Wrighty

I've got a 3600VZ on the bench here, with an odd fault on one channel. Basically, it looks like something's going unstable and oscillating in the positive half of the cycle, resulting in this output waveform (photos were taken a while ago):

With no load attached:


With 4 ohm dummy load attached:


I happen to be using a 200Hz sine wave input, but some kind of distortion happens at all frequencies. The trace is shifted down, so the oscillation can be seen on the positive cycle.

Here are some more photos from today, with no load, at different frequencies:

100Hz:


1500Hz:


10000Hz:


Any ideas?? Note the huge negative spike at the same positive voltage level on every trace... Biases are all in spec and I've swapped everything socketed on the main board to no avail.

Cheers,

Richard