EEVblog #649 - Power Designs 2005 PSU Teardown

[EEVblog]

What's inside a 1964 vintage Power Design 2005 Precision Power Supply?
Schematic: http://www.rako.com/Articles/assets_c/2011/05/Power_Designs_Model_2005_Schematic-thumb-512x331-53.gif

[robrenz]

Beauty    The main thread on these PD supplies is HERE.  That is an older version with the flat face meter. The later 2005A units have the edge style meter.

Please do a video with calibration, stability and ripple tests. Put that 34461A charting to work   IIRC you need to adjust zero pot at zero output first then calibrate at 20V output.

Now you need a HP6114A or HP6115A to take the old school up a notch

[BravoV]

Ok, its started, all cheap PDs and 611xA will be gone soon, hurry guys ! 

[gregallenwarner]

Very interesting, Dave! Even if you decide not to try and bring it back into spec, I'd still love to see the output of this thing on the scope, to see if it can still hold its own as far as ripple and stability go!

[Mandelbrot]

Awesome.   I just heard about these things last week from the thread on the forum, and now this video pops up! I would personally love to see a calibration video on this.

I'm also really glad I bought a TW5005W on ebay on Friday instead of waiting! No doubt the market for these will increase after your video.

[FrankBuss]

I think it is easy to bring it back into spec. Depending on the direction of R12, removing R79 should help, so that you can adjust it from 0 to 200 ohm instead 0 to 100 ohm. If it is the other direction, remove R79 and solder 100 ohm in series to R12 (but you should use one of those old carbon resistors ).

That's nice with these old devices. They will still work in 100 years, unlike modern microcontroller controlled devices, where the flash memory will be lost by then.

[warp_foo]

Nice video, Dave! Thanks.

Two things:

1. I already have a PD 2005, so I don't need to worry about the eBay 'eevblog' effect. 
2. Yes, a repair/cal video would be appreciated

m

[dentaku]

The way the front panel is designed makes it look like it's meant to be mounted in a rack.

[Mandelbrot]

The way the front panel is designed makes it look like it's meant to be mounted in a rack.

There was an adapter available for mounting these in a standard 19-inch rack. It is however designed for bench use. Two can be mounted side by side on one of these racks.

There is a manual for the model 2005 here: http://www.ko4bb.com/Manuals/09%29_Misc_Test_Equipment/Power_Designs/Power_Designs_2005_Power_Supply.pdf

[PedroDaGr8]

Ok, its started, all cheap PDs and 611xA will be gone soon, hurry guys ! 

Haha no joke. I just pray he doesn't do a 611x teardown. They are already so damn hard to find. If he was impressed with this design. Imagine him looking at the 611x.

[BravoV]

Haha no joke. I just pray he doesn't do a 611x teardown. They are already so damn hard to find. If he was impressed with this design. Imagine him looking at the 611x.

Actually its not the 611x tear down that I'm worrying about, it is the moment Dave decided to test and demonstrate in the video it's accuracy, stability and regulation under his scope view, and tortured with a "dynamic" load, not just static load.

If that really happened, then we will be in deep trouble finding it. 

[Rigby]

They're only hard to find if you have a budget.

I call my management out every time they say "there just aren't people available with those qualifications."  There are plenty folks with those qualifications, they just ask for wages that match their talents, and that removes them from consideration.

[Vgkid]

I don't think that I will be able to afford one now... I guess I will roll my own then.

[PedroDaGr8]

They're only hard to find if you have a budget.

I call my management out every time they say "there just aren't people available with those qualifications."  There are plenty folks with those qualifications, they just ask for wages that match their talents, and that removes them from consideration.

Of course, as hobbyists most of us have a limited budget. If budget was no option, we would be looking at the modern equivalents at 50x the price. So while you are correct, the budget in this case is implicit. A meter with these specs that fits within our budgets.

[calexanian]

That is a turret board. Very common up until the 70's in high stability or military equipment dating all the way back to the 30's. They are still used in fancy schmancy audio and guitar amplifier circuits because, well, it looks cool! Look closely at the way the wire is wrapped around lugs and notice the sparing use of solder. This is straight out of the military servicing manual. They would even specify the angles of the bends of the wire. Very cool stuff. One day I will post scans of one of those manuals regarding wire wrapped solder lugs, those nifty split turrets, and the eyelet turrets. You can get your bottom dollar those joints are good.

As for the unit being out of spec, are you still as "In Spec" as you were at 18? Most likely not. Couple things come to mind. The electrolytic caps are due for a change, and those carbon resistors are going to drift. You could do the lazy mans job (And in this case its the way I would probably go) and bodge in a resistor to bring the divider string into cal, replace the filter capacitors, and call it a day. I have an E/M scientific supply from about the same time. Not as well made, but it can supply up to 110 VDC at up to 1.2 amps regulated. It has 2 puck style germanium pass transistors on it and groans when you swing the voltage around! Just for kicks I light my office lab with a hundred watt bulb with regulated DC. Its like thousand dollar champagne. Is in no measurable way better, but wasteful and unnecessary, not to mention fun!

[coppice]

Schematics with negative at the top and positive at the bottom were very normal in the 60s. Most designs were very PNP transistor centric in those days, and a PNP oriented schematic looks more like a valve/tube schematic when you put the negative at the top.

It looks like everything in that PSU is silicon. Most designs in 1964 were full of germanium transistors. Many PSUs even had copper oxide rectifiers at that time.

[coppice]

That is a turret board. Very common up until the 70's in high stability or military equipment dating all the way back to the 30's.

I think 1964 was before the introduction of plated through boards. They were certainly not in widespread use then. Turret tag boards are more reliable than a single sided PCB, so it was the most appropriate choice for a product like this supply.

[Dave Turner]

That reminds me of a lot of kit that I picked up at the Army & Navy stores in the 60's when my soldering iron was a lump of copper on a stick heated on the gas stove.

Oh - you wanted a greybeard - it took some time to get the tongue at the right angle!

[EEVblog]

Oh - you wanted a greybeard - it took some time to get the tongue at the right angle!

There's a tongue in there?   

[EEVblog]

As for the unit being out of spec, are you still as "In Spec" as you were at 18? Most likely not. Couple things come to mind. The electrolytic caps are due for a change, and those carbon resistors are going to drift. You could do the lazy mans job (And in this case its the way I would probably go) and bodge in a resistor to bring the divider string into cal, replace the filter capacitors, and call it a day.

Yes, will probably do at least that. But would be nice to hunt down the drifting culprit.

[G7PSK]

I would clean that big wire wound trim pot before doing anything else, the wire and the wipers in them develop a patina over the years and cause the resistance between the wire and wiper to rise.  I have taken them apart in the past and rubbed the wire face with very fine wet and dry along with the wiper.

[SpiderElectronics]

Love it. Nice piece of gear that.
I remember back in 1985 at University learning Electronic Engineering I had to do a section on loom wiring and lacing up just like that power supply. Fantastic, IWOOT!

[Kjelt]

I love those old school wirelooms cablestitching.
I once learnt it 20 years ago from a friend but due to lack of exercise forgot all about it in time.
They are much better then those nowadays plastick tiewraps that stick out and are always in the way.
Found this document online how Nasa does it, time to learn to stitch my knots all over again 

[robrenz]

Since these supplies have very low ripple. It would be interesting to see it measured with a DSA, SA, scope, rms AC meter and see how the measurements correlate between instruments.

[dr.diesel]

That old beauty absolutely deserves a proper referb and cal.  Another vote for making it so, 

[wn1fju]

Just some random thoughts that may or may not already be known.  In my PD2005, the calibration procedure calls for adjusting two pots - a 0V pot and a 20V pot.  However, I was unable to get the 2005 properly adjusted, particularly in the 10 to 20V range.  And that is because the voltage selection switches really only generate intermediate voltages between 0 and 10V; they add an additional 10V (1 ma through a precision 10K resistor) to bring it up to the 10 to 20V range.  If that 10K resistor is off, calibrating it solely at 20V is guaranteed to screw either the 0-10V or 10-20V range, take your pick.  What they really should have done is add a trimmer to the 10K resistor and let you first calibrate it at 10V and then use the trimmer to translate that calibrated range into 10-20V.  And so that is what I did.  Now I am comfortably achieving a maximum voltage error of 0.05% (against the 0.1% spec) with most voltages only off by about 0.02%.  Also, my unit would never achieve the ripple spec.   I hooked up a scope and saw a 1.2 MHz sinewave of several hundred mV.  I was able to eliminate that oscillation by tacking on a small capacitor across Q4, B-C.   Finally, the service manual does have some errata which calls for a few additional caps to be added. 

[HP-ILnerd]

Keep the vintage tech coming, Dave!  It's nice to see all the point-to-point without so much as a single BGA anywhere.

Any chance you could acquire an HP200a?  Bill and Dave's first product would make a splendid episode. 

[corrado33]

That old beauty absolutely deserves a proper referb and cal.  Another vote for making it so, 

Agreed, I'd love to see another video on this lovely bit of old tech! (Plus those types of videos are awesome, albeit most likely frustrating for Dave.)

[williefleete]

That output was out by at least 2.5% at most! if it can't be bought back by tweaking on the pots, either resistors drifted, transistors went leaky or the Zener drifted, if it's the latter (two) and most of the precision (and perhaps not-so precision) resistors check out, he may have to crack open the heater can.

C'mon troubleshoot and repair video

[riconette]

have you seen any whiskers, or otherwise funny/corroded solderpoints?

i wonder - from the video the internals look *so* clean.

[Dr. Frank]

Nice Video, and interesting to see, that in 1964, silicon transistors were very common already.

In the end, the topology of the circuitry is very similar to what Fluke in 1965 (!) designed in the early 332A calibrator,  i.e. an ovenized zener, a stable, inverting OpAmp, a trimmable range resistor, and 4 1/2 decades of wire wound resistors for the sample string. (The 1/2 digit consists of a 10k ww resistor, R45).
The Fluke 332 / 335 instruments are also designed "the other way round", if you study the  "Theory of Operation" in later manuals.

Therefore - no need to turn the schematic of the 2005 PSU upside down, not even in Australia  ...

And that transistor pair Q5 is NOT a current mirror, in this sense, it's simply the front end, i.e. the differential input stage of the OpAmp.
Instead of using chopper stabilization, this differential pair is also temperature stabilized to achieve a certain degree of stability. Clever idea, .. I think this was later realized in an integrated OpAmp from National, or Fairchild, maybe µA 714, or earlier.

Certainly, this Zener diode CR13 has drifted over these 50 years, i.e. its voltage has increased. Maybe also the ww range resistor R11 = 5200 Ohm has decreased..

But there's absolutely no need to crack the oven open for calibration.

R80 and R83 are intended to do the coarse calibration of the range.
Simply measure the Zener diode voltage, and chose these resistors, that the value in kOhm of the complete range string R80 + (R11 || R83) + 1/2 * (R12 || R79) (roughly 5.3kOhm) equals the voltage value (roughly 5.3V).

Then, the linearity of the sample string (10k + 10 x 1k / 100 / 10 / 1 + vernier 1 Ohm) should be checked, i.e. whether it still achieves 0.1% linearity..

Maybe, that the gain (beta) of several of the transistors (outside the oven) also decreased greatly, as this is a typical effect of such old components.

This, and also dried out capacitors, may lead to an unstable output.

But anyhow, I also would like to see a characterization of this historic (?)  instrument, after this easy calibration!

Frank

[geo_leeman]

Great video! I love old PSUs.  I did have a similar issue with another supply recently of not being able to tweak it into cal.  I removed the jumpers on the back, gently polished the contacts with some fine scotch-brite pad and reassembled.  That was all it took.  Some corrosion was messing with the sense and it was quickly brought dead onto spec. 

[robrenz]

I have done multi day and week long burn ins of these units at full load without any capacitor issues so I would not just replace caps because of age.

After a 30 hour burn in at max amps and voltage then calibrated using my Fluke 8846A before I sold this one on the forum.  incredible performance   (All switches were given a cleaning and 2 step deoxit treatment.)

0V = 0.2 µV 
20V = 20.0001V   
10V = 9.9998V
5V = 5.00000V
1V = 1.000095V
0.1V = .0999999V

It was the later model "A" version with the edge meters and pull to set current controls.

[don.r]

As for the unit being out of spec, are you still as "In Spec" as you were at 18? Most likely not. Couple things come to mind. The electrolytic caps are due for a change, and those carbon resistors are going to drift. You could do the lazy mans job (And in this case its the way I would probably go) and bodge in a resistor to bring the divider string into cal, replace the filter capacitors, and call it a day.

Yes, will probably do at least that. But would be nice to hunt down the drifting culprit.

On my 2020B it was one of the carbon resistors in the divider that went south. I replaced it with a pair of hand picked 1%'ers.

[artag]

Good to see this. I hadn't realised how well-loved they are : I've had a 5020 for several years, bought for not much at a hamfest. It works fine, though I've never checked the cal.

[K6TR]

Nice score Dave. Regarding your unit being out of spec I don't have anything new leads for you from what already has been pointed out but will state for emphasis to focus on the Carbon Composition Resistors. I think you would find it very revealing if you removed one and checked it's impedance.  Yes that's right I used the word impedance. Carbon Comps are notorious for not only drifting out of spec but adding reactance as they age. That's part of the reason they stopped making them and went over to metal oxide film resistors.

As to the capacitors they were built far more robust with a longer intended life time but still can fail. They often fail not outright but become noisy.

I sure would welcome a follow-up video to see what you found wrong with it.

[Rutger]

Wonder what the ESR is on those old caps?  I would like to see a calibration/repair on this unit and a review of the individual components, like are they still in spec?

[Agent24]

Add another vote for checking the resistors. I have some bags of quite old resistors and while sorting and testing them I found that quite a few of the values have increased in value even just sitting there unused.

[yym]

The problem is obviously the ovenized reference oscillator (at 8:33) 

[IuriC]

The schematic image link you provided is too tiny. Here is the big one image:

http://www.rako.com/Articles/images/Power_Designs_Model_2005_Schematic.gif

[bob_60]

Again a nice video from you Dave.

When I think back, you have made quite a few videos about different power supplies, and I think I have probably seen them all.

With all those different power supplies, what about making some videos where you look at how the regulating circuits - in detail - is actually designed in the different supplies. In your u-power supply series, you choose an IC as the main regulator, but what designs does the power-supply manufactures choose. And what has changed design-wise - if anything - in the last maybe 20 years.

Personally I would also find it interesting to see how good regulating circuit designs differ from cheap designs like for example the Korad KE300 you have tested - and I'm not thinking of the quality of the connectors, components, the chassis etc. - just the design of the regulating circuit itself.

/Bo

[aroby]

I loved the look of this, so I bought one from eBay.  Got it for $50 because it didn't work.  I just received it - it needs a clean and there are some scratches on the front.  And it only doesn't work because there is no fuse in the fuse holder at the back.  I shorted it out, powered it up and it seems to work fine. The dials were set to .0316v and that's what my meter measured!

The unit seems to be older than Dave's - only one fuse holder on the back and the serial is low down vs high up.  Once I get it cleaned up I'll see what other differences there are.

Anthony

[Macbeth]

Love it. Nice piece of gear that.
I remember back in 1985 at University learning Electronic Engineering I had to do a section on loom wiring and lacing up just like that power supply. Fantastic, IWOOT!

Haha, I remember learning how to lace looms as part of my City & Guilds back in the late 80s/early 90s. It seemed so anachronistic then, but had to be done as a practical  Get the stitching more than a few mm out and lose points!

[SeanB]

If you work on aircraft you learn how to do wire knitting on looms, especially if you have to either replace a wire or add a new one as part of a modification, or if the wire breaks inside the loom. Had plenty of practise changing plugs and sockets as well, where you have up to 200 wires, all white, all the same size and all with the hot stamped lettering that was applied in production ( each wire is individually labelled every 10cm with a designation of the loom, section and wire number with a hot foil stamper) worn off by chafing in the loom. Simplest was to get the new connector, align correctly (round multipole connector with 4 possible ways to mount it, and with 16 variants as to the inner alignment and locating slots as well) and do each wire one by one, use the extract tool to release the connector from the shell, cut the connector off, strip, solder or crimp as required then insert in the new one. Generally inside a panel and with large amounts of other stuff in the way, and often knee deep in hydraulic oil and fuel. for more fun with a hot engine as well for company, and you lying on top of the cowling working inside an access panel with 40 screws holding it. Cable ties not allowed, they work loose or cut into the looms. Still have some rolls of the waxed twine and the needles, handy to do leather work with.