EML 101 / UA726 help

[mkiijam]

I have no output on EXP 3 (VCF). I believe the uA726 is the fault, because there is nothing on PIN 9 and there is the correct signal on PIN 10. Can I swap this out with some standard transistor as it is not using the matched pair?

 

[radardoug]

Pin 9 is the inverting input of the opamp and is a current node, so you wont see voltage there. Check the opamp first in a normal opamp circuit.
You have all the pins available of the transistor in the 726, you can measure that out of circuit with a standard transistor tester.

 

[mkiijam]

Thank you, I was just about to write "duh" as a response to my own query. Current mode! I tested the two transistors with my little Atlas DCA55. Both pairs comeback as diode junctions. Not positive here, but bingo.

I stuck a 2n3904 in there based on a conversation with my chatbot, and replaced the MC1456, still no joy.