Hi!

*I'm pretty sure my dishwasher has just the one PCB.

Fair enough. I can't view your circuit diagram from where I am now,
but I will look at it as soon as time allows and see if I have any
further thoughts.

*And of course, drinking cups of tea and eating biscuits (cookies?).

That's always a good troubleshooting practice!

*...On the day the dishwasher went wonky, that morning we had
just had our electricity reconnected to the mains grid after a week
of being without electricity.

A-ha!

Now that's a good point to consider. When power is first restored,
it's not always stable. The voltage may be high, low or "wobbly".
That's hard on electrical equipment.

Since you mentioned a lightbulb failing and the line voltage being at
255 volts (instead of the more normal 240), it is obvious that your
line voltage was high. This puts stress on everything that is plugged
in and operating at the time. Simpler devices are likely to take it
better, at least to a point. (Had your lightbulb survived, it would
have been a good example of this theory.)

I'm afraid that it is likely your dishwasher was damaged and not just
put into a confused state. The damage probably took place within a few
minutes.

Since you've replaced the controller board, I am in agreement that you
need to check the sensors and actuators that the control board works
with to get the dishes washed. It's very possible that more damage is
lurking in the shadows.

One must consider that the power supply in the dishwasher may not have
been able to maintain proper voltage regulation, causing high or
incorrect voltages to be present in the unit. This could lead to
damaged sensors, solenoids or whatever else there is in the unit.
Careful testing of each part should be performed--hopefully the
schematic you have shows appropriate characteristics for each part.
Otherwise you will have to make some educated guesses and careful
examinations.

I'll try to get a look at the schematic you have posted and see if
that gives me any ideas.

William