Audio Systems: Old Power Amp, power amp, audio cables

Question
I have a very old power amp and when it is hooked up with the audio cables intact it gives off a blast of sound every so often. I was looking at the meters on the front and they kept going up and down to the 240 watt mark, also the protection light never goes out now and it used to after about 5 seconds of being turned on. When I take the audio cords out of the power amp I hear a clicking sound and it is timed with the blast of sound that comes out when the audio cords are hooked up to the amp.

Answer
first i would use some good contact cleaner such as de-ox-id on all switches and controls. next, examine solder side of all boards, i'm sure you'll find many that desperately need resoldering. then fire it up and see if condition changes at all or disappears.