The printed circuit board has probably failed, this model was featured somtime ago on a BBC Watchdog program, as a really bad buy and for sometime Potterton were embarrased enough to replace them for free. However the replacement PCB now costs over one hundred pounds. If your handy with a soldering iron, the joints on the rear of the PCB can be resoldered, but it's not a job for an amateur and you've got to know what you're looking for.
Probably best to buy a new PCB but this now incorporates the whole wiring loom and a lot of work.
Bite the bullet, get a professional and be warm for Xmas.
Combi Cure, Liverpool
December 2009