Anyone help me with this? Its an old 4*12 combo which worked fine until
recently when it developed an intermittent click approx every 5
seconds. occasionally upon turning the power on it would just produce a
50Hz hum through the speakers.

Now that is all that it does! Grounds all seem to be fine. pre amp
filter caps, and all power supply components are OK also. There really
isnt that much inside this amp so I can replace it all (apart from the
output transistors which seem to be obsolete), but if anyone has some
time saving ideas I'd be grateful.

Thanks