g3 accenta bell problem?

have g3 accenta and bell started screeching, and power led on keypad now flashing.
sounder screeching is panel generated - not cable damage and happens with only supply to sounder. with tamper open red led ok but when tamper closed screeching?
power led on keypad thought was service timer but unable to rectify?
has anyone else had this issue?

chris blackmore
December 2014