Amp Head Gets Power, But No Sound

I have a BH420 amplifier that I use for gigs with a single 18" speaker cab. It suddenly stopped functioning correctly the other day. The power light comes on but there little to no sound that comes from the speaker. The only sound is a very quiet hum ( I have to put my ear next the speaker to hear it). When I turn the amp off there is a quiet "thump" noise but that's all, no signal from the bass guitar. None of the knobs affect the very very low hum. I've tried both inputs, and also tried plugging the speaker in each speaker outputs (there's 2).

Anybody know the issue? How to fix and/or cost of repair?

Also, I know it isn't the bass guitar, speaker, or any cables because I have made sure they're all functional (bass works w other amps, cables are good w other amps, my speaker works w other head etc.)

 

Yes it is! Heavy sucker.

 

Thanks I appreciate it! I took it to a tech today because I'm not experienced at all with repairing amplifiers.