Hairball Audio said:Try the signal generator. That will tell us a lot.
Ok, I'm not positive I set this up properly (I pumped 1khz into a signal tracer, read 100mv across the two leads, clipped them together and touched the probe to TP1) , but that gave me 153mv at TP15. Please let me know if there's a better way to run this test, I have an oscillator on my console and also in a DAW (obviously) that I've been running to the XLR of the 500 series rack.
I couldn't think of a better way to inject the signal and have another hand free to test the test point.