POWER DESIGNS PRECISION POWER SUPPLIES

[GK]

Looking at those photos posted by SLJ I just assumed remote sensing wasn't a feature as there are no appropriate/bridgeable binding posts on the front panel besides the output binding posts for the purpose.

[robrenz]

No problem, your forgiven, as long as you have a glass of coolaid on us

[don.r]

Most of these older supplies put them on a barrier strip on the back.

[JBeale]

I am checking out an old Power Designs Model 2005A which has been sitting in a garage for a long time. I don't have anything to check it with better than a Keithley 196 DMM (from ebay, and 4 years out of calibration).  The 2005A seems to mostly work.  After warmup, the OVEN lamp flickers sometimes as it probably should, and the indicated voltage output drifts less than 20 ppm in one day.  However, pressing on or slightly jiggling any of the four rotary voltage selectors shows some jumpiness in the output, so clearly there are dirty contacts. I haven't taken it apart yet. Are these contacts copper, silver, gold, something else? Is a spray with contact cleaner likely to help, or will a full disassembly and/or replacement be the only cure?  I have seen Caig DeoxIT recommended, but they seem to sell many different varieties for different contact metals and situations.



Update: ironically, *as I was writing this post* the Keithley's LED display blinked out (it had been working without issue for months). The internal analog +/- 15V power rails are still ok... anyway, a problem for another post.

[robrenz]

I suggest compressed air first if you have it to remove all dust that will blow off. Then a thourough wash with a general electronic cleaner to get the general gunk off the switch assemblies and the detents.  The detents will probably have caked old grease in the ball pockets. Then apply deoxit D100L to all the contact fingers and thoroughly cycle the switches. Re lube all the places where the switch shaft engages other parts and grease the detent assemblies. I personally like wash the D100L off and then lubricate with Deoxit G100L.

some links from this thread here

[uoficowboy]

OK - since this is the Power Designs mecca thread...

I have a TW5005W. Lovely supply. Mine needed a couple electrolytics replaced when I received it but has otherwise aged very gracefully.

Only thing is that I am kind of a stickler for cleanliness. I removed all the stickers from it. Got rid of all the adhesive gunk from beneath the stickers. But unfortunately, some of the stickers had been on there... a long time. So the metal front panel (Aluminum I think?), has yellowed in all places except where the stickers were (oh, and also beneath the knobs). Beneath the stickers and knobs, the color is fine. I noticed a bit of acetone gets rid of the yellowing, but I'm worried that the acetone will remove all the silkscreened labels so I have not pursued that.

Any suggestions for getting rid of the discoloration? Any idea what it is?

Sorry to not talk about their precision supplies. I have one of those too - a 5020 - but it hasn't needed any work and also still looks pretty.

[robrenz]

Have you tried magic sponges?

[uoficowboy]

Have you tried magic sponges?

No but I don't trust those things - they're pretty much just normal sponges mixed with sand and chemicals. I think they'd take off the silkscreen as well as the yellowing.

[don.r]

Have you tried magic sponges?

No but I don't trust those things - they're pretty much just normal sponges mixed with sand and chemicals. I think they'd take off the silkscreen as well as the yellowing.

Usually, they are made from melamine foam.

It is also the component of Magic Eraser and similar cleaning products.

As long as the surface you are cleaning is not softer than melamine, it will not scratch. Silkscreen may be an issue.

[dave3533]

When you guys are cleaning the decade voltage knobs, are you removing them from the supply or just cleaning them in place?  If you are removing them, how difficult is it?

Thanks!
 

[robrenz]

I cleaned mine in place.

[don.r]

In place. QTip and IPA.

[c4757p]

If you are removing them, how difficult is it?

Don't even think about it.

[dave3533]

Don't even think about it.

I figured that was probably the case 

I purchased this 5020 on ebay and it was in poor shape initially.  The circuit board visible from the top of the unit was coated in black dust.  I've used denatured alcohol to clean most of the grime out (think I have about 3 hours of cleaning into the top circuit board  ). 

I still haven't figured out the best way to clean the front aluminum, any suggestions?





I also noticed that the circled component below seems to have a "loose" top, ie it will wiggle and slightly rotate.  I've essentially left it alone for now to prevent damage, as the supply seems to work well regardless.  I'll look up the component after I finish cleaning.



Once I finish cleaning it I'll put it through its paces

[c4757p]

I also noticed that the circled component below seems to have a "loose" top, ie it will wiggle and slightly rotate.  I've essentially left it alone for now to prevent damage, as the supply seems to work well regardless.  I'll look up the component after I finish cleaning.

That's no inductor, that's the voltage reference (LM399 is a classic precision oven-stabilized reference). It's supposed to be loose like that.

It sure has evolved from the massive red can oven in the earlier models! And woo! PCB! Mine's point-to-point on turrets stuck in a piece of copperless FR4-ish material.

[SLJ]

I cleaned the front of mine with rubbing alcohol.  Put it on with a swab and let it soak into the stickers and then used a wide plastic alignment tool to scrape most of the paper and glue off.  then used more and wiping with a paper towel until they were clean.  Did not seem to bother the silk screened markings.

[ddavidebor]

Naaa alcool don't work very well.

You should use a degreaser (for the kitchen, NOT a solvent based ones)

Il you want it like new you must remove everything from the front panel and clean it separately.

Next, you should use alcool to remove all the trace of the degreaser especially from glass surface.

Here i use chanteclair, is a  degrasser. It's so good that i buy it in 5L bottle.

[ElektroQuark]

Some degreasers have NaOH as main active ingredient. NaOH eats aluminium, so beware, they can damage the panel finish.

[robrenz]

Naaa alcool don't work very well.

You should use a degreaser (for the kitchen, NOT a solvent based ones)

Il you want it like new you must remove everything from the front panel and clean it separately.

Next, you should use alcool to remove all the trace of the degreaser especially from glass surface.

Here i use chanteclair, is a  degrasser. It's so good that i buy it in 5L bottle.

Why would you contradict a forum member that has cleaned more equipment than you have even seen? 

[SLJ]

Before/After


Remember to let the alcohol sit on the paper stickers to soften them.  Still watch out for any screened printing. It did OK with both my PD supplies but depending on manufacturer it could still do damage to the print.  Again, something soft plastic helps scrape off the goop without scratching the panel.

Actually sticker and label glue is not usually as bad as smoke residue.  Some of the early test equipment is so bad the panels have to be removed and soaked.  Bakelite panels and cases can be cleaned and polished using mag wheel cleaner you get at an auto supply but it removes any printing.  I would not use it on brushed metal panels though.

[robrenz]

I have found Toluene and Xylene especially effective on sticker goo.  "Goof off" and "Goo gone" are two that are readily available in the US with same or similar active ingredients. These will usualy totaly liquify the adhesives right through the stickers if the stickers are paper/pourous. If the stickers are non pourous then you need to keep a "wet front" on one edge as you gradualy peel the sticker up.  As with most things the magic sponges will enhance the cleaning action.

[nukie]

LM399 in a power supply!!!

[uoficowboy]

Has anybody tried taking apart the rotary switches? I'd like to clean the contacts on the other right knob on my 5020. They are showing their age a bit...

[SLJ]

Has anybody tried taking apart the rotary switches? I'd like to clean the contacts on the other right knob on my 5020. They are showing their age a bit...

See page 16.

[uoficowboy]

Has anybody tried taking apart the rotary switches? I'd like to clean the contacts on the other right knob on my 5020. They are showing their age a bit...

See page 16.

Nobody seems to have tried, hence my question.

On a side note - anybody have a *clean* scan of the schematics for the 2020 or 5020? The only ones out there seem to be pretty much unreadable.