I think what anyone will tell you now is to take it out and check for shorts.
leave it off for a little while though, those drive transistors on the neckboard always shock me, even after discharging the tube 74 times. lol
Polos are known for going spontaneous kablooie for no reason. if the HOT dies, that takes the flyback out too... it's weird.
if you need any in-depth help on this, wait for someone else, cause I don't work on em to this scope. I'm a capkit/cold solder kinda guy when it comes to monitors.