Today my neighbor came over to jam and brought an electronic pedal  arena 2000. I noticed the guitar volume was much higher than it should be as I had the volume on input 1 all the way down. We unplugged the pedal and found the amp volume would go up and then down as we played, we plugged a guitar into input 2 and found that both guitars would ramp up and then down.

the amp is 15 years old and doesn't get much play as it's a bit too much for the small room (realistically it may have 100 hours total at lower volumes), it has been parked in same spot all this time.

any help would be appreciated 

Frank in Florida