power-Designs-2020B-Variable-Power-Supply-Precision-DC-Calibrator-2AMP-20V-/221195966773?ssPageName=ADME:L:OC:US:3160

You should be happy, these are things of beauty 

Is there anything I should do when I get it?

[robrenz]

Yes,  read thru this thread from the beginning.   I am serious, there is a lot of good info from lots of people in here.

[c4757p]

Is there anything I should do when I get it?

I will contribute a suggestion that is not specific to this power supply, but still, would have bit me in the ass with mine if I forgot. This applies to all of this old equipment, as it has had many years to break and be fixed by people of significantly varying capability. Don't turn it on, take it apart - check for idiotic, bodgy "repairs" that may have fallen apart over time and may cause trouble. The jackass who had mine before me couldn't even replace a neon indicator without allowing mains potential to short to the chassis - looks like the joint was loosely covered and came undone during shipping.

[terabyte]

Ok thanks guys.  This thread was just a little overwhelming to read the entire thing.

[saturation]

Try statistical summarizers, they tend to get a good executive summary even with technical information; it uses pattern matching so the language or topic is not material.  Try  and see.  Its one of the best features of Microsoft Word that I know most people don't know exists, its been there since the beginning.

There are similar ones online.  To summarize an eevblog page:

Hit print icon on the top of each forum topic, it will create a URL:

https://www.eevblog.com/forum/testgear/looking-for-goodinexpensive-bench-power-supply/?action=printpage

You can print it to read or port it for reading later, like a textbook.

To get an executive summary go to say, here:

http://www.tools4noobs.com/summarize/

Plug in the print output URL on the address and enjoy the bullet items.

You can play with the summarizer options when you get comfortable with what it does.

Ok thanks guys.  This thread was just a little overwhelming to read the entire thing.

[don.r]

Has anyone tried to modify these power supplies? I see that the 2020B uses a fairly old and obsolete op amp as the voltage control amp (uA798HC) which is rather slow.

[andyb]

I've got one for sale over in the Buy / Sell area

https://www.eevblog.com/forum/buysellwanted/fs-power-designs-pd-2005-$50/

[don.r]

I purchased a 2020B the other day. It appears to work fairly well if a little out of cal. Upon looking inside, I notice that the LM399 has a small scorch mark on it. Is this common? I haven't tested the unit for drift yet but I will shortly.

EDIT: doesn't drift much over a few hours.

[SeanB]

LM399's tend to run at 70C, so it will look a little toasty when powered up for a few years.

[don.r]

Thanks for the reply. It seems to be working well and everything is stable so I'll leave it for now but may order a new LM399 in the future "just in case". I see they are currently running around $12-$14 on ebay.. about the same as the DK price.

[SLJ]

Picked this one up at a swap meet last week for $20.  0-50 V/.5 A
I'm happy.

[saturation]

It looks to be in fine shape and has all original knobs  .  I presume its Vout is factory stable perfect 

[robrenz]

Nice one SLJ

I just bought a 6050A from the buy sell on this fourm for $75.00 including shipping.

@ saturation  I think we are tie now

[SLJ]

It looks to be in fine shape and has all original knobs  .  I presume its Vout is factory stable perfect 

Stable, no AC ripple to speak of, and the meter is accurate. 

[robrenz]

Fully functional thing of beauty.  The control amplifier picks from 4 different rectified voltages with transistors/diodes to keep the power dissipation low (trademarked "UNIPLY"). No relay clicking in this one.  Bought a real manual from manuals plus for $25.00 (could not find a pdf anywhere) I especially like the fact that the form factor is the same as the precision supplies.

[manticore00]

My wife's going to kill me but I caught this bug too after reading through this thread and I picked up a 6050A from ebay for less than $70, including shipping. I don't really need it but the quality and beauty seduced me. Trying as hard as I can to resist the call of the Tek 7000 series scopes...

Am I the only one who wishes that some company would match the aesthetic beauty of older equipment with the features and functionality of modern ones?

[robrenz]

As you can tell, you are not alone

[saturation]

Amen,  but on those low noise PD supplies, you'd be hard pressed to find an equal in any era, from the past to today not just the look, but the function.

https://www.eevblog.com/forum/chat/what-is-a-good-power-supply/

https://www.eevblog.com/forum/testgear/looking-for-goodinexpensive-bench-power-supply/msg103401/#msg103401

Some recaps of their history.   

Thus, its worth owning, it gives you some of the quality of a precision source,  even in PD's more 'ordinary' bench PSU.  Overall, the quietness of their supplies are closer to an ideal PSU, i.e., a variable 'battery', than most PSU made today, and the precision types are only bested by a more exotic device that costs 100X more, granted the new ones also do more.

http://www.home.agilent.com/en/pd-2149890-pn-B2961A/65-digit-low-noise-power-source?nid=-33090.1035018&cc=US&lc=eng

But if you are so inclined, your small lab has the capacity to do a level of low noise work  , heretofore reserved to only professional or far better financed labs.

Jim Williams had some and I'm sure he'd agree if he were still around.

My wife's going to kill me but I caught this bug too after reading through this thread..
Am I the only one who wishes that some company would match the aesthetic beauty of older equipment with the features and functionality of modern ones?

As you can tell, you are not alone

[don.r]

So I just received a beautiful Keithley 196 61/2 digit dmm and thought I would put my 2020B through its paces. While working through the voltages I noticed that the 10v and 20v ranges where about 100mv out of sync. I could cal either range to within 20uV but then the other range would be out by 100mV. I checked the 10K 3W precision power resistor that the range switch affects and found it to be 10.02K (10.01773K on 4 wire  O0 ). So that is not 0.01%... no where near. Using a resistance box I found that paralleling 4.7MOhm (how convenient!) would bring me close enough to within 50uV on either range. Looks like these older power resistors drift with time (use?), just something to look out for.

[SLJ]

My wife's going to kill me but I caught this bug too after reading through this thread and I picked up a 6050A from ebay for less than $70, including shipping. I don't really need it but the quality and beauty seduced me. Trying as hard as I can to resist the call of the Tek 7000 series scopes...

If she kills you can I have yours?