Looking closely at the service manual for the 87V I've discovered that the two models share a lot of things.
One thing that really caught my attention is that the meter doesn't seem to know where the switch is positioned.
Broken meter:
Working meter with the switch in between 2 positions:
Here is the switch selection from 87V:
I could trace everything that you can see in the little diagram above except for one thing SWPOS (conected to PIN 5 on MSP). If I measure from pin 5 of MSP to meter GND (-2.5V in reference with COM) I get exactly 1M ohm but I can't find where that resistor is.
Since I couldn't find the resistor "R22", I wasn't able to trace the dirrect connection (if it is the same as the 87V) between pin 5 of MSP and contacts (perhaps switch pads) 15,19,23,25,23.
Now, comparing with a good working unit, if I measure from COM to pin 5 of MSP I get the following voltages:
VAC 0.145V
VDC 0.45V
mV 0.74V
Ohm 1.01V
Continuity 1.31V
mA 1.63V
A 2.02V
In between any swtich position I get 2.5V, which is right. I was hoping at first that on pin 5 I have permanent 2.5V and the meter doesn't know where the switch is positioned. Unfortunately, that came out false. All of the above voltages are present and match very closely on the good unit as well, so I still don't know what is wrong. Basicly, the voltage at pin 5 tells me that the meter is informed correctly about where the switch is positioned but it can't do anything about it.