Hello OM,
1.Check the 5V power supply on the 4.pin of the IC 201 opamp.If its missing,maybe the Z201 5v1 zener diode is defective.
2.Check the output voltage on the pin 6 (0-700 mV)
3.Check the Non inv (3 pin ) and the inv input (2 pin) voltages .
4.Check the resistor divider chain.
Does the offset potentiometer (p101) work?Can you adjust the zero ohm?
Good luck to repair! '73
TJ https://elektrotanya.com/iskra_unimer-31_multimeter_sm.djvu/download.html
Hello OM,
1.Check the 5V power supply on the 4.pin of the IC 201 opamp.If its missing,maybe the Z201 5v1 zener diode is defective.
2.Check the output voltage on the pin 6 (0-700 mV)
3.Check the Non inv (3 pin ) and the inv input (2 pin) voltages .
4.Check the resistor divider chain.
Does the offset potentiometer (p101) work?Can you adjust the zero ohm?
Good luck to repair! '73
TJ
https://elektrotanya.com/iskra_unimer-31_multimeter_sm.djvu/download.html