Hi all. I have a weird problem for the electronics gurus on here. I have a second-hand Fender 112SE amp that gives me what sounds like a ground hum.

With nothing plugged in and the amp turned on, it's completely silent. The hum starts when I plug a cord into one of the input jacks. The hum stays the same whether I'm plugged into jack 1 or 2, and doesn't change at all when I turn up the volume. The hum is also the same when the other end of the cord is plugged in to a guitar and when it's not (this is with the amp's volume at zero). The hum is also (strangely) slightly quieter on the amp's drive channel. I've tried different cords, guitars, and outlets in my house, and the hum is still there. Besides the hum, the amp works perfectly and sounds great.

Anyone have any ideas? Thanks in advance for the input.
To know death, you have to f*ck life in the gallbladder...
Hi yadfather. Sorry about that. I (obviously) haven't logged in in a while.

Anyway, for what it's worth, the problem seems to have been that something associated with the reverb on the amp somehow got fried without it affecting anything else. With the reverb knob up, I get the hum and no 'verb, but with the knob at 0, the hum goes away.

Hope that helps at all.
To know death, you have to f*ck life in the gallbladder...
It could also be if you are using an EU spec. amp in the UK as they aren't made specifically for 240 Volts.