Troubleshooting BMP

[mrsage]

I decided to try taking a step into a larger world by creating my own layout from a schematic, rather than just copying someone else's work. I've done a few simple layouts before, so I felt up to the challenge. Plus, I'm using ExpressPCB, which allows you to link a schematic and a layout. This is really handy, as it lets you run through each of the net connections to make sure that all the bits that are supposed to be connected are, in fact, connected. It also throws up an error message if you're missing an item that should be connected to a particular net.

Anyway, I started with a Big Muff Pi schematic (actually, a Swollen Pickle schem). I built it out, and as I was testing it I noticed that it was having gating issues, which got worse as I turned the Sustain knob down.

When I tested the voltages, I found the following:

9.5 V+

Q1
C =3.55
B = 0.58
E = 0.04

Q2
C= 3.57
B= 0.58
E= 0.04

Q3
C= 0.14
B= 0.62
E= 0.06

Q4
C= 2.87
B= 1.52
E= 0.97


Now, I can see that Q3 is way off, and Q4 seems a bit off, as well. Q1 and Q2 seem a little bit low, but not excessively bad.

The schematic is very close to a standard Big Muff schematic, and I've re-checked it about a dozen or so times against various Big Muff schems I've found. I'm 99% sure that it's correct. I have also re-checked the netlist connections about a half-dozen or so times, and I get no errors or missing connections...which means that the layout is correct according to what the schematic reads.

All my electrolytics are oriented correctly, and all the transistors are, as well. I tried replacing a couple of the caps around the Q3 gain stage, thinking maybe I had a bad component in there. But that didn't have any effect. Double-checked my solder connections, too. Very clean, with no bridges.

I'm not sure what to do next...If the schematic is correct and the layout matches the schematic, then my first inclination would be that I've got a bad component somewhere...but I don't know quite know where to start. Any suggestions?

[deadsnake]

I don't know if this help much. If you a DMM(Digital Multimeter) it could help a lot. I just bought one and I solved most of problems with it. Acctually I was not going to complete without one. Check continuity with it, I found bridges that I couldn't spot myself. Try masking the other components with paper when you solder so this doesn't happen. I don't remember in what post I read this but there was a "general rule" for transistors I don't remember very well but the difference between the base and the collector/emmiter(is one of them, not both) had to be somewhere about 0.6V. Even tough I don't remember, from what I see they aren't quite right.