[DaveWM]

had a little set back, fly got hot, started to lose sweep and HV, turned it off, fly very hot.

checking a few things, the line voltage is high (125vac) and I did not yet switch to the high line tap, so that will be 1st. double checked the HOtube, about 215ma, at 115vac its about 200ma, playing with different 6JS6s got it down to about 195ma @115vac.

the eff coils slug is way high (mostly out of the form) to get a dip. I am going to replace the cap and maybe the coil associated with that circuit. and will replace the boost filter caps as well (if I did not to that already).

the service manual has a not about changing the HOtube screen resistor to 18k from 13k so will do that as well.

there is a diode that is connected to the aux winding on the bottom of the fly (agc/burst/hor afc... winding) thru a cap. the neg of the diode connects to the grid of the HO tube thru a 1.5meg resistor.

My guess is this is a safety circuit that cuts off the HOtube in case of hv runaway, sort of like the RCAs that use the neg voltage from the blanker tube as a safety in the same way. Besides the diode there is a cap and a couple resistors. The grid bias of the HOtube was a bit high (too low a neg) by about 10v (was -56vdc vs -67vdc) could be the vtvm calibration I suppose but that is big enough to look into. I will have to get the scope out to be sure. The scope is the only way to see if the neg bias is correct when that backup safety circuit is used (the neg reading is a composite of the two, the rectified drive from the horz osc and the rectified drive from either the diode mentioned above or the blanker tube).