Early Sylvania Roundie on the 'Bay

[old_tv_nut]

Originally Posted by Steve McVoy

3 ma can't be right. That would be 60 watts at 20 kv. Since the voltage drop across each diode would only be 300, I don't see a problem with arcing except maybe at the ends where the diodes would have to be looped around to fit. HV insulating cambric would solve that.

Rough calculation (real current will be less, since it will be limited by max red gun current):
21AXP22 spec says absolute max average current 500 microamp per gun. I was just doing the calculation to show that the zeners could withstand more than enough current to handle a black screen. (To stay in regulation, they should still be taking some current on a max white screen, when the CRT draws less than 1.5 ma. So, the flyback has to supply something slightly above the max designed CRT current, and that value has to be less than 1.5 ma. (maybe 1 ma? maybe 1.2 ma? maybe less) Then, when the CRT anode current goes between 0 and 1 ma, the regulator goes between 1.2 and 0.2 ma.

Something like that, although I don't know what the fly is capable of and what typical beam currents are in this set.