6 flashes means the MPU is not receiving the 43v solenoid voltage. You can check the voltage is present by measuring it on the rectifier board. If you get 43volts here then the problem could be on either the rectifier board connectors or MPU J4 (in lower hand corner) connector. With a torch have a look at all the pins in J4 for any green corrosion and also look into the connector holes with a torch held behind the connector. It's difficult but you can sometimes see a connector which does not have enough tension to make full contact or has broken inside the connector housing.
The fuse on the solenoid board is for hv to the display. If the fuse is blown then the displays should not work.
