Have anyone been debugging an APC 5000 VA XLI UPS before?

I have an issue with an older XLI I have no idea how to fix. After a power surge the breaker that runs the APC popped and after that the UPS is absolutely unresponsive (no lights, no fan, nothing). Tried a different battery pack that I know is working and still nothing.

Now im lost. Its no visual damage inside, nor it seems like a fuse on the input side of the UPS (like on the other brands that has that push button).

Anyone that have any clue where the fault might lay?

Attached some photos of how it looks inside of the unit.

 

Did you check, all fuses, input supply and battery fuse ?

Also you can check input brigge rectifier, aux supply.

I had eaton powerware 9130 1000VA model with a faulty dc-dc converter (aux supply 36 to 12V) with same symptoms as your UPS. Problem was blown IRF640 MOSFET.