Keithley 155 Null Detector - Repair and Restauration attempt

[donlisms]

...
In old days they often used just a sensitive moving coil galvanometer without any extra series resistor for the sensitive part. The one with optical readout and light pointer are really sensitive - I remember some thing like 1 mV full scale, and this was not an extra sensitive one. ...

Oh, yes - the galvanometer being a current device, with sensitivity into the nanoamps or perhaps into the picoamps, some very precise measurements were possible with these stone knives and bearskins.  Meter sensitivity might be given in megaohms per scale division @ 1 volt, with measures of hundreds or even thousands in some cases.  Frightening. 

[Don Victorio]

They there,
just signed in here. Thanks a lot for asking, it was me who bought the Keithleys to bring them back to life 

I worked with this device before and need them for some specific purposes. After looking for them for about 5 years, I got pretty bored searching EBAY and decided to bring that to an end. Congratulations to the seller.

Not cheap that's for sure, but a nice project for me.

So far I found a faulty capacitor and replaced the other electrolytic and tantalum ones.

I'm not a professional expert, but until now I managed to repair all devices from that age, I had in my hands. Nevertheless, I'm always very thankful for advices concerning possible defects.

One seems to work somehow but range selection doesn't fit at all to the applied voltage (changed capacitors so far).
The analogue display of the other one is stuck at one end of the display.

My idea is so far:
Changing caps and after that checking potentiometers. Then working through the manual and test points and maybe finding a fried diode.

Does anyone have a full parts list? Especially transistors seem to be chosen by the factory  . Never saw that before.

I constructed a battery holder for a 3D-printer. Feel free to mail me for the .stl. If you don't have a 3D-printer, we'll find a solution for that too 

I'll post pictures of the battery's holder recent version within the next days.

[lowimpedance]

I constructed a battery holder for a 3D-printer. Feel free to mail me for the .stl. If you don't have a 3D-printer, we'll find a solution for that too 

I'll post pictures of the battery's holder recent version within the next days.

You can post the stl here with pic's (place it in a ZIP)

Also see here for my 9V K155 battery holder
https://www.eevblog.com/forum/metrology/keithley-k155-battery-holder-3d-model/

[HighVoltage]

Thanks a lot for asking, it was me who bought the Keithleys to bring them back to life 

Welcome to the eevblog forum, Don Victorio and congratulations on the two Keithley's

Yes, please share some pictures from the inside and your repair steps.
The schematics are available, see attachment