CTC 5 Low high voltage

[DaveWM]

a few things, did you replace the .01 cap that could be leaky that goes to the grid? did you replace the 2mf electrolytic cap on the video board? Agree with pentode a scope reading of the grid of the horz out would tell a lot. the -20 was with the tube in correct? and what kind of meter were you using to check it? VTVM's are the best, a DMM will prob be ok but a VOM would be too much of a load.

[DaveWM]

oh and you did do a tube swap from a KNOWN working set, all HV tubes (horz out, damper, HV rec, shunt) and the horz osc tube as well.

[N2IXK]

The high cathode current and low grid voltage sure sound like low drive.

You really want a scope at this point. An external drive source like a 1077B or VA48/62 would be a great help, as well.

Start checking resistors and caps in the horiz osc. circuitry.

[DaveWM]

good point about using an BK analyst, those are great for these kinds of problems. You can quickly clear the fly with the plate drive and then move on to the grid drive to check the horz output tube. I picked mine up for 9$ IIRC, fun to have and you can make neat shadow puppets with it too

[oldtvsandtoy]

aaa

[Penthode]

Originally Posted by oldtvsandtoy

Would the -20 v take down the high voltage that much?

It is just that if the horizontal drive is low, then the resultant bias will also be low. That is because the bias is derived from the drive amplitude: eg a proper level drive will give higher bias. And the low drive would reduce the high voltage substantially.