well, one down, one to go... (by the way - we're talking about a neotek series 1e channel strip here)
i got myself a nice software square wave generator and am feeding the tone in. one behavior that i'm seeing is that when the power is off, i can step through about half of the unit (past the patchbay insert points) tracing the signal, but it gets lost before the direct out.
when i power up though - when i put the probe on the pcb, the line jumps wayyyyy off the screen and very slowly comes back down to where i can see it. the peak light is constantly lit up, and i'm sure there's some oscillation going on in there. question: is oscillation a symptom only of faulty ICs? ie, if i were to just go ahead and replace ALL of them, conceivably i would fix the problem? i've already tried replacing the ICs (TL074) that seemed suspect (not the EQ chips though) - as well as the FETS that buffer the first IC the signal hits. (as initially suspected by my friend - though it hasn't fixed the problem)
could anyone suggest some high-level troubleshooting techniques here? i basically get that the process is to stick a tone in - and try and trace it though the schematic until i find where it breaks down, but what am i looking for? what's the expected behavior after say, a resistor or capacitor? also, [dummy question stating the obvious] for meaningful results i need power on while doing this - isn't that going to further damage whatever is broken the more i poke around with the power on?
any suggestions for my novice fumbling self would be greatly appreciated.
thanks so much!
-nick