Hughes & Kettner ATTAX 100 effects fail

[H&KUSER]

i've recently bought a second hand H&K ATTAX 100 head.
Its the base model single input, 4 channel, non-midi unit.
I've used it once, it produced a high pitch hum (feedback like), but now it screeches and howls like a radio having a static fit.
I've narrowed the problem down to the effects processor and after disconnecting the module, it stopped, but i lose channel selection, it also has a cycling click (most likely incomplete circuit).
i've contacted the importer and requested assistance, waiting for reply, any suggestions or anybody encountered similar probs?

[Jazz P Bass]

Check the power supply for the processor (5Volts?)
If there is a separate supply, replace it's filter capacitor.
I went through this on a H&K Matrix 100.
The cap was bad.
The voltage rating was a tad low so I upped it.