Hey Guys, Might not be the right forum here but anyway. I have recently being having problems with my Randall RX120DHS Amp. when I have it up to high volumes it cuts out and starts a loud buzz that doesn't stop even if I turn down the master volume, Or the volume on my guitar. If I put my ear real close to the amp I can slightly hear my guitar in the background of the loud buzz. The other strange thing is if I turn it off and turn it back on it stops for maybe another 5 mins or so then continues to buzz (I know thats very unhealthy for the amp). I can play for hours on low volume and have no problems. Ive heard it could have something to do with the outlet Im using, it is most defiantly not my leads as I recently purchased all new leads, Or could my analog pedals im using possibly be damaged? If anyone has any information regarding this it would be much appreciated.

If it depends on the amp's volume, it's probably not the pedals. If it only happens when you turn it up loud, it's probably one particular stage that's got a messed up transistor or something. There's really no way to know unless you poke around with a multi-meter though. But I'm not an amp tech, so I could be/probably am completely wrong haha.
If it depends on the volume of your amp, it's most likely a power amp issue; without any other info I'd say either the power supply caps are bad or, more likely, you have a power transistor failure. If you don't have experience working inside of amps, I recommend taking it to a tech, safety is worth A LOT more than money.

But, if you do want to poke around, you'll need a multimeter and a pair of hands and eyes. Look for any electrolytic caps that are bulged, burnt, or cracked, look for burnt or cracked components including the power transistors. If it's bad enough, there will be burn marks on the PCB.
hey mate, thanks for the reply. yeah Ive taken a peek inside, I don't have a multi-meter so couldnt check that side of things.. but every seems to be fine couldnt find any damage to transistors, capacitors or burn marks on the pcb etc.. any other ideas??
The only place it seems to be happening is at a certain house I jam in as well (reasonably old). Is there any chance old unshielded wires/circuits could effect an amp this much??