e-licktronic Forum

Every other voice sounds good.

I did the original service manual mod in the Noise section. I'm wondering if that affected the Low Tom.

I have resoldered every point in the Low Tom section. I've replaced the 4558C and the 1N60P diodes.

I see normal voltage on pads of 4558C.

I'm having trouble searching the forum for answers, because the search system doesn't allow simple searches for "Low Tom" combined with other simple words.

If anyone has any ideas, I'm all ears! I am dying to finish this and actually use it on some tracks.

I did the original service manual mod in the Noise section. I'm wondering if that affected the Low Tom.

I don't think so because the Mid and Hi Tom's are still okay...

I have resoldered every point in the Low Tom section. I've replaced the 4558C and the 1N60P diodes.

I see normal voltage on pads of 4558C.

It's difficult to say what's wrong when a circuit doesn't work and in this case doesn't produce a sound at all...

Does the Low Conga produce any sound?


Maybe it's time to build a simple audioprobe (if you don't have a Scope) and start probing the circuit
to find the cause.


The lucky part is that you have 2 almost identical circuits that work properly so i would print out the schematics
and start measuring with your DMM and audioprobe. Sometimes you can pull it of with just a headphone, probe the circuit with the tip and connect the sleeve from your jack to ground and fiddle thru the circuit.

http://www.diystompboxes.com/pedals/debug.html

When you say every other voice works, does that include the Low Conga? If so it means the trigger works and the problem lies only in the tom circuit.

Either way, some places to look at are Q50,51&52 and U13 if you replaced U15.

There is no Low Conga sounding either. The Snare, Mid Tom, and High Tom all sound good.

Any idea what voltages and/or waveforms I should be seeing at Q50, 51, and 52?

I replaced U13. Problem is still present.

Oh, and. . . you're my hero—the case is AMAZING!

ElSchtroumpf wrote:When you say every other voice works, does that include the Low Conga? If so it means the trigger works and the problem lies only in the tom circuit.

Either way, some places to look at are Q50,51&52 and U13 if you replaced U15.

If possible, try replacing Q50 and Q51. Also check the output section of the voice : the joints on VR10 and the orientation of C82. I'm guessing those would be the prime suspects for not having any sound.

And I'm glad you like it!

Thanks so much for the suggestions. I have an update!

I replaced Q50 and checked that C82 is correctly positioned. I also rechecked the solder points on VR10. I don't have any more 2SA733 trannies.

More importantly, I changed speakers, and the Low Clave DOES sound, but I can only hear it when the tone pot is turned up. The volume is low, but it does sound correctly. The Low Tom makes a tiny bit of sound at the same point on the pot, but it is more like a faint click.

This now seems like an op-amp or resistor problem to me. I am going to go over every resistor value, to make sure that I didn't slip a low-value resistor into the circuit.

If you have any suggestions, please keep them coming—we're so close to solving this thing

ElSchtroumpf wrote:If possible, try replacing Q50 and Q51. Also check the output section of the voice : the joints on VR10 and the orientation of C82. I'm guessing those would be the prime suspects for not having any sound.

And I'm glad you like it!