Another RCA CT-100 discovery B8001599

[dtvmcdonald]

Originally Posted by Electronic M

The 15GP22, Its advanced phosphor deposition CBS equivalent the 15HP22, and the much rarer 19" version (19VP22?)...All used electrostatic dynamic convergence (something like 6KV DC with 3KV AC riding on it) instead of the electromagnetic dynamic convergence the 21AXP22 and all later color tubes used until inline gun tubes eliminated dynamic convergence.

There's 3 adjustment screw magnets on purity coil* that are used for static convergence the same as later tubes.

*Instead of degaussing these tubes use a field neutralizing coil on the face and a purity coil on the neck....As a working CT-100 owner it took a little bit wrapping my head around how the adjustments work (and they're still not perfect thanks to a bent shadow mask), but it wasn't hard making them pretty good. There's less to a 15G convergence procedure than most later sets...only problem is HV tends to bloom and fluctuate (especially given I don't have enough high VA voltage regulating line isolation transformers to run my CT-100 off of)and the user pots for focus and occasionally convergence DC have to be tweaked to keep things looking good.
If I had enough room to put my CT-100 and 21CT55 in the same room I could make them share the transformer that feeds the 21CT55.

Actually the convergence for the CT-100 is a real chore. The reason is that
the tilt and centering of the deflection yoke is super critical. Its more critical for convergence than for purity. The good news is that essentially perfect
convergence is possible. The only reason my set does not have perfect convergence over the whole screen is a bit of ringing in the horizantal sweep.
This makes one vertical line in the crosshatch pattern be off in the blue.
Across the rest of the screen all lines are within 1/2 linewidth of perfect,
and most really are perfect.

In preparation for work on color sets at the ETF next week I checked my own CT-100 last night. In addition to convergence, in a dark room the color rendition is truly perfect, using both my own patterns and "Digital Video Essentials". On the usual "blue bars" matching test, and the equivalents for red and green on my own test patterns, all three colors are perfect.
This was only achieved by tweeking one of the matrix resistors long ago ...
its not needed changing since.

As I have said before ... if the cameras were tweeked as well as the (Model 5) sets for the demo for the FCC, everybody must have been stupefied by the quality. The I-Q system really does the job. I consider the ideal viewing distance for the CT-100 to be three feet! I routinely watch football, golf, and baseball on mine.
the viewers of the