CTC-17 Screen control issue

[bgadow]

Originally Posted by old_coot88

Yes. You guys are probably already familiar with it, but there is a "last resort" trick in dealing with high cathode current on the HO tube. That's to get ahold of a few assorted 6KV disc ceramics of 68, 82, 100, and 120 pf or thereabouts, and, starting with the lowest value, clip it across the damper tube, direct from cathode to plate. This will drop the HO's K current a little bit. Then try the next higher value, which will drop the current a little more. A drop of 10-15 ma. should be possible. And the sweep width will increase. BUT as as with any trade-off there is no free lunch. The HV will drop concomitantly. Usually there is an acceptable "happy medium" that can be struck.

I've used this 'last resort' method to get a little more sweep in cases of insufficient width (it works on BW too. 4KV rating is sufficient in BW sets).

Also there were some flyback-eating 25" Admirals using the 6KD6 HO tube, where the K current would often exceed 400 ma. I also dropped the G2 voltage on the tube a bit, juggling it with the damper cap value, to get an acceptable trade-off between Kcurrent, HV and width.

I, for one, had never heard this trick. I need to print it out because I have the feeling it will come in handy some day. In particular, I have an Admiral with HV problems.