Grateful for any help with this one....

I have a fuji 4222 plasma that sometimes refuses to start .. once its going
its fine... but once cold... its touch and go .. the problem is getting
worse.
Once it stops working it leaves the red led constantly flashing which I
believe indicates a PSU problem.
Spoke to Fujitsu who reckoned either main PSU board ( my theory) at £450 or
either of the two sustain boards £900 each and its guess work which one !
Does anyone have experience of this unit or similar for a component level
fix ( I am a qualified HV engineer but don't have any plasma experience)

Really appreciate any help chaps

NEIL