Help: Aragon 2004 MK II - Powers up but no sound

I have had this amp for a couple years but it has been unused for about a year. I tried to use it this morning and it powers up but there is no sound. I checked the 3 fuses (1 external and 2 internal) and both seems fine. Never the less, I will run to radio shack when they open and replace all 3 fuses.

Does anyone have any idea what could be the problem?

Thanks.