POWER DESIGNS PRECISION POWER SUPPLIES

[pelud]

OK, here's the bottom side of the 5020, including the LM399 reference:

[bitseeker]

Cool. That supply should clean up nicely. For the permanent marker on the front panel, give a melamine sponge (a.k.a., Magic Eraser) a try. Since the aluminum panel has a clear coat on it, you might want to test it a bit in the corner or somewhere less conspicuous to verify that it isn't too abrasive. If it does dull the clear coat, you can probably bring it back with an auto clear coat polish.

[PedroDaGr8]

Cool. That supply should clean up nicely. For the permanent marker on the front panel, give a melamine sponge (a.k.a., Magic Eraser) a try. Since the aluminum panel has a clear coat on it, you might want to test it a bit in the corner or somewhere less conspicuous to verify that it isn't too abrasive. If it does dull the clear coat, you can probably bring it back with an auto clear coat polish.

Before using an abrasive I would just use methanol (wood alcohol). It usually does a great job of removing sharpie, though if left on certain materials for too long the sharpie can seep in and then your only solution is an abrasive. Plus most (but not all) clear coat finishes are stable in methanol.

[bitseeker]

Ah. Thanks for the tip, Pedro!

[rsjsouza]

Cool. That supply should clean up nicely. For the permanent marker on the front panel, give a melamine sponge (a.k.a., Magic Eraser) a try. Since the aluminum panel has a clear coat on it, you might want to test it a bit in the corner or somewhere less conspicuous to verify that it isn't too abrasive. If it does dull the clear coat, you can probably bring it back with an auto clear coat polish.

Before using an abrasive I would just use methanol (wood alcohol). It usually does a great job of removing sharpie, though if left on certain materials for too long the sharpie can seep in and then your only solution is an abrasive. Plus most (but not all) clear coat finishes are stable in methanol.

Pedro, I always had the impression methanol's vapors were a neurotoxic substance. However, given you are the chemist, perhaps my fears are unwarranted...

[PedroDaGr8]

Cool. That supply should clean up nicely. For the permanent marker on the front panel, give a melamine sponge (a.k.a., Magic Eraser) a try. Since the aluminum panel has a clear coat on it, you might want to test it a bit in the corner or somewhere less conspicuous to verify that it isn't too abrasive. If it does dull the clear coat, you can probably bring it back with an auto clear coat polish.

Before using an abrasive I would just use methanol (wood alcohol). It usually does a great job of removing sharpie, though if left on certain materials for too long the sharpie can seep in and then your only solution is an abrasive. Plus most (but not all) clear coat finishes are stable in methanol.

Pedro, I always had the impression methanol's vapors were a neurotoxic substance. However, given you are the chemist, perhaps my fears are unwarranted...

methanol isn't that bad from a vapor standpoint. In general as far a toxic substances go, it's pretty benign. Your body naturally produces methanol as a by product of certain chemical reactions, similarly you actually ingest methanol when you eat fruits and veggies. As a result your body has ways of removing it and dealing with it. The NIOSH limits are in the hundreds of mg/m3, making this a relatively benign material. For sure, it, like any toxic substance, should be used in a will ventilated area but it's not something to be afraid of. Usually, I apply it to a paper towel or squirt it with a squirt bottle. For us chemists, we usually keep three squirt bottles on hand. Chloroform, methanol or acetone, and toluene. The methanol bottle is most commonly used for removing permament marker.

[rsjsouza]

Wow, thanks a bunch Pedro. A few weeks ago I had to remove some permanent ink from the top cover of a Keithley 191 and I really wish I knew that - perhaps it would have saved me to waste a lot of "elbow grease". Although Isopropyl alcohol was not terribly bad, as it loosened the ink enough so I could scratch it out somewhat easily with a sewing needle (needed to get into those crevices of the ABS plastic cover)

[Vgkid]

Is it just me, or does R74 look toasty.

[bitseeker]

It's not just you. It seemed a bit crispy on the outside to me, too. It's also interesting that they drilled out the circuit board below the smaller wire-wound resistors. It'd be interesting to get some temps after the supply has been running under load for a while.

[bitseeker]

Here's one I haven't seen before: Model 605 0-6VDC, 0-500mA. Looks like it has their custom oven like the 2005 models. The rear panel is like Swiss cheese.

Someone buy it so it stops tempting me.

http://www.ebay.com/itm/291742748367

Front:


Top:


Rear:

[vindoline]

Here's one I haven't seen before: Model 605 0-6VDC, 0-500mA. Looks like it has their custom oven like the 2005 models. The rear panel is like Swiss cheese.

Someone buy it so it stops tempting me.

http://www.ebay.com/itm/291742748367.

Very cool! I've never seen this model before

[bitseeker]

Looks like someone bought it. Anyone here?

[Ampere]

Looks like someone bought it. Anyone here?

It was me. I've been trying to work with only a single power supply and I've gotten tired of having to include so many regulator ICs even for simple circuits. It'll be nice to have a proper second supply. Especially one that's so much more precise than my current one.

I hope I didn't steal it out from under your nose, but you did say that you wanted someone to buy it. 

[bitseeker]

Hi Ampere! Congrats on joining the PD Precision club. I'm glad someone here got it. Yes, you saved me since your offer was higher.

I've never seen the 605 before, so hopefully you'll post teardown photos of it when you get it.

[Ampere]

My Model 605 arrived in the mail today. I turned it on instead of taking it apart right away (big mistake) and found that it was off by over 50mV on nearly every setting.  Even 0V!

Then I did a cursory teardown (Link) and I think it's pretty obvious what's wrong. Most of the large electrolytics have completely failed so of course it's not going to operate within spec.

I don't have anything like the 100uF 80V on hand except for two salvaged "Jay'Long" 680uF 200V caps, but I wouldn't dare put these monstrosities in what is otherwise quite a nice design. I'll just order some. Serves me right for not keeping enough caps on hand. 

[nanofrog]

I don't have anything like the 100uF 80V on hand except for two salvaged "Jay'Long" 680uF 200V caps, but I wouldn't dare put these monstrosities in what is otherwise quite a nice design. I'll just order some. Serves me right for not keeping enough caps on hand. 

Meh. It helps keep your rarely used parts inventory under control, which is a good thing IMHO.   

[bitseeker]

Cool little supply. Thanks for the teardown photos. Big cans. Some crusty caps. A little dusty, but should be pretty nice once you've gone through it.

[pelud]

I finally got some time today to test out the Power Designs 5020.  Unfortunately, it doesn't work  

The original seller stated that there was no output when he first attempted to test it, but then it started working. Quote from seller: "When I received this power supply, it powered on, but there was no output. Both the internal, and the rear mounted fuses checked out, and after I checked them, the power supply began working properly, as shown in the photos, so there may be a loose connection somewhere."

I should have known better to fire the thing up without checking the caps, etc, but I was getting too impatient to wait.  I heard a bit of a "frying" noise when first turning it on, although nothing smells or looks abnormal.  The voltage reading on the front panel meter never moved, but the output reads -46V on my DMM.

[bitseeker]

Hi John,

Sorry to hear about the sizzling. If you look at the bottom board, the power resistor R74 already looked pretty crispy in your teardown photos. Check the rectifier diodes (C29 and up) and the filter caps (C32, C33). One or more might be shorted.

I don't have schematics handy for this supply, but those are my initial impressions. Looking forward to hear what you discover. I may get a 5020 one of these days.

[timb]

Here's one I haven't seen before: Model 605 0-6VDC, 0-500mA. Looks like it has their custom oven like the 2005 models. The rear panel is like Swiss cheese.

Someone buy it so it stops tempting me.

http://www.ebay.com/itm/291742748367

Front:


Top:


Rear:

Somehow I lost track of this thread, so I totally missed this! I picked one of these up on eBay about a year ago, but it's still sitting in a box awaiting restoration. Mine powers up, but the oven never goes off, so I think the thermostat is bad.

That's a very common problem with all these ovenized PD supplies and a big disadvantage to keeping the oven powered even when the supply is turned off: The thermostats use a bimetallic disc which wears out after a few hundred thousand cycles.

The thermostat module is actually soldered to the bottom of the oven's inner can (under the socket). It's of a size and shape that appears to no longer be made and I've been unable to locate a suitable replacement.

It's such a common problem, that I've actually designed a fairly simple, yet accurate oven controller as a replacement. It's 100% solid state and keeps the oven within 0.5C of the set point. Originally I intended to use a relay, but opted for a little Triac in a SOIC package instead (no sense replacing a mechanical switch with another mechanical switch).

I need to finish laying out the board, but once I do I'll have a batch made and do some final tests with my own supplies. If everything works out, I'll offer up retrofit kits if anyone is interested. It should be rather simple to swap over to my controller.

[bitseeker]

That retrofit kit sounds great, Tim. I've avoided the older models because of that oven and ended up getting a 2010 instead.

[Ampere]

Sorry for keeping you all waiting so long for an update. I powered on the 605 after switching out the caps (all but the very largest which seemed OK) and the supply still does not work. The voltages all wrong. When set to 0V, I'm reading -4.64mV. When set to 1V, I'm measuring 990.7mV. Etc. I don't think it is the temperature control problem mentioned above because the voltages do not appear to depend on whether the oven is currently on or off. Is it possible that the reference itself could have gone bad or drifted over time?

[bitseeker]

It doesn't seem very far off: 9.3 mV out of 1 V is 0.9%. It could just need adjusting. However, blindly adjusting the output could mask problems. Check it at several more voltage levels throughout the entire range. See if it's off by a similar percentage. If it is, then it probably just needs adjusting. It is old, after all.

[Ampere]

I allowed more time for the voltage to settle and I'm getting the results shown below. They aren't the same results I was getting before for 0V and 100mV, but maybe it took a few heating cycles to really settle because the new results I got last night and the ones I'm getting now are very, very close.

Is it normal for the lower ranges to be off by so much more than the higher ones? If that's normal then I wouldn't mind giving it a tweak.  My best meter is only 0.1%(+2) accurate, but I'd be happy if I could get the supply close to that.

[Vgkid]

That is not unexpected, the lower ranges use less accurate voltage setting resistors.
Also: what is the accuracy of your meter below a volt.