Quote:
Originally Posted by Electronic M
If you're working with a 21" Zenith roundy change all the Sprague Bumble Bees, the white ceramic shell paper caps (I think they might be Elmenco brand), the black plastic electrolytics, and arguably the the can lytics. Adjust the horizontal efficiency coil for minimum horizontal output cathode current.
One performance mod I like is to replace the tube focus rectifier with a modern 5KV PIV 200nS recovery part from Mouser...The focus adjustment peak looks sharper, and focus is more consistently good with it.
There was talk of the 15GP22 potentially being replaceable with a 14" large neck rectangular tube found in the first Japanese rectangular color sets. The deflection angle was close enough to probably work, custom mounting would be necessary, dynamic convergence would be extremely hard to achieve if possible, but the biggest thing stopping this is that those Japanese sets are collectible and significantly rarer than CT-100s.
The RCA 21CT55 was basically a CT-100 with the sweep and convergence circuits factory redesigned to drive a 21" color CRT. I've got working examples of both. The 21CT55 uses R-Y/Q demodulation instead of I/Q demodulation...The only difference is one demodulator transformer and 1 resistor. I acquired a spare CT-100 I/Q transformer and plan to convert my 21CT55 eventually.
I've seen someone who blew up the flyback in their 21CT55 and replaced it with one from a CTC-20 roundy color...If someone was REALLY motivated it might be possible to take a CT-100 look at the 21CT55 sweep/convergence differences and try to implement them with say a CTC-17 rectangular set's sweep circuits and use that to drive a 15NP22...It would be a Frankenset at that point.
I've also seen 13-15" rectangular service test jig CRTs with yoke impedance matching boxes(to make them compatible with everything from 60s roundys to 90s BPC). It could be possible to impedance match a 15" inline gun rectangular CRTs yoke to the stock sweep of a CT-100. If done correctly you wouldn't need dynamic convergence or chassis mods, just new CRT mounting. Seeing as other members have run 60s roundy CRTs off 15GP22 sets for test jig reasons this mod should be possible to implement.
If my 15G ever craps out I may try some of these ideas.
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I Remember seeing one of those Japanese rectangular oddities on the bench at the Ft Jackson Army post electronix craft shop I frequented in the 1970s, I think Hitachi or Toshiba for Sears.
I was going to ask about that set in a posting.