f12 means a communication error between circuit boards.
Possibly a duff connection on one of the board connectors. Power off, remove covers, disconnect circuit board connectors and clean with toothbrush. May help to tighten them with a pair of pliers. Clean off any corrosion or crud, refit and test.
Check out my site for info: www.2ndwave.co.uk/manual.html
washerman, March 2008
