Try changing the chopper transistor on the H.V. part of the power board, It is a MOSFET type FQPF5N60C. Antistatic precautions must be observed when handling MOFETS. While your changing this you might as well change the capacitor C232 1000uf to a 35 volt type as sugested by Mark DT.This completely cured mine so good look,
R.S.Knight
Richard Knight, January 2015