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T Bagger no distortion

Started by jcuempire, March 30, 2011, 02:00:24 PM

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jcuempire

What does it mean when you turn a distortion on and you get the dry signal?  The volume works and 100% brings it to unity gain, but no effect at all.  I did some initial audio probing without success since the signal is coming through the circuit, just not being "effected" by it.  So I guess my question is how does the unit distort?  Is it the IC or the diode?  And if either or both of those components are dead, can the signal still go through?  Or is it, as I suspect, some other weirdness.  I have burned this unit once already.  Literally, smaoke coming out.  The 4001 diode was toasted and replaced.  Anyway, where would you start looking? 

Thanks

madbean

If the 1N4001 is smoking then you have one of three problems: the diode is backwards, the power supply is -9v instead of +9v or there is a solder bridge somewhere connecting the 9v supply trace on the board to ground. Assuming it's not #1 or #2, then you should go back an remelt the solder on the board, and check it under a magnifying glass. If you see any suspect areas between traces, scrape them with an Xacto knife of small flat head screwdriver.

You should also take some voltage readings on your IC after doing all that. You should get about 4.5v on pins 1, 2, 5, 6 and 7, 0v on pin 4, 9v on pin8, and something around 3v on pin3. Any one of these that is significantly off is an indicator of an additional problem.

jcuempire

I will check the voltages on the IC tonight.  The problem was a solder bridge to ground which is fixed.  It snapped the diode in half.  Believe me, I had a huge headache constantly looking at the board with a magnifying glass.  I replaced the 1N4001 ( I bought 50 of them, figure they'll come in handy) and now that's okay.  We'll see what I get.  Thanks

jcuempire

Okay.  All the IC pins check out except 3 & 5.  3 is supposed to ~3 and it's 4.6 and 5 is supposed to be 4.5 and it's 2.6.  It's like they are reversed.