Would you pay $100 for a HP6115A psu ?

[alm]

Which thread is that ? Mind pointing that out please.

Sorry, don't have a link handy and don't have time to dig it up. Your Google should work just as well as mine. I think it was based on AN86.

Still that programmer output range at +/- 10V, high voltage like at 50 or even 100V is quite challenging isn't it ?

They use a trick to scale the voltage up to the desired range. Don't remember the details, see the 59501A manual. I guess you could use the same trick with whatever programmer you decide to build. Of course scaling up the output it will make the system more sensitive to noise and offsets, and the scaling resistors will need to be stable.

[saturation]

Bravo, thanks a ton for the stitched schematic.  The amount of time I saved perusing the circuits was so great, I should have done this myself a while back. 

[mmagin]

Thanks so much for the stitched schematic.  I was suffering with the unstitched one for a couple evenings.

I have a 6115A which needed a new C2 for correct +/- 28V reference supplies, but I still don't have the 16V supply properly adjustable, it stays stuck at 19V.  I seem to have a later rev of the A2 board, and the R3 is already populated, though I tried shorting it too and the problem remains.  I need to do some measurements and see if it is inputting what it should to the op-amp or if the op-amp is possibly bad.  Q1 and Q2 at least pass the usual diode-test checks and the surrounding passives test correctly.

That may be all that's wrong with the supply, it currently outputs too high of a voltage, and before I proceed with checks and adjustment the 16V supply is the priority.

(As an aside, I'm so glad I got a DE-5000 LCR meter!)

[BravoV]

mmagin, my pleasure.

What happened to the C2 ?

Also if you don't mind to share the problems you encountered and the fixes if you've done it here.

[mmagin]

mmagin, my pleasure.

What happened to the C2 ?

Also if you don't mind to share the problems you encountered and the fixes if you've done it here.

C2 just suffered the usual high ESR of old capacitors.  Others are nominally okay so I left them for now.  A2U1, which via web searches I cross referenced to a NTE part and then to the LM741 (essentially identical specs) seems to have had a failure of its output stage, it wasn't able to pull down R7 to affect the Q1/Q2 pass transistors (verified before I replaced it by lifting the lead of R7 and measuring its output.)

With the op-amp replaced (Digikey still has the metal-can 741, didn't have to go to shady ebay sellers or make up an adapter board!), I've adjusted the 16 volt supply to within a few millivolts.  I'm going to have to go through all the adjustments once it's fully warmed up to get it back into proper shape, but the output is only off by about 0.13% to 0.23% depending on what part of the output range it is in.

Not sure if perhaps the failed capacitor and insufficient filtering of the +28V rail led to the failure of the opamp, may think about replacing all of the electrolytic capacitors.  hmm.

[mmagin]

Also, C1, the 1 uF film cap across the transformer was making a dreadful amount of buzzing noise.  At first I thought it was the transformer, but I only heard it from one side and I actually could feel the vibration on the capacitor!

Replacing it with a (higher voltage spec, but not too huge) 1uF film capacitor I had on hand has made the supply silent.  Hurray.

[mmagin]

Yep, 1 film cap, 1 electrolytic cap, 1 op-amp and it's back to working correctly and was successful at adjusting it.   I think the millivolts pot may be a bit cruddy, but things seem to basically be correct and the regulation is very solid. 

Still intending to replace the other electrolytics someday, but not right now.  The two large screw-terminal caps seem to use a terminal spacing that is no longer the standard.  Sadly the ones I paid darned good money for are just a little too wide to fit.  I'm thinking about making an adapter PC board to replace each with 2-4 smaller leaded electrolytics each plus a screw, nut, and a brass spacer to give similar standoff distance.  I discovered that there are tin-plated solderable standoffs available with a nice shoulder to fit in a hole in a board, but none commonly available quite as large as I would want to replace screw-terminal caps.

[bitseeker]

If you do go with the adapter board, do post your results here. I recall someone had fit components into some vintage HP gear by soldering to the beautiful gold pads/traces because the original screw contacts didn't fit. So, an adapter would be nice to see.

[mmagin]

If you do go with the adapter board, do post your results here. I recall someone had fit components into some vintage HP gear by soldering to the beautiful gold pads/traces because the original screw contacts didn't fit. So, an adapter would be nice to see.

If I do I will certainly share KiCAD files (and probably an OSHPark shared project too).

[bitseeker]

Fantastic!

When I one day get a 6115A to keep my 6114A company, that adapter may come in handy.

[Peter_O]

Just got an 1986 HP6114A in good condition. Voltage is off <40mV. Stability at 12V is <100µV over 10h, if I can trust my 5.5 digit DMM.

1
The voltage switch seems to have some contact problems. For a lot positions the voltage is floating within the respective digit. When giving a little pressure to move towards the switching point, the voltage stabilizes.

Any advice to get the switch running again and not damaging it?
Maybe contact spray is the wrong approach.

2
There is some chirping noise from the transformator. Something I should do with that?

[coppercone2]

No, the front panel interface with all those switches is a complete pain in the ass if anything goes wrong with it. Quite frankly, those switches suck. If the replacements were cheap maybe, but you are going to get robbed buying replacements for those. Replacing them is extremely annoying also. Taking them apart is even worse, expect crappy brittle plastic, if you want to service them with grease and cleaning, there is a good chance of damage.

[Peter_O]

Not that encouraging. Thx anyway!

I had the idea to spray some non agressive cleaning stuff into these guys without taking them apart.
Eg. Kontakt 61 (not the agressive Kontakt 60) or Teslanol® T6-OSZILLIN.

[coppercone2]

you can do it, just.. you need to be REAL careful

for 60? year old plastic you don't have that much leeway. Dunno if that will get in there, they are not service friendly. I think you need to take them apart and carefully wipe that brass. Mine had like, fossilized shmoo. But my switch was dicky and when I took it apart and put it back together, the front end control circuit broke, so I decided fuck this thing and scrapped it. It would be going back and forth between the control circuit and the front panel. Now you could replace that nice resistor network with a potentiometer set as a rheostat and.. forget about the precision... but the amplifiers in there not that impressive. I really dislike how the stuff in the front is just pressed tight into a wedge like a garage door too. Needs screws.

Its like 4 spring loaded multimeters that shoot plastic out.


GOd, when I look at robrenz restorations, I feel like I bought a fucking giant dilapidated apartment projects complex. I wanna throw all my shit in a swimming pool and stir it with a boat paddle. 

[Peter_O]

It's a later year, 1986. So just 35 years.  :-)
But from the odor it seems to have some smoker's years in it's vita.

I think, I'll give it a try with the non aggressive cleaner. If that does not work, I can always follow that nice restauration report and take the stuff apart. Maybe I'm lucky. ("Well punk, do you think, ..."     )

[bitseeker]

So, did ya get lucky?

[Peter_O]

So, did ya get lucky?

Yes, I did. 

I took the switch block apart and blew some Teslanol® T6-OSZILLIN and compressed air through existing holes of the switches. Same with the meter input switch.
Now it's working perfectly fine, as my other new old companion, a 3455 for 140 Euro incl. shipment, shows. E.g. 5V stay within +/- 20µV over an hour.

[coppercone2]

ah, you did not take the switch bank apart like I did. I should have left it alone but the inside was filled with chunky grease.

I should have put it in a bag of oil, ultrasonic it, and flush it with a generous amount of oil then like spin dried it

is there a safe solvent to totally soak plastics in that will dissolve old grease? I figure alcohol would crack the casing. I dunno if you can just throw it into a cup of warm WD40 or something.

[Peter_O]

ah, you did not take the switch bank apart like I did. I should have left it alone but the inside was filled with chunky grease.

I read your restauration report with great interest and it encouraged me to start desoldering the whole switch assembly.
I took the bank apart but did not open the switches.

is there a safe solvent to totally soak plastics in that will dissolve old grease? I figure alcohol would crack the casing. I dunno if you can just throw it into a cup of warm WD40 or something.

I decided to use Telsanol, as it is described to be not agressive but to clean and lubricate. There were some encouringing posts in german forums. It seems to lubricate the plastics to some extend, at least the black got darker. The cleaning results are excellent. Just a short spray into the switch, some full switching cycles and every position is making perfect contact again. Before cleaning the .1 switch was so bad that I feared, there might be no pcb track left.


Now there is only the chirping noise from the transformator area left. Maybe I take the idea from somewhere above and try a new 1µF film capacitor.

[coppercone2]

what bugs me about not taking it apart is that there were like.. chunks in there. It looked like old fat on a frying pan that got used dirty too many times. I imagine if you don't fully open and flush it, they would just be sitting in the bottom of a switch.

If its totally dormant or benign I don't know, but it sure bothered me. I had to scrub mine with a brush with alcohol to get it all off. If you can handle not knowing whats in there, or not being bothered by a little bit of orange grease, you are fine.

To be honest I did full cleanup of mechanical gearbox before, and its satisfying while its open, but when you re-grease it it ends up looking like shit anyway. The switch gets almost no use compared to a gear box though, so I don't think you have traditional gear box problems of grease loaded with metal, its just some what oxidized. But having the switch fully open lets you put like.. actual grease in there (i.e. like smear). So theoretically it should offer a longer life. What I know with multimeters is you are supposed to take them apart and put actual grease there. If the lubricant you used has a similar staying power its fine.

I recommend just living with it and NOT taking the switch apart because its hardly anything. I just think the solution they did with that switch is pretty bad.

Don't even know if you will live long enough to re service that switch anyway... based on how well they last. OCD hurts here

If you can't help yourself beware there is a little brass plate there that is fitted over some thin plastic pegs. robrenz has a photo of it. If you take the switch apart, you won't know exactly where to put the brass plate (it has multiple alignment holes that all fit over the pegs), so you will have a offset. Its perilous. The spring shoots plastic out, its held in kinda loosely also. And IIRC they don't always snap back together so you might have a plastic welding job there. You need to like tap on the top to make sure the little brass plate is not stuck to the top while you lift the top of so it remains correctly positioned. Don't haphazardly put it back together if you mess up.

I musta put it back together or just deformed something that prevented the front panel from working right, so I tried to replace it with a helipot, but then there was another problem and I lost my cool. Maybe if I took a break for a month and left it on a shelf i coulda had it back together working with a few minor repairs. But I also think some time during this madness I lost a spring.

[Peter_O]

Don't even know if you will live long enough to re service that switch anyway... based on how well they last. OCD hurts here

Meanwhile the solvents should have vaporated and the switches are still fine. I will let it rest for now.

But I managed to cure the chirping sound from the trafo area. It was the 1µF foil capacitor.