So my friend gave me an amp to fix. As mentioned its the DXB112, a simple 30W combo from crate. 

It turns on, all the lights turn on and the switches react to being pressed but there is no output. I checked for shorts in the input and output and for loose connections. The main power amplifier seemed to be ok. No shorts across certain pins. There is a pop when the amp is turned on and then a pop a few seconds after the power is turned off.

I have some moderate experience with debugging, but am not sure where to take this one.

http://www.crateamps.com/pdf/manuals/DX112212_OM.pdf

Thanks for the help in advance.