Another Lambda LQD-421 repair

[GumGum]

Hi,
I have a half-broken LQD-421, the power supply part works fine however I can't get the front multimeter to work properly. It has a zero-offset of ~1.2V and behaves non-linear through its range. The 100mV reference is fine and I can get it to display the current voltage just fine, however it drifts as soon as I set another one.
The problem is present on both sides. I've already replaced IC201 (FBT-00-074) with a ICL7107CPL and Q201 (FBN-L199) with a 2N2907, the problem got better but still exists. All other parts seem to be fine as far as I can tell.
The only thing I found that the Voltage near R221 is -5V instead of -5.9V as written in the schematics.
Any ideas where the problem might be?

Thanks!
Luka

[cnqhdszq]

check the V–I switch
drop a drop of oil in it
maybe can solve the problem.

[macboy]

I have a 422. Check the power supply voltages to the meter section. Check DC level and AC ripple. Dried up capacitors are a big problem with these in my experience. Do you have the service manual? I can post or email if not.

[GumGum]

Good point, but I've already tried that. (This was actually a problem on a another Lambda I had)

[GumGum]

The voltages seemed fine, however I haven't checked  them for ripple, will do that.
I have only the one I attached, If you have a more detailed one I'll be happy if you could send it to me.
Thanks!

[GumGum]

Sooo, I checked for ripple and the 5V between B30 and B27 are fine. Between B27 and B29 there is some ripple present however I checked C109 and it's fine (I also replaced it but nothing changed, with only 40uF  and one diode some ripple is to be expected I think)
Then I took out the whole Meter PCB and powered it via a Bench Power Supply but the symptoms remain the same. The offset remains even when B28 and B32 are shorted.
Any thoughts? Thanks!