More BMP woes.......

[lightningfingers]

I rebuilt my BMP this afternoon, I bought all new parts and everything. And it works, yes but there is the most horrible volume drop, I have to crank the amp up halfway to hear it. The battery is fine it measures ~8.46.
Any ideas what could be causing the lack of output? Other than this problem it sounds very nice.

[zener]

When I built the BMP, I had this problem of delay. It takes 5 or more seconds after hitting the switch for the effect to come in. Also, there were also some moments when the volume will drop and upon shaking the box a bit, it will go back to normal. It turned out to be a loose wiring.

I don't know if this is the same thing happening to you. Is yours in an enclosure already. If yes, have you tested it before putting it in an enclosure.

An audio probe will help you figure out what's wrong. Try to find where in the circuit the volume drops. If it is not in the circuit, then it may probably a loose wiring.

[R.G.]

Any ideas what could be causing the lack of output?

Yes. A lot of them.

The ideas are mostly written down in the Guitar Amp Debugging Page at GEO.  Pretty much every beginner runs into a similar situation, so a long time ago I wrote down a way to systematically look at what might be wrong. That's what became the Debugging Page.

It's hugely likely that there is a wiring error, a soldering problem, or a wrong/incorrect orientation part. The Debugging Page tells you a lot about how to find out what it is. If all that fails, measure the DC voltage on all the transistor pins and report that back here.

[lightningfingers]

great debugging page  and now it works and i'm happy. Thanks everyone who helped :mrgreen:

[Alex C]

Hey, just curious- what turned out to be the problem?

[lightningfingers]

there was a cold solder joint on the emitter of Q4, so it wasnt grounded properly, and all i got was this pathetic little weak fuzz