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Befaco Rampage Ch. B does not (really) work
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Befaco Rampage Ch. B does not (really) work
Hello everyone,

I'm in the need for some helping opinions. I have built a Befaco Rampage about 2 months ago (self-sourced parts), but when powered on, Channel B was not working. I had one, long trouble-shooting session some time ago with no results, but before I go further I'd like to ask for some help.

The Symptoms:

When triggered, the Rise portion works as it should, however when it reaches the Fall stage, the OUT B signal stays high (at the peak) indefinitely or until the system is powered off. The cycle is definitely in the Fall stage as it also outputs a gate at the Falling output.

Another strange symptom is that sometimes Ch. B outputs a constant Falling gate, without ever being triggered. In this case there's of course nothing at OUT B. This always happens when the shortest Range is selected, and is the case when the Fall slider is low enough for the two other ranges. If the Fall time is increased sufficiently the gate output vanishes

I think everything works other than this (but I couldn't check Cycle B and In B obviously).

What I've done so far:

First I inspected all the joints, polarities, other "visible stuff" but everything looked fine. If one was suspicious I retouched that (I've actually done this a few times including during the build).

Since Channel A works perfectly, I swapped the ICs from the two sides, resulting in no improvement whatsoever.

Then I started checking continuity. In the first picture I highlighted the area that I definitely checked, but there were other joints checked, at Ch A, the control boards etc. But I'm quite sure the problem is on the Main Board.

I have a feeling that the culprit is gonna be a resistor or something but I would appreciate any input on this problem! help

Here are some picture, including the schematic:

I wanted to upload more pics but the service just died or something.
Also when bracketing the schematics with the red lines, I realised that the problem might be in the CV summing and shape feedback bit which I have not checked at all. Anyway, please help!
I had a similar experience, chanel B failing too. I just reflowed the whole B section and VOILA!, it works.

It will only take like 5/7 mins. I would start there. If that not works, then go for the logic puzzle of finding the resistor or cap
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