No Output from one of two Mackie MR5 MK2 Monitors

Howdy!

I have a pair of Mackie MR5 MK2s that I bought new over 5 years ago and they have VERY low hours of usage/power-on time.

One of them now only powers on but has no sound/output whatsoever.

Anyone know of a common component failure that I could replace (cap, rectifier, etc) for a repair. I have the schematics but dont know where to start.

Can't afford to send it in for repair, but I am quite skilled with a soldering iron.

Nothing visually shows damage/melting/expansion etc.

Tried all 3 inputs (XLR, 1/4 and RCA). Fuse is fine. LED on.

Been plugged in to a UPS the whole time along with its twin (that is still working fine).

Thanks for any input (on my lack of output)!