EDC VS-111R from government employee to you know photographs, nudge, nudge

[babysitter]

This beauty, having a nice career in the late 60s, early seventies, was recently up for sale on ebay.

Its a precision voltage source claiming 0,01% accuracy. You will see from the asset tag that it used to work for a US gubberment agency, but someone lost its trust in it in 1974, leading to a decline in career.





The ebay picture didnt give away a impact wound on the bottom side, cutting open the aluminium enclosure on a length of approx. 2cm and pushing the metal in about 1 cm. Must have hurt and made me wonder if it will still work.

The hit, however, went to free air, so nothing else got hurted but the whole unit will have experienced some G force I am afraid. However, the nice power-up made those worries basically disappear. As I just moved a few months ago, a bit of painters filling was available so the sheet got straightened out with a bench vise, pliers and a hammer, and the hole stuffed with painters filling which was going to be covered in black. Putting black on it happened just today during the photoshoot, with a simple Edding sharpie:

[babysitter]

I din't power up immediately to mains but used a variac to apply mains voltage rising slowly over the course of about 5-6hrs. Watching a amperemeter during the first minutes of every voltage step and listening to explosions inside, i hoped to prevent damage from f*cked up electrolytic capacitors.

Also, as it is a american thing I ordered a cheap autotransformer to get 115V out of our 240V mains. No bad surprises, at some voltage level the STANDBY light came on and went on and off and on and off, suggesting that it is somehow connected to a oven.

At full mains voltage, it worked satisfying. The 3.5 digit meter I used was happy.
However, as it is a american unable to adapt to german behaviour and mains voltage I bought a cheap autotransformer from Amazon to operate it on german 240V mains, giving it a feeling of home - but still at 50Hz instead of 60 Hz.

[babysitter]

This thread would be only half as hot without a photo of the backside:



The label doesn't give away, but the datecode of some parts inside suggests that it was born in 1967 or shortly after.

(Don't turn around your monitor, get off your chair and do something for your health!)

[babysitter]

Now, lets undress:


Look what we see here on top...

This seems to be the board where the magic happens. Curiously, no adjustments done here at all! So all is done by selecting parts, I figure.

Resistance and switches!
A resistor chain will set the output voltage.






In the last image, the lower switch (top right in the image) selects positive output, zero or negative output.


This poti+switch combo either selects unpotied output voltage out or a vernier for plus minus one milivolt.

[babysitter]

Power supply PCB:


Atomic electrolytics!



Upskirt! Bottom side of the power supply PCB:

[babysitter]

Inside of the output terminal sockets: force and sense wiring


The big metal-covered thing on the top PCB is somewhat ominous. A bayonet shape and the visible spring inside suggested that you can remove it. What is this?

[Vgkid]

The blue can is most likely a mechanical chopper relay. Chopper in a chopper amp.

[SeanB]

Yes, chopper relay. You will be changing every yellow cased electrolytic, along with every capacitor with a rubber end seal and a rolled crimp on that bung. The round items with soldered ends and glass seals are going to be either wet slug tantalum capacitors, oil filled polystyrene capacitors or precision resistors. They will all most likely still be within tolerance and good for another century of work. There is one adjustment on the reference board, the 20 turn pot at the top left with the 2 scres holding it to the board. There is a small screwdriver slot in the top side, to adjust the reference voltage to within spec. Do not adjust it, it will still be correct when the dying electrolytics have been replaced. Sadly you should check every one of those carbon composition resistors ( though in circuit will work for most, they always drift high so check if the resistance is less than the rated value as a rough check) for drift, I checked some NOS ones a month ago before using them, and they all had drifted to between plus 5% to plus 10% of the nominal value after around 40 years in storage. Still used them, as I could live with a +30% drift in that use as current limiting resistors.

[babysitter]

@Vgkid: Yeah, very plausible due to the schematic on it 

Some quick and dirty statistics will follow, family time now...

[babysitter]

Progress: 1/3rd of the relevant capacitors I have, the rest will be ordered this week, I identified two missing screws as possibly #6-32 and my favourite fitter is looking for them.

[xrunner]

Cool project - I'll be watching this one. 

[KM4FER]

Now that's electronics !    None of the newfangled little black boxes with a Gajillion legs sticking out so close together that there is no way these old eyes of mine can possibly count them.  Just basic components; resistors, capacitors, switches and .... and ....  wait a minute looks like a couple of those trans-is-tory things in there.  Where's the vacuum tubes (valves)?  If it don't glow in the dark and heat your house in the winter then it can't be any good.  Better throw it in the trash.

Ahhh, to have my youth back.

[babysitter]

Although there are a lot of suspicious electrolytics, its health is quite okay:

Statistics

I had it running (with old caps) for a while vs a HP3456A, needed to edit out some user fiddling. No bad performance for a old lady set to 10V:

Average 9,9992586932 V
Median 9,99924V
Standard Deviation 4,53976440167085E-005
Span 0,00038V

Duration ~35 hrs, sample interval 10s, either 100 or 10NPLC - I don't remember :-/

[babysitter]

  Is it just me or are NEMA 5-15 sockets and plugs dangerous?

I'm used to those nice german CEE 7/3 and 7/4 with complete shroud and contacts recessed so deep that even with a CEE 7/16 you will not have live contacts exposed ever. However, I bought a autotransformer device with the usual US socket with the completely flat faceplate.

The contacts of the socket seem to be recessed not enough as inserting the plug incompletely gives exposed plug contacts that at least my little ones could touch? (Edit: Circuit completely closed with 10 mm exposed contacts - gap big enough for me to get my finger in! )

This strengthens my opinion that I should do a proper europification with the autotransformer retrofitted inside the enclosure and 230V rated mains cable, and covering the original transformers wiring with shrinking tube in the process as it looks somewhat insufficient to me.

Edit 1:The Autotransformer might like being connected to a bigger metal surface for cooling as right now, the plastic housing gests reasonably warm, I guess some 30°C - who does rate a transformer for 150W instead of VA? Seems like the seller even downrated it out of guilt as the model number is KXT-200


Edit 2: I filed a report to the product safety office - they will decide 

[T3sl4co1l]

Yes, you can stick your finger in a NEMA XXX plug as it mates.  I suppose people don't care too much as it's only 120V (yes, 240V between 'hot' prongs on the bigger ones, but perhaps that's less likely to be a problem as you'd have to be grabbing it with both hands?).  We don't ordinarily have to protect against the 240V to ground that you guys do!

Comes to mind, even the twist-lock three phase (including 480VAC!) types have bare prongs of pretty much the same length.  So it could be that we're dumber than the average on things, too.

You see the massive, shrouded, round prongs and locking or threaded receptacles from time to time, but they're fucking expensive ($300 vs. $30 for the same ratings, IEC vs. NEMA), so who even gives a shit?

But I digress.

Tim

[T3sl4co1l]

Look what we see here on top...

http://www.primeintrag.org/dg3hda/VS-111R/naked-top overview.jpg

This seems to be the board where the magic happens. Curiously, no adjustments done here at all! So all is done by selecting parts, I figure.

Hmmmmm, what's under the tube shield?  Looks flat and shiny on top, perhaps not a tube... but perhaps still something hermetically sealed?  The magic sauce?

Tim

[EEVblog]

Urgh, the corrosion on those switch wiper contacts 

[babysitter]

Yes, you can stick your finger in a NEMA XXX plug as it mates. (...)
But I digress.

Tim

So this is normal? Interesting.

I intend to remove the autotransformer from the enclosure and mount it right inside the Voltage reference. There are some unused drill holes in the aluminium chassis, maybe I use a angle bracket there, or put it right to the inside of the enclosure wall to separate its magnetic field and heat from the circuit.

Hmmmmm, what's under the tube shield?  Looks flat and shiny on top, perhaps not a tube... but perhaps still something hermetically sealed?  The magic sauce?

Tim

Its the big blue (estimated to be a chopper-) relay that you see in the other picture, with the schematic printed on its side.
Maybe something mercury-y? There is a wire pair right in the proximity of the relay going to the transformer, suggesting it toggles along at mains frequency or mains frequency times 2.

The lower PCB, however, is not just power supply, one end of the switchable resistor chain goes there, right next to one more ww precision resistor.

[babysitter]

Urgh, the corrosion on those switch wiper contacts 

Imperfect lighting, it is not eevblog studios Haven't spotted any nasty residues of anything yet. Switches look better in reality, will take some more pictures. Only bad thing is the trace where the contacts kind of scratch. considering a treatment with Teslanol Oszillin T6.

Edit: poti porn.jpg looks more like the real thing. Wonder what reflections gave that orangeish tint.

[babysitter]

The former external autotransformer now is inside, and also donated its SchuKo mains cable.
The aluminium angle brackts had been glued to the xformer with epoxy glue. The brackets and metal case will do a great cooling job although he was not too unhappy in his former plastic box.

I hope they dont do a magnetic dance due to the proximity as both coils see each other with "perfect alignment", perpendicular installation might have been better on second thought.
The mains inlet will first go to the autotransformer, this will feed the EDC original. The original earth bonding point will be used again, but the autotransformer might get its own protechtive earth connection if resistance between earth pin plug and prodtruding screws is too high without.

[Bryan]

In the last picture, just below the blue cap? there looks to be what is a diode. I wonder why the odd crimped loop on the end side of the diode?

[dom0]

In the last picture, just below the blue cap? there looks to be what is a diode. I wonder why the odd crimped loop on the end side of the diode?

Strain relief

Also, better insulation against the soldering shock due to the longer leads.

[babysitter]

DONE - SO FAR.

The Autotransformer is mounted and connected now. However, the 110V type Transformer might be a bit on the wimpy side isolation-wise, as german mains plugs are not polarized it would get 240V against earth if the common point of the autotransformutitator is on phase instead of neutral. I measured which side is neutral in my home and need to take care. When the bank account recovered from the car accident etc. I reconsider getting a replacement transformer for europe.