An electrolitic cap would heat up fast like that either from reverse polarity, or from overvoltage
Reverse polarity could happen if it is soldered in in reverse, or if some diodes in the rectifier bridge (or single diode for that capacitor in case of a doubler circuit) are shorted and the capacitor is getting AC
Overvoltage in a divider could happen if one side of the load is shorted (due to shorted film capacitor or transistor, ...) and the full voltage falls on the other side. Say if you apply 320V (rectified 230VAC) to a divider of 2 200V capacitors, and due to a shorted component the entire 320V goes to one of them
Overvoltage in a doubler is not possible
You have there some other dead components - possibly the transistors or film capacitors
Besides, they are possibly a result of EOL of the tube - Have you checked the tube ? (say with a T5HO 80W ballast)
I've checked the tube with a continuity tester and both cathodes are intact. I've also checked the vacuume and it seems to glow when high voltage is applied. The ends of the tube also appear white. I can also visually confirm through the clear ends of the tube that the cathodes are intact... I think the ballast failed prematurely.
I did notice that one of the mylar capacitors is shrunken as if it shorted then began overheating.
So basically I should go the route of replacing all of the semiconductor components and caps?
Do you think the choke could have been damaged by the short out or is it more robust than that? The company thag designed the board did implement a fuse luckily.
