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Fried input on doepfer mixer?
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Fried input on doepfer mixer?
Knobtwister
I bought a doepfer mixer, 138b, last month and I just noticed that input #3 seems to have stopped working. When i plug in something to it, the sound is extremely low and there's almost no gain when I turn the knob. All other inputs work fine. Anyone got a clue? very frustrating
phono1337
sounds like the quad opamp has a bad channel, iirc its an LM324N which you can get at most component stores, very cheap, its probably socketed too on the mixer, so buy, pull and replace wink

http://www.electrokit.se/ic-linjara-lm324n-dil14-quad-op-amp_40350003
Tim Stinchcombe
If it is just one channel, then I doubt it is the chip - all channels go through both op amps in the chip, so if it is still OK for the other channels, I would suspect some sort of break in the signal somewhere. Could be the jack socket isn't making contact properly, or there is some sort of break in a track (check around the pot terminals, especially the middle one, for that channel), or it might be a 'bad joint', which can be pretty hard to find, even for the trained eye! If you have some sort of continuity tester, you could check point-to-point by following the tracks for that channel.

Tim
Knobtwister
Thanks for the tip mate. I'll check with the store first and if they're willing to pay for the shipment for repair I'll send it to them, otherwise I'll do my best with my limited electric knowledge MY ASS IS BLEEDING
Knobtwister
I just checked around the pots and on the pcb and everything looks to be in order, will investigate further tomorrow. Thanks for helping me out, I love this forum love
Knobtwister
Just a thought; is there any possibility that the module could be damaged by mixing CVsignals instead of audio? I just find it weird that it just stopped working so suddenly... hmmm.....
Tim Stinchcombe
Knobtwister wrote:
Just a thought; is there any possibility that the module could be damaged by mixing CVsignals instead of audio? I just find it weird that it just stopped working so suddenly... hmmm.....
No, in normal use it is equally at home with both DC and slow moving control voltages, and audio rate signals. That it stopped working suddenly still sounds to me like a broken track, but if you don't have a continuity tester, and with little electronics experience, finding it could be very difficult!

Tim
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