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Doepfer module repair- usa
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Doepfer module repair- usa
Jeff242
Does anyone know where or who does repair on doepfer modules in the United States?

Jeff
acgenerator
*MOST* of the Doepfer modules are generally straight-forward for service as they are thru-hole components and basic analog circuits.

Which module is it? what is wrong? You may be able to get guidance from someone here.
Jeff242
acgenerator wrote:
*MOST* of the Doepfer modules are generally straight-forward for service as they are thru-hole components and basic analog circuits.

Which module is it? what is wrong? You may be able to get guidance from someone here.


Hahahahaha, that’s what I was told before. I bought a 20$ soldering iron from that hardware store thinking how hard can this be. What a disaster! I had no clue what I was doing.

I have a high end vco with a non-working pw knob (pulse circuit itself is fine, I just can’t offset the pulse width from the front panel)

Also have a distortion/wave shaper with a resistor that has a broken wire on one side
Rigo
Jeff242 wrote:
Also have a distortion/wave shaper with a resistor that has a broken wire on one side

This could be a deliberate modification, at least if you bought it second hand:

http://www.doepfer.de/DIY/a100_diy.htm#A136%20Modification
acgenerator
Jeff242 wrote:
I had no clue what I was doing.


that's everyone at the beginning

Jeff242 wrote:

I have a high end vco with a non-working pw knob (pulse circuit itself is fine, I just can’t offset the pulse width from the front panel)

Also have a distortion/wave shaper with a resistor that has a broken wire on one side


for the High-end VCO (assumed A111-1 or A111-2) the PW function there are two controls PW knob (which works with out CV) and PCV which attenuates the CV jack. The Range of the PW value is 0% of the wave to 100% so with some voltages you may need to adjust both knobs to hear the effect especially if you are using the very extreme octaves. If you have a module with a scope, it'll help you see your adjustments as you make them.

If this isn't a matter of tuning / usage, the first thing I'd look at is ensuring the Potentiometer is well soldered to the PCB and not loose or has a broken trace line on the board. Does it wobble? it may just need to have it's solder reheated to fix the connection. A picture would help here. You may also have a bad Potentiometer. You can use a multimeter with the power off to determine if it have proper resistance values. It will have it's expected value printed/stamped on it.

Additionally on some early Doepfer modules, the metal tabs on jacks occasionally need to be pushed in tighter with a screwdriver to have a more solid contact.

for the distortion/wave shaper assumed A-136 , if the wire itself is cut the solution is to desolder the old resister and replace with a new one of the same value. If the trace on the board is actually cut / scratched out lines, you'd have to solder a small piece of wire in it's place. My assumption here is there this resistor is not burnt up / charred / etc which would likely indicate it having plugged it the rough way and the resistor was used like a fuse to protect the rest of the circuit. Again pictures would help.

The great news is both of these would be analog modules and wouldn't require specialty parts or flashing code to repair.
acgenerator
Jeff242 wrote:
I bought a 20$ soldering iron from that hardware store


as a side note, soldering irons and the solder from the hardware store are generally not suitable for electronics. You should get a temperature adjustable iron from a place like Microcenter or an electronics parts store to due this work. Additionally you need solder made for electronics not lead pipes. "Flux" is also a good idea to ensure a good connection. You can also get desolder wick/braid or a desolder pump fromt he same store for removing parts.

I'd start with going to a Makerspace event of some sort. They almost always have someone that can teach you how to solder.
Shledge
Soldering isn't difficult, even with a cheapo soldering iron. I've fixed gear before by simply reflowing the solder that was already there.
Jeff242
This is what Doepfer had to say when I emailed them about the distortion Waveshaper unit.

“Hello,

R2 defines the amplification of the internal pre-amplifier. If it broken the
pre-amplifier does no longer "amplify" (i.e. amplification = 1). Normally
that's no problem if the incoming signal has sufficient level.
Only if the module does not work as it should with low level signals R2
should be replaced.

Best regards
Dieter Doepfer”
Jeff242
Rigo wrote:
Jeff242 wrote:
Also have a distortion/wave shaper with a resistor that has a broken wire on one side

This could be a deliberate modification, at least if you bought it second hand:

http://www.doepfer.de/DIY/a100_diy.htm#A136%20Modification


You are absolutely right. It is this exact modification:
“4.2.2. A-136 Modification: bypassing the internal pre-amplifier
Module A-136 contains an internal pre-amplifier that is used to amplify the input signal by about 3.5 before it is processed by the A-136. Especially for low level audio signals (e.g. output from a VCF) this is useful. But for all signals with a level beyond ~ 7V this causes clipping before the internal processing takes place. Especially for the processing of LFOs or unfiltered VCOs this may cause a problem. To bypass the internal pre-amplifier resistor R2 has to be removed (e.g. by pinching off). R2 is the resistor in the upper third of the pcb which is very close to the rear edge. When R2 is removed the amplification of the internal pre-amplifier becomes "1" (which means that it does no longer amplify).
In addition one has to pay attention that the knob positions may vary a bit from the front panel printing because of mechanical tolerances of the potentiometers and knobs (i.e. "0" is not always exactly the neutral position for "A", "+A" or "-A”


Thank you for pointing this out!
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