[jacobsteel]

I love my KOMA field kit and field kit FX (I got them 2nd hand) but my field kit mixer has a broken channel 1.

I've measured on the board and the working channels (2-3-4) have around 4 V on the center pin of the tone control.
However, the broken / dead / channel (1) measures 6-7 V on the tone control center pin. 

I fear the mixer might be out of warranty - but if anyone here has solved a similar problem I'd be very grateful to hear about it. (I'm thinking along the lines of: if the buffer-amp is broken, possibly you could add an extra LM324 just to handle channel 1 input?)

[chrisi]

If one of your channels in the mixer is broken, it's usually quickest to swap out the LM324s that make up the mixer. It's U1, U2 and U3 in the schematics. I would do it in that order.