Any tips for troubleshooting a DAM meathead clone?

[Redvers]

So I bought a populated board off eBay, took some caps off and made them switchable, added a 3pdt switch with daughterboard, led, jacks etc. It's not working. Led lights up, very quiet clean signal when active, volume pot clearly working as intended.

Any ideas about where to start troubleshooting? Transistor voltages etc? Just to check this isn't a positive ground fuzz is it?

[Plexi]

You should check for the transistors pinout and of course: bias.
It's very delicated in this design.

[Redvers]

Ahh there's some continuity issues on my little cap board. If I touch both legs of a cap should a signal tester always pick it up?

[duck_arse]

1) circuit diagram [yes, I know, it's probably a fuzzface].
2) circuit voltages.
3) photos of the offending article.

I think there is a sticky page somewhere, outlines these steps.