Probably just be overly cautious, but . . .

[danny]

Hi this is an interesting fault I myself would want to get to the bottom of it. do you have an eht meter to check how much eht is actually being produced running tubes with low heater volts can damage them so might be worth a new 1b3 as the fault would indicate low eht or maybe the crt is drawing to much current. another thing you could try is to supply the set with eht from another working tv to prove the crt isn't faulty.Danny