Hi, this issue could be caused by a number of things from simple dirty connections internally to multiple component failure.

I am unaware of your competency level so am reluctant to advise component diagnosis given the potentially lethal voltages that you may encounter.

I would recommend a third party repair company take a look at it but new spares are pretty hard to source as are second user spares, so prepare yourself for it to be beyond economical repair.

Where abouts are you based?