Author Topic: POWER DESIGNS PRECISION POWER SUPPLIES  (Read 265246 times)

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Offline timb

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #375 on: November 03, 2014, 01:26:03 pm »

The LM399 has built-in heater control, right? The data sheet doesn't mention, is it static off/on control, or simply a series of transistors that operate linearly in response to temperature? (I know current can vary on them, so I assume the later. This isn't in reference to anything specific, just a curiosity I've always had with the 399.)

It has a pass transistor and heater control circuit which operate linearly.  The power drawn by the heater circuit is inversely proportional to external temperature as expected and drops to zero at about 85C.  At 25C, it draws about 300 milliwatts.  Operating voltage is from 9 to 40 volts.

The heater and zener allow for roughly an improvement of 5 to 20 times over a precision bandgap reference.

Cool, that's about what I thought. I figured it might be neat to stick a simple shunt resistor on the heater power input (or output) hooked to a comparator to activate the "Oven" lamp on the 2005A. (Replaced with an LED, obviously.)

It would help keep things original looking too.


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Offline MarkPalmer

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #376 on: November 03, 2014, 02:21:57 pm »
I’m the fool who bought the latest 5020 that was sold on E-Bay, if only just to have some fun with it and add it to my PD collection so to say, which are all power supplies in regular use.  Not too badly priced at $129.00.  I could have waited for one to come along cheaper, but this is the exact PD precision model I have wanted.  Claimed to be, “guaranteed working.”  Yeah, I know darn well how that often goes!  Cosmetically the front doesn’t look like anything that won’t clean up fairly decent, and I’ll strip the old paint and give the outer cabinet a fresh spray of Krylon Bahama Sea blue.  This was one of the last precision models made by the “real” Power Designs company looking to have been designed around 1978 or so, and it uses the LM399 reference. 

-Mark-
 
 

Offline timb

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #377 on: November 03, 2014, 11:36:03 pm »
You know, one issue I'm having is finding useful data on some of these old parts, like the diodes on the 2005A oven board. Man, I'd kill for some old data books!


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Offline motocoder

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #378 on: November 03, 2014, 11:42:44 pm »

The LM399 has built-in heater control, right? The data sheet doesn't mention, is it static off/on control, or simply a series of transistors that operate linearly in response to temperature? (I know current can vary on them, so I assume the later. This isn't in reference to anything specific, just a curiosity I've always had with the 399.)

It has a pass transistor and heater control circuit which operate linearly.  The power drawn by the heater circuit is inversely proportional to external temperature as expected and drops to zero at about 85C.  At 25C, it draws about 300 milliwatts.  Operating voltage is from 9 to 40 volts.

The heater and zener allow for roughly an improvement of 5 to 20 times over a precision bandgap reference.

Cool, that's about what I thought. I figured it might be neat to stick a simple shunt resistor on the heater power input (or output) hooked to a comparator to activate the "Oven" lamp on the 2005A. (Replaced with an LED, obviously.)

It would help keep things original looking too.


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Or you could use the LTZ1000, which has an internal heater but external heater control. But actually, I think that LM399 heats up so quickly that it doesn't make sense to even have an oven light. These parts don't have to heat up a giant mass since it's just a heater built into the substrate of the chip.
 

Offline timb

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POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #379 on: November 04, 2014, 02:04:07 pm »

The LM399 has built-in heater control, right? The data sheet doesn't mention, is it static off/on control, or simply a series of transistors that operate linearly in response to temperature? (I know current can vary on them, so I assume the later. This isn't in reference to anything specific, just a curiosity I've always had with the 399.)

It has a pass transistor and heater control circuit which operate linearly.  The power drawn by the heater circuit is inversely proportional to external temperature as expected and drops to zero at about 85C.  At 25C, it draws about 300 milliwatts.  Operating voltage is from 9 to 40 volts.

The heater and zener allow for roughly an improvement of 5 to 20 times over a precision bandgap reference.

Cool, that's about what I thought. I figured it might be neat to stick a simple shunt resistor on the heater power input (or output) hooked to a comparator to activate the "Oven" lamp on the 2005A. (Replaced with an LED, obviously.)

It would help keep things original looking too.


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Or you could use the LTZ1000, which has an internal heater but external heater control. But actually, I think that LM399 heats up so quickly that it doesn't make sense to even have an oven light. These parts don't have to heat up a giant mass since it's just a heater built into the substrate of the chip.

Yeah, I was thinking about that. I measured one of my LM399H's current draw last night and it's pretty variable, so in the end I may just PWM an LED to reflect that for the oven light. This is all putting the cart before the horse anyway, just something fun I thought of.

Anyway, I built up the existing oven board into my basic simulator last night (iCircuit), just to get a feel for it and make sure I understand how everything works. I'll provide the file if anyone is interested. (I'm working on the entire 2005A as well; just breaking it down into sub-circuits). This isn't anywhere near as complex as LT Spice, but seeing the current actively flow is an invaluable reverse engineering aid I've found!




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Offline motocoder

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #380 on: November 04, 2014, 03:55:21 pm »
that is great. Please share the 2005a circuit when you are done.
 

Offline MarkPalmer

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #381 on: November 04, 2014, 04:25:30 pm »
You can compare the schematics of the supplies using the older style reference to those using the LM399 and see that in the late 70's PD took the time to more or less re-engineer the whole thing when they changed the voltage reference to the to LM.  That may or may not be the path you end up taking if attempting to convert to a more modern voltage reference and end up with a supply that works the way it should. 

-Mark-
 

Offline timb

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #382 on: November 04, 2014, 08:46:52 pm »
Yeah, I've got a 2020B as well that uses the 399. I suspect part of the redesign was to use more modern components and techniques as well, as some of the parts in the 2005A series were EOL by the mid-70's! Luckily the LM399's nominal voltage falls in line with that of CR9 on the 2005A ref, so it might be doable.


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Offline timb

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #383 on: November 05, 2014, 12:04:13 pm »
I picked up some paint to redo my cases today. It's Rustoleum "Lagoon".

Here's a test spot with normal house lighting:



Now under white LED lighting:



It doesn't look anywhere near that blue in person. The other option was Krylon's "Jade" but I thought it would be too green.

Personally, I kind of dig the color; sets it apart from Tektronix gear, so I might go with it, even for the units I resell.

In other news, that new OpAmp will be here today, so I need to get the front back on the 2020B!



I took it off to really clean and test the switches and pots. I tested the switch bank, with a four wire lead hooked up, I went through the entire range from least significant decade up. With the switches set to 9.99[10] I got 10.00001k on my 6.5 digit HP '57A. Not a signal damn resistor was out. After 35 years!

I also took the current pot/switch and vernier apart, scrubbed them out good, relubed with WD-40's White Lithium Grease (that stuff is amazing; you spray it and it "drys" into a normal film of lithium grease), then used DeOXIT Shield to protect the wiper contacts.

The switch portion of the current pot got sprayed with WD-40 Silicone Lubricant and the contacts cleaned and shielded with DeOXIT.



What do you guys think for the moving parts of the switch banks, lithium grease or silicone lubricant?


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Offline motocoder

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #384 on: November 05, 2014, 01:44:49 pm »
Paint looks good.

I was told to use lightweight grease for the bearings/moving parts. I ended up using some firearms lubricant that I had. It is sort of like a slightly runny grease.

BTW - how did you ship that nichrome wire? I am sort of surprised it isn't here yet.
 

Offline MarkPalmer

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #385 on: November 05, 2014, 03:11:43 pm »
The paint looks nice, sometimes a little change is good.  Krylon Bahama Sea is about the closest you can find to "Tektronix" blue at the store, but not everyone who sells Krylon carries the color. 

With precision instrumentation contacts I clean them with anything I know won't leave any residue film, CRC QD cleaner is pretty good as is pure isopropyl alcohol.  Sometimes heavily built up oxides make this hard to do though, and you have to break out something from Caig with a bit of acid in it- just rinse it off really good with IPA after cleaning so that the contacts are dry and film free. 

-Mark-
 
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Offline timb

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #386 on: November 05, 2014, 05:40:43 pm »
Yeah, I clean with 97% Isopropyl. Sometimes I use a bit of Dawn dish soap and a toothbrush first to get rid of grease and oils, then scrub with the Iso, then a final rinse with either 25/75 Iso/Distilled Water or the straight Iso, which speeds drying and doesn't leave water spots!

I use the original DeOXIT for oxidized contacts. Good stuff.


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Offline timb

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #387 on: November 05, 2014, 05:43:16 pm »

Paint looks good.

I was told to use lightweight grease for the bearings/moving parts. I ended up using some firearms lubricant that I had. It is sort of like a slightly runny grease.

BTW - how did you ship that nichrome wire? I am sort of surprised it isn't here yet.

First class, let me know if it's not there today. I'll send another batch Priority I guess.

I should have known better as I've been having massive delays with first class stuff lately. :(


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Online David Hess

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #388 on: November 05, 2014, 06:07:47 pm »
It has a pass transistor and heater control circuit which operate linearly.  The power drawn by the heater circuit is inversely proportional to external temperature as expected and drops to zero at about 85C.  At 25C, it draws about 300 milliwatts.  Operating voltage is from 9 to 40 volts.

Cool, that's about what I thought. I figured it might be neat to stick a simple shunt resistor on the heater power input (or output) hooked to a comparator to activate the "Oven" lamp on the 2005A. (Replaced with an LED, obviously.)

Your PWM idea is good.  What I was thinking is that since the warmup time is pretty short, an operational amplifier differentiator could be used to detect the period of time when the reference temperature has not stabilized making the oven indicator a warming up indicator.
 

Offline Alex Eisenhut

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #389 on: November 05, 2014, 08:06:29 pm »
You know, one issue I'm having is finding useful data on some of these old parts, like the diodes on the 2005A oven board. Man, I'd kill for some old data books!


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EE dep't at a university?
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Offline timb

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #390 on: November 06, 2014, 09:38:43 am »
Hmm, I've got a buddy who's a Virginia Tech alumni, maybe he can find out if they do. I highly doubt it though.

The new OpAmp for my 2020B came in today, yay! Still finishing up the front panel though so haven't tried it yet. I got the vernier and current pots feeling like brand new now.

I've also the power and sense wires that normally go to the banana connector soldered together with a short 2ish inch extension wire, since they were snipped too short when removing the OEM jacks. The plan is to use rung style crimp connectors for power, the original capacitor board for the caps, plus a small wire from where a cap hooks to - and + which will go to the meter switch.

This should be a lot nicer than soldering everything on outright.



That front panel is in pretty bad shape. No matter how much scrubbing and cleaning I do. Eventually I'd like to have a custom one produced, with room for a long dual led bargraph and some HP bubble displays in lieu of a mechanical meter.




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Offline motocoder

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #391 on: November 06, 2014, 11:18:43 am »
sounds like it is all starting to come together.

BTW - no joy on that wire. Can you PM me the address you used so I can make sure there wasn't a typo or something?
 

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #392 on: November 06, 2014, 02:17:26 pm »
It's looking good!  Sometimes Maguar's cleaner wax or even a little toothpaste can help to hide those old sticker shadows on aluminum panels.

The college I work at (Penn State) doesn’t keep much of anything old around as far as literature or equipment, because they don’t teach anything old school in the electrical engineering classes.  You learn the basics in physics classes, and the engineering classes are either what is around now, or what is to be.  A power supply like the Power Designs precision models would garnish little more than snickers, that from most college kids who have no understanding of what it is.  To them, it would be something tossed to the curb because it’s not what they are being taught to use for the development of the next generation of iPad. 

I got my 5020 toy yesterday.  Not too bad, about par for the course, it did power up and work to a fairly good degree on initial test.  I checked all the e-caps and most tested excellent short of the 4 Sprague 1uF 100 volt ones that had ridiculously high ESR and leakage thus will be replaced.   The switch contacts are sketchy as expected also and need a good cleaning.   But even with that, the output voltage would stabilize nicely after about 15 minutes down to the last digit on my 3456A.  So hopefully this one will end up calibrating well after repair and not turn in to one of those continuous science projects. 

-Mark-
 

Offline Alex Eisenhut

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #393 on: November 06, 2014, 03:53:19 pm »
Hmm, I've got a buddy who's a Virginia Tech alumni, maybe he can find out if they do. I highly doubt it though.


I can look at Concordia here, they had 1960s stuff back when I looked for vintage Tek parts info.
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Offline idpromnut

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #394 on: November 06, 2014, 03:56:15 pm »
Hmm, I've got a buddy who's a Virginia Tech alumni, maybe he can find out if they do. I highly doubt it though.


I can look at Concordia here, they had 1960s stuff back when I looked for vintage Tek parts info.

Ha!  A fellow Montrealer! :D
 

Online David Hess

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #395 on: November 06, 2014, 04:27:42 pm »
You know, one issue I'm having is finding useful data on some of these old parts, like the diodes on the 2005A oven board. Man, I'd kill for some old data books!

In the case of the interesting parts, I suspect Power Designs was grading them anyway so the original specifications would be of limited use.  I usually end up reverse engineering the circuit in detail to find out what the specifications needed to be.

If I wanted to work from the part number, I would start is one of the Derivation and Tabulation Associates "D.A.T.A" books.
 

Offline motocoder

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #396 on: November 06, 2014, 05:19:01 pm »
You know, one issue I'm having is finding useful data on some of these old parts, like the diodes on the 2005A oven board. Man, I'd kill for some old data books!

In the case of the interesting parts, I suspect Power Designs was grading them anyway so the original specifications would be of limited use.  I usually end up reverse engineering the circuit in detail to find out what the specifications needed to be.

If I wanted to work from the part number, I would start is one of the Derivation and Tabulation Associates "D.A.T.A" books.

They were definitely grading them. I forget where exactly it says this, but somewhere in the 2005A manual it mentions that the parts were selected from batches for specific qualities (probably transistor Beta).
 

Offline MarkPalmer

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #397 on: November 06, 2014, 05:43:15 pm »
A fellow on the Antique Radio forum said they did their own semiconductor matching in house.  I have seen some Sprague electrolytics in these supplies labeled, "For Power Designs," but I'm not sure what would be so special about them.  I know at least in the HV supplies, they made their own transformers rather than buy them from suppliers. 

-Mark-


 

Online David Hess

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #398 on: November 06, 2014, 07:25:31 pm »
A fellow on the Antique Radio forum said they did their own semiconductor matching in house.  I have seen some Sprague electrolytics in these supplies labeled, "For Power Designs," but I'm not sure what would be so special about them.  I know at least in the HV supplies, they made their own transformers rather than buy them from suppliers.

I wondered about that when looking through their parts lists because almost all of the parts including capacitors have Power Designs listed as the manufacturer.  A similar parts list from Tektronix would list the source of the parts separate from any graded specifications.

I assume besides grading that Power Designs did extensive quality assurance on all of their incoming parts.
 

Offline Alex Eisenhut

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Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Reply #399 on: November 06, 2014, 07:36:06 pm »
Hmm, I've got a buddy who's a Virginia Tech alumni, maybe he can find out if they do. I highly doubt it though.


I can look at Concordia here, they had 1960s stuff back when I looked for vintage Tek parts info.

Ha!  A fellow Montrealer! :D

Yup, there's also McGill, ETS, and maybe UQAM that might have musty old books.
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