Sunn concert amp, distortion does not work

[Desman]

So I just bought a sunn concert guitar amp off ebay, the seller said he had no problems with the distortion before so it must have broke during shipping. Everything works fine except for the distortion. I took the casing off to see if it was an obvious problem but everything looked to be fine and in place, so I'm not sure what to do. Should I just take it to a repair guy or is this an easy repair for myself?

[drewl]

you need a footswitch or shorting jack connected to the rca jack on the rear panel of the amp to turn it on.
It doesn't sound too bad, not too good either.