Last month I found a SoundCraftsmen MA5002 amp of unknown condition in the basement of a building my buddy owns,
original thread here. Today I finally went over and picked it up. I got it home and plugged it in unconnected to see what would happen. The "overload" light came on and the VU meter for channel A showed the needle at a steady 20 while the channel B meter didn't move any. Also it started making a steady medium pitched clicking about every two seconds, the sound is similar to flicking your finger against a thick glass bottle. Each time it clicked my lights dimmed so I turned it off and uplugged it. If we can get it working the plan is for my buddy to use at his place.
I'm looking for any advice on how to properly go about testing it, without worrying about damage to any of my other equipment and to find out what is causing the clicking and overload light to come on.