Thunderstormed Routerboard Mikrotik RB2011UiAS-2HnD-IN

[frenky]

My friend asked me to take a look at router that died during thunderstorm.

Model is RB2011UiAS-2HnD-IN also known as RouterBOARD 2011: http://routerboard.com/RB2011UiAS-2HnD-IN

High resolution img of PCB:  http://img.routerboard.com/mimg/677_hi_res.png

Burned components:



Mosfet on the left is completly shorted to all pins. Two bridge rectifiers have vent holes. This is what I have found so far.

Does anybody know why there are bridge rectifiers inside router?
I wasn't able to find service manual or schematic for this board.

Tnx.

[chris_leyson]

The bridge rectifiers will be for power over ethernet.

[frenky]

Tnx.

It weird that this bridge rectifiers have holes in them but I tested all the diodes inside and could not find anything wrong with it.

[lukaq]

wonder how did it die. Hope you can tell us that

[Monkeh]

wonder how did it die. Hope you can tell us that

It got a few million volts shoved down its throat?

[SeanB]

U903 is likely cooked as well, as it was driving the dead MOSFET. The bridge rectifier will be open circuit on at least one diode, if it let out smoke, or will break down at over a few volts.  If you are lucky the secondary switchers U902 and U1 are not dead as well, if so then both U100 and U400 will be blown, and not easy to replace.

[frenky]

I think I've solved the case but sadly the patient is dead...

Voltage spike first fried the modem. Then it travelled trough POE port into router.
There it fried tiny 85ohm resistor  between sockets and magnetics.
Then it fried both bridge rectifiers and from there the mosfet and both buck converters. (And a few capacitors...)
And from there both main ICs. 

I noticed that both power rails are shorted so I applied 3V 2A to each rail and used thermal camera to find (and remove) all shorted components.
But sadly short circuit on 3.3V rail is still there and the only components heating up are ICs... So no luck I guess...
On this 3.3V rail I also increased the current to 3A but voltage only went up to 2V.