Serious advice, don't go messing around with electrical gear unless you really know what you're doing (sounds like you don't! :p )
I have had similar problems with amps and poweramps over the years, nothing was ever too expensive to get repaired. Go to the local guitar shop and ask for a list of guys who do amp repairs. Most shops don't do repairs because of the size of the stock, poor return and hassles involved so they refer on to single operators. I found a licenced repairman who did me a great deal and I've used him ever since - he has literally saved me thousands in replacing gear that the shops wouldnt touch.