820-2849 sometimes black screen at startup sometimes starts but crashes

[No-Clean]

Clean board, no liquid.

I tried different RAM one per slot, no battery, SMC and PRAM reset and the symptoms are always the same:

Mac starts up (fan spin) but shows blank screen, this happens more often
Mac starts up chimes, tries to start but crashes and tries again, sometimes it goes straight into above state
Holding the option key does the same as above

There are no lines or weird colors on screen at any time.

 

[2informaticos]

Very likely GPU issue; heat it for test...