Thanks James,
The problem is fixed - I attached my multimeter to measure the voltage across the on switch and as I turned the power on at the wall, the machine came on and stayed on and now seems to be fully functional again!
I can't be sure if it was connecting the multimeter that fixed it or one of the following:
- Measuring the voltage across all diodes (using the multimeter diode setting).
- Measuring the voltage from base-to-source and base-to-collector on all transistors (using the diode setting).
- Measuring the source-to-collector resistance on all transistors.
- Allowing enough time to pass for something to dry out (although there was no evidence of water).
- General movement of cables if there is a broken one (including taking out the motor control board to check the fuse).
Now when I turn it on at the wall, it doesn't light up until the on button is used.