Hiwatt Hi Gain 50

Problem: excessive hum from speaker.
Solution :
Often caused by faulty capacitors not smoothing the rectified ac properly however in this amps case it was something else as well.  In this amp a number of op amps that are used for the effects send and return loop are powered by  a 30v supply.  It’s worth checking this as in ones case it had significant ripple caused by a number of minor components. Unusual because the current draw from the op amps would be minimal.

Fender DSP 90, champion 110 and similar

Nice little budget amps with a range of built in effects.  Seem to suffer from intermittent sound loss and cutting out.   The PCB are plagued with bad joints around ribbon cables, regulator  U10, and although I have not seen it the numerous large resistors and caps.

Also recently saw one making g a terrible humming or buzzing noise.  No signal was coming through at all. Current draw on the amp was about right so quickly able to link to open circuit power supply filter capacitors. Replaced, resoldered and glued into position and amp will be good as gold for another ten years minimum.