Attached is a schematic of a multimeter section of a SWTP Universal Digital Equipment kit (70s vintage). The circuits in violet are what I suspect are the cause of a malfunction. Fortunately I was able to find a functioning unit and found several discrepancies in the original schematic. The malfunction is that with no input on IN there should be a 1Hz or less pulse on pin C . At least that's my understanding. If I pull IC3 I get an approx. 2Hz pulse. Measuring pin 2 of IC3, IC removed the reading is 0V. IC3 installed the reading on pin2 is approx. 2.4V. I've checked the continuity of Q6-8, D3, D9, D10. I'm awaiting parts to breadboard this section but in the meantime I'm feeling pretty incompetent.
Note: The section in the lower Left(in violet) is, I'm 99% sure, the constant current source for the Ohmmeter function which at the moment doesn't appear to be working.
Note: The section in the lower Left(in violet) is, I'm 99% sure, the constant current source for the Ohmmeter function which at the moment doesn't appear to be working.