Guys, need some help....

Bought myself another AV amplifier, this time another Sony model (STR-DB870 - 5.1, digital decoding blah blah)

Thing is, it's perfect in everyway, except one thing - no sound from the front right channel. Now I know it's not the speaker or cable as I tried a different speaker and cable on both the left and right - left works, right doesn't. It's not the inputs either as I tried different ones, and also the internal test tone function, all of which output nothing from the front right.

So I reckon it's dead...

Took the cover off to look inside incase it was bleedingly obvious, but couldn't see anything that looked like it was wrong/missing. The front L+R outputs, along with the 6ch pre outs, are all connected to a daughter PCB. Couldn't see anything wrong on this - two multiplugs connected firmly, the little resistor looking things connected and not broken, etc.... Beneath this PCB was another one with two glass fuse looking things - couldn't get em out, but they looked okay as I could see a filament and no marks to indicate they were broke/burnt out. Again below this PCB was another, also with two glass fuses - same as above, nothing obvious to suggest it's broken.

Looked around but couldn't see any busted terminals or wires, connections, resistor thingys, etc etc...

Any idea's? Advice?