I am looking at a car audio amplifier.
I seem to have all the appropriate power rails but am not getting an audio signal through the unit.
In looking at U5 (U5 on board) (U5B on schematic) I get a signal to it, but not from it. I have +12 and -12. R80, R187 and R188 seem close enough to spec.
My scope is acting up so I am sending a 1khz signal in and following it through with an audio tracer. The input side of R18 stays at 1khz. When power is applied, the U5 side of R18 sounds like a capacitor is charging as the unit comes on and then the signal is lost.
Could it be a faulty capacitor around U5? Is U5 faulty? or is something down the line from "radio" back feeding or loading the circuit?
If it were through hole, I would remove and check the capacitors. I am less adept with surface mount.