SS 50 Watt Power Amp Making funny noise When Turned On

[dumbassbob]

I have a Reactive Load Box called a Power Tool,you can plug both a tube preamp and a amp in... I bought in 1993,It has a built in 50 watt power amp,When I first turn it on the On/Off light flickers and it makes a hum...The headphone jack and the "Other" outputs work OK,Any idea what a dumbass should look for? Would a filter cap do that ect... I do not have a schematic..There is No info on the net... It is a cross between a Marshall SE-100 and the one that Groove Tube made..It is 23 yrs old and has worked fine until now...It is way over my head,but thought I would first try here...DAB

[J M Fahey]

I first turn it on the On/Off light flickers and it makes a hum...

Hum as in a single coil or not well shielded guitar or strong LOUD unstoppable hum no guitar sound comes out as in a shorted transistor amp or strong hum but with some guitar sound as in an open filter supply?

Does the speaker cone jump forward or backward and stay there, while humming furiously?

All "hum", all different, pointing to different possible motives.

Measure DC voltage at speaker out terminals.

[dumbassbob]

It is Not a loud hum it does it while I watch the power light switch flicker ,This is when I first turn the Power Tool on,Then about a hour later of playing it started to do it again,But the head phone output did not...I will measure the output jacks..Ok to do with NO load,and do I use DCV?

[TomCarlos]

Bob.... Yes, measure to see if you have any d.c. volts.

[dumbassbob]

Thanks