[SOLVED] Need help to troubleshoot Bass Drum

Hey everyone!

A few weeks ago I decided it would be a nice idea to apply the fix for the Bass Drum Buzz (trace was too close to ground plane so, as advised, I replaced the trace with a wire on the component side). After the fix, the BD was not working at all, so I must have broken something in the process (it was a messy desoldering process).

At first I thought I must have damaged the IC11 OPAMP while desoldering it so I replaced it with a new one, but still no luck (in the process I put a socket for IC11). So now I'm left with a broken BD which is horrible. Since I have a USB scope I measured all the labelled points on the silkscreen and here are the results:

[*]TRIG: OK got a correct trig
[*]PULSE: OK got a pulse waveform
[*]ENV3: OK got an envelope
[*]VCO: OK got a saw wave
[*]Noise: OK got noise I think (SD works anyway)
[*]ENV1: 0V I think
[*]ENV2: constant -10.4V
[*]ACC: constant -13.75V

As you can see, there is something wrong with ENV1, ENV2 and ACC I suppose? I have no idea what they should behave like since I'm no electrical or electronics engineer (although I'm a materials engineer).

Would someone be able to narrow down the problematic area knowing this? I can measure more points if you tell me where.

I think I accidentally triggered a bass drum sound while probing with my scope by touching one of the pins (I had the nava hooked up to my speakers) but I was not able to reproduce, but it's encouraging knowing it can produce some kind of sound in the bass drum section.

THANKS!

Bumping this to the top

Finally! With no other idea and/or choice, I finally took the time to check for continuity in the whole kick drum section. I tested all the traces and found the culprit! Don't mind the flux residues

[resize=400]http://i.imgur.com/5tF5MMJ.jpg[/resize] [resize=400]http://i.imgur.com/xz81Bmi.jpg[/resize]

Just for my learning, which part turned out to be the problem? Hopefully you were able to get it fixed ok!

PortableFishy wrote:Just for my learning, which part turned out to be the problem? Hopefully you were able to get it fixed ok!

Look at the black wire. He had a broken trace between those two points and fixed it with that wire.

KlangGenerator wrote:
PortableFishy wrote:Just for my learning, which part turned out to be the problem? Hopefully you were able to get it fixed ok!
Look at the black wire. He had a broken trace between those two points and fixed it with that wire.

Thanks KlangGenerator! Are broken traces on the PCB common or does this usually only happen when we accidentally damage it while working on it?

PortableFishy wrote: Thanks KlangGenerator! Are broken traces on the PCB common or does this usually only happen when we accidentally damage it while working on it?

I've seen several people reporting broken traces in the forum, and that's actually what gave me the idea to check for continuity. So yes, I think it could well happen, but in my case it's probably because I desoldered the IC in that region in order to fix the bass drum buzz. (the pads come off easily if you are inexperienced like me).

Additional note: I was able to remove the ground planes from the layers PDF files with the help of Illustrator and the magic wand tool. Setting it to match stroke width and stroke color with a tolerance of 0, clicking on one of the ground plane strokes allowed me to select all of them at once, and then delete them. It's much easier to see what's going on without the ground planes. I then superimposed both layers in photoshop and made the silkscreen info less visible, and also adjusted the traces colors to make them lighter (better contrast with my black sharpie)