Bosch SGS69A02GB/13 as good as dead

My Bosch DW Logixx SGS69A02GB/13 has stopped working – symptoms are:

Power on – Display shows normal finish time.
Then after about 3 seconds the display goes blank and nothing works.

Power off and on again – same symptoms, but less than a second to fail.

My suspicion is the control board, but at £120 would be an expensive guess if I’m wrong.

As I’m an electronic design engineer, I’ve done some investigation – my guess is that the board has gone into some form of psu shutdown – possibly to protect itself. So my question was – is it a fault in the board or external.
Without any schematics to help, I’ve had to resort to guesswork

A visual inspection of the control board shows no components visually damaged, but there is a slight burning of the pcb around the pads on a diode – the diode is part of the switch-mode psu circuit, but without schematics I can’t work out what’s happening.

I then disconnected as many of the external plugs to leave just the power connected to the board – on power-up the display shows “126” which I assume is an error code, but again the whole thing goes blank in 3 seconds. Plug back the motor connections and the board acts exactly as before. So this might indicate that there is no external fault as the symptoms don’t really change.

So my questions are:
– Has anyone come across this problem before?
– Are there any other diagnostic actions I can take to narrow down the issue?
– If I replace the control board, are there any set-up procedures I have to go through?
– Are there any test modes I can invoke via the selection buttons?

Thanks

Antony