by crochambeau » Wed Mar 13, 2019 12:13 am
I think everyone else has you well covered here, but I'll throw in as well anyway.
Is it safe to say you haven't purchased an o-scope yet? Those are my debugging tool of choice, but we'll ignore that for now.
My method is visual first pass. I want to admire all the joints/etc. involved. Back lighting the circuit is helpful to spot shorts.
DC measurements throughout can root out problem areas, be it a sort, and open, or mismanaged bias.
I find it beneficial to make a game out of troubleshooting, or at the very least involve myself when my mind is relatively fresh and open to information. It's a benefit of experience that you may have a shopping list of plausible faults in mind when approaching such a problem, but it's far more important to let the circuit speak to you if you want to source the issue (that is to say, don't talk over the circuit, or ignore evidence while fixated on your suspicion). Circuits are often mute though, so you have to find ways to speak for them - it can be a zen like catch 22.
Oblique mysticism aside, I'm trying to say you're better off avoiding certain mindsets while investigating. I think that's the biggest tool.
An audio probe is just a DC blocking capacitor (avoid polarized caps) connected to an audio jack/amplifier somehow. I like the scope because I can watch the DC level as well as the signal, but you can get that information without the expensive thing on the bench.