Cyrus 2 hum

[sippy]

Soooo,
bout a year ago the chance came up to buy Cyrus 2 and PSX, a combo i aspired to when starting my hifi........oddesy.
40 pounds and two old wetsuits (sponsorship for my surfings great, cheap suits ect) worth the same for the above.
ive been using this combo for about 5 months now, absolutly no problems with the attenuator or selector sitches, only case work paint lets things down - their going black. A few days ago i must of had a power surge and blew up my linux computer, the amp is generaly left plugged in but wasnt as i was fighting mains leads, only the input lead from the comp was plugged in to the C2.
So i thought nothing of it apart from being mildly miffed about looseing a computer, plugged the amp back together, switched on and enjoyed till late.....
Turned it off, vol at zero, select mute, psx power off, C2 off, put kettle on and theres a hum from the left channel.
Next day i fired it up and the same thing at switchdown, the hum starts about 10 - 15 secs after switching it off and lasts about 20 secs.
It plays just fine, nothing untoward going on.
Ive read the one major thread on cyrus amps i could find but nothing in there is remotely like this problem, though general concensus is to change the electrolitic caps and maybe a resistor or two - not something thats beyond me, maybe a little daunting after a long long break frm diy'ing but doable.
So, any wild guesses as to what the problem might be?

[singa]

Hi,The power filter caps will start to discharge after power is switched off,
so it's likely the power amp circuit will be partially powered and therefore if
there is hum it will be amplified untill the caps drained off to a significant level
too low to power the circuit.

Implying that there was no hum when normally power but only during switch off may indicate there is a ground loop created and lower resistance somewhere in the circuit.Prehaps the power surge did "something" to the amp.
Try checking the input cable and other wires for fray ends that touches the
gnd return part of the connector or a good cleaning of the connectors and
dust in the amps.

[sippy]

Thanks for the reply singa
Ive looked inside for the second time since buying, without removeing the amps pcb to check for overheated traces, nothing looks out of the ordinary. As everything was unplugged from the mains, i took the opportunity to change the speaker cables which required makeing sure the bare ends were hidden - even though they were,a wrap of insulateing tape makes double sure!
I guess its time to dig out the 3rd string amp and my DMM..........and get a new battery for it.