Wandel & Goltermann SPM-19 Repair

[Simon_RL]

I have got my hands on a Wandel & Goltermann SPM-19. It is in pretty good condition and am keen to getting working. This is the one Dave had and grabbed it when he was giving away stuff from his old lab.

It is a magnificent piece of engineering and I couldn’t let it go into the dumpster. I have only eye balled the innards, except for the power supply and cannot see anything untoward. Before I start poking around for real I want to get the power supply up and running or replace it. I would like to try and keep it as original as possible, being a purist, which leads to my actual question. I have been searching for the last couple of weeks and cannot find anything. Can anyone suggest shops or individuals that sell this sort of old gear or parts. I know this is a long shot, but any help would be greatly appreciated.

[wn1fju]

I don't have a direct answer about who sells parts for these, but I will relate what I did with my SPM-19.

When received, it wouldn't power up, so I pulled out the power supply and disassembled it.  What I found was that one or two of the main filter caps in the switching supply had spewed their guts.  It wasn't a little fluid or crusty powder like one sees with small electrolytics, but rather a lot of thick oil was sprayed all over the components.  Moreover, it must have sat for a while in this condition, and the oil was caustic, because it ate through a lot of the wire insulation - and the wiring was pretty pervasive throughout the supply.

I managed to replace the caps and clean it up as best as I could and the SPM-19 ran fine for a few weeks before the power supply died again.

This time, I junked the power supply and replaced it with a Meanwell RQ-125 switching supply.  I had to add a 7806 6V regulator, a transistor switch, a relay and a battery holder (2xAA).  In fact, it was good that I now just opened the unit up to take a photo, because clearly the batteries have leaked and need to be replaced!

Other than the power supply, over the years I have had a few logic chips go bad and one tantalum capacitor that exploded.

[Simon_RL]

I don't have a direct answer about who sells parts for these, but I will relate what I did with my SPM-19.

When received, it wouldn't power up, so I pulled out the power supply and disassembled it.  What I found was that one or two of the main filter caps in the switching supply had spewed their guts.  It wasn't a little fluid or crusty powder like one sees with small electrolytics, but rather a lot of thick oil was sprayed all over the components.  Moreover, it must have sat for a while in this condition, and the oil was caustic, because it ate through a lot of the wire insulation - and the wiring was pretty pervasive throughout the supply.

I managed to replace the caps and clean it up as best as I could and the SPM-19 ran fine for a few weeks before the power supply died again.

This time, I junked the power supply and replaced it with a Meanwell RQ-125 switching supply.  I had to add a 7806 6V regulator, a transistor switch, a relay and a battery holder (2xAA).  In fact, it was good that I now just opened the unit up to take a photo, because clearly the batteries have leaked and need to be replaced!

Other than the power supply, over the years I have had a few logic chips go bad and one tantalum capacitor that exploded.

Thanks heaps wn1fju, I greatly appreciate the info and photo provided. I am expecting similar problems with the power supply in my unit, with it being so old. Thanks for the info about the replacement MW psu and components.

One issue is the power switch is broken, can you advise if there are any specific considerations for this switch?

[wn1fju]

As far as the power switch goes, if I remember correctly the front panel "switch" merely acts like a plunger.  It presses on the post of the actual power switch, presumably embedded in the actual (removable) power supply carcass.  I wish I had saved the original W&G supply so I can verify that, but take a look on yours.

What I ended up doing when I removed the original supply was to mount a standard push on/off type switch (like one finds in almost every piece of vintage HP test equipment for instance) right behind the plunger.  I think I used a DPDT, although a DPST will work fine (both the line and neutral are switched).

I'm not sure how easy it would be to fix the plunger part.  The actual switch, however, should be fairly easy to replace.

I have a few other W&G pieces and although the switch housing looks similar, there is no plunger and wires disappear into the actual switch.  So I guess they are a different type although they look the same from the front panel.  Those pieces don't use a self-contained power supply, but distribute the supply over a few exposed boards.  So I guess they can simply put the switch right on the front panel and don't have to worry about transferring the mechanism into the power supply. 

Of course, I could be completely wrong about all of this - it has been a few years since I played around with the W&G stuff.

[navigoavela]

please can you send the schematic of the connector from power supply ?
I must replace the power unit too but i ignore wiring except ground.
navigoavela@gmail.com
tanks tanks

[navigoavela]

power flash and whist so the entire instrument flash (display leds).
Capacitors seems
 in good state but i dont know if they loss capacity.
Help

[navigoavela]

tanks for the exaustive private message....
tanks from the soul of mr Golterman and from mr Wandell that now can sleep in peace because i dont demage other.

[pag]

Nice job with the power supply.

I have two of these units.  The first one had bad leakage from the nicads which heavily corroded the power supply.  I spent days disassembling and cleaning it all out.  Then found several bad rectifiers.  Had it running on the bench for about half an hour then it blew the fuse.  Turns out the main transformer shorted out in one of its windings.  Put the unit aside.

A friend had bought one of these cheap at a hamfest but it kept giving him errors so he gave it to me.  They are about a year apart in production yet many boards are visibly different.  Swapping boards would not be easy as they have different connections.

I tried using the good power supply on mine but it, too, reported many errors.  Both units behave the same in that they report various errors which change.

I did locate a copy of the German service manual on one site and partial schematics on another (poor scans).  I can send if you haven't found them.

The schematics are, of course, different in many cases from either of my units.

Running functional test gives any one of a series of errors like 1-004, or 1-001 and so forth.  Google image translate helped me narrow down to the area of the issue but those areas seem to check out OK and consistent.  And why the exact same errors in both?  No, it's not the power supply as it looks good and I tried substituting lab supplies from my bench with the same results.

It might be an issue with cal factors being too far off.  Adjustments will require extensive translation and I'm not sure I want to spend that much time on a German version of a HP 3586 SLM.  I mean, it looks cool...