So, I boxed this over the weekend and it seemed to stop working: low volume, and a lot of feedback with the sustain pot at 25% or more. Ended up rebuilding it, and now it seems to be passing clean signal with the effected signal: still getting a lot of feedback with the sustain pot turned up. Checked for bridges/verified my board against the layout and it's a match. Waiting on a new Peak Meter to verify the gains/pinouts of the transistors, but I did verify all other components are good, so not sure about this one.
Found the issue. it was missing a cut which should be below 1M resistor at the bottom of the layout. No wonder you got squealing since since the signal was fed from the tone pot to the input stage.
Brilliant! That did the trick. Thick and fuzzy with 2N5133s for Q1-3. Going to try some higher gain combos in there, see what happens (CS1504, ME4003, other 2Ns) but this should be a keeper.
Question: Layout says "Q1-3:2N5133, Q2: BC109C" - should that be Q4?
ReplyDeleteYes. BC 109C should be Q4.
DeleteMark it verified - sounds pretty good - definitely less aggressive than the P19, but solid.
ReplyDeleteThanks Craig! Tagged.
DeleteSo, I boxed this over the weekend and it seemed to stop working: low volume, and a lot of feedback with the sustain pot at 25% or more. Ended up rebuilding it, and now it seems to be passing clean signal with the effected signal: still getting a lot of feedback with the sustain pot turned up. Checked for bridges/verified my board against the layout and it's a match. Waiting on a new Peak Meter to verify the gains/pinouts of the transistors, but I did verify all other components are good, so not sure about this one.
ReplyDeleteFound the issue. it was missing a cut which should be below 1M resistor at the bottom of the layout. No wonder you got squealing since since the signal was fed from the tone pot to the input stage.
DeleteBrilliant! That did the trick. Thick and fuzzy with 2N5133s for Q1-3. Going to try some higher gain combos in there, see what happens (CS1504, ME4003, other 2Ns) but this should be a keeper.
DeleteGreat! Glad you got it working!. I haven't tried 2N5133s in a big muff yet but my favorite so far ME4003's.
DeleteI just received 100 from the U.K. off eBay, so those are queued up first for testing.
Delete