Renown 400 Nasty Noise

[kn6xu]

Hello All. Glad I found this board. Lots of good info here! Now for my issue....
I picked up an '87 PV Renown 400 and the first day I hooked it up and played thru it it was great. The 2nd day I started using it again and about 2 hours into a great jam the darn thing cut out and started producing this nasty loud buzz and stopped producing output from the guitar. At first I thought maybe a bad cord so while this noise was rearing it's ugly head I disconnected the guitar cord and the noise was still there. I even disconnected the stock foot switch and the noise was still there. No other devices were connected and none of the controls had any effect. Finally in desperation I gave the thing a whack on top just above the on/off and ground switches and it went away. I pluged my axe back in and continued playing then a few minutes later it happened again. I'm hoping this is just something loose but I've never taken one of these apart before so I thought some input from you folks might be helpful. Any suggestions as well as do's and dont's would sure be appreciated.
Thanks,
Paul

[teemuk]

Well, it's obviously falling apart. My guess is that there's a broken solder joint somewhere that goes open after the amp warms up. Whacking the thing can fix it temporarily but eventually even that won't help. Is that nasty buzz something like 50/100 Hz hum? If yes, then likely it's a filter cap or something related getting loose somewhere. If you are confident working with this sort of stuff then pull the thing apart, feed continuous signal through the amp and start tapping the components lightly. Don't just "hammer" the whole thing. Advance in logical order so that you can pinpoint the fault to a small area. Likely you will find the component that is getting loose pretty fast. But be cautious not to short anything or get electrocuted! You could also try warming up components or using cold spray on them - or just simply inspect the condition of solder joints with a magnifier. Once you have pinpointed the faulty solder joint just redo the solder. If this is over your head take the amp to service before you do turn a small problem into a bigger one.

[kn6xu]

Yeah teemuk the problem was obvious once I opened her up. This amp has had this problem for a while it seems. Instead of fixing the problem properly the previous owner decided to "tighten up" the filter caps by jamming a folded up piece of paper between them. I pulled the paper wedge and one of them started flopping around like a rag doll. I went ahead and re-soldered the caps and hit all the other joints I could get to, put her back together and now she's pumping out beautiful clean sound once again. Thanks for the input!