DOD 250, driving me crazy

[artifus]

Given that all of the wiring is stuffed in heat shrink and is all the same color. How can you tell that each wire is going to the right place on its other end?

continuity? (multimeter).

[tubelectron]

Do not bother with heatshrink :



Check your PCB with a magnifier : mine had a microscopic unwanted contact between traces causing pin 3 to pin 6 short-circuit, silencing the 741. But maybe you have a younger (and so better) sight than me...

Also, what is a good start when debugging these sort of problems? Are my layout and schematic all right at least?

Troubleshooting is an art which has to be learned by experience...

The good start is to suspect everything - even what you think is good or foolproof : it MUST be confirmed, no divination here, or you will turn around...

Check you schem from the completed PCB directly : trace the schematic - accurately, again no supposition, using a VTVM for confirmation - and re-draw it on a paper. After that, compare with the theorical schem : is it the same ? Where are the differences ? Re-check if needed !

Make voltage measurements, components measurement, cross-check the results...

Make signal-tracing : inject 50mV AC sine wave at 400Hz at the input, connect an amp at the out (clean mode, moderate volume), and use a scope to trace the signal, or if you have it, an audio signal tracer (you can't imagine how useful this neglected instrument can be !).

This may take time, indeed, because it resembles a step by step operation, but it is the best way to draw the conclusions to find the culprit. The DOD250 isn't a very complicated circuit, so you should find quite quickly...

A+!

[FIŠ]

heatshrink is there to make things tidier, i like it that way.
Troubleshooting can be real pain in the ass, I'd rather build same stuff over again or pay someone to fix it, but as you said its all because of an experience