Hi

I recently bought myself a used Line 6 M13. It has a very strange problem. Basically the pedal works fine on occasion, but most of the time, it makes a buzzing noise. All cables, amps, guitars work perfectly, the problem must be in the unit itself.

When i turn it on, all the screens light up and all the buttons/screens work perfectly every time. Now sometimes there is some buzzing right after i turn it on, but it kind of fades away (makes a descending pitched sound until it stops) and the guitar signal passes through cleanly and all the effects/looper/tuner work. But usually this buzzing does not go away and no signal passes through. Also I have found that on the occasions that it does work, it starts to make an overdriven sound when i've played with it for about an hour or so, which gets worse gradually until it's buzzing again, at which point the tuner has stopped working aswell (doesnt respond to playing, only shows a certain note). Signal passes through on bypass mode, all effects turned off.

Ive tried doing a factory reset and plugging into the R input/outputs, or even using the send/return jacks. It's running firmware 2.04

I've given the M13 to the guy that usually fixes my stuff, but he claims the unit works perfectly (he had it for about 2 weeks). He used the same adaptor (Rocktron AC/AC Adaptor, input: 220v-240v 50hz 150mA, output: 9v-2000mA 18VA). I've tried it in several diffrent locations, with different cables, amps and guitars and i see no difference.

Im open to suggestions..