CTC-5 21AXP22 convergence

[old_tv_nut]

Originally Posted by Penthode

Have you checked the tubes on a transconductance checker?

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The biggest drawback of the CTC5 in my opinion is the low high voltage coupled with the relatively dim (compared to tubes a few years later) 21AXP22A.

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If I get the time, I would like to explore further the Horizontal Output/ Flyback to see if I can a bit more HV.

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I suggest that the earlier less efficient phosphors in the tube coupled with the low high voltage is an inherent problem with the CTC5. Perhaps I should express my gratitude for the dim picture on the CTC5 as it probably explains why my set survived until now.

Haven't checked the tubes on a transconductance checker. I got the replacements, and subbing them mad no improvement. One of the first IF subs knocked the alignment way off for some reason.

The Super chassis has lots of drawbacks including the low high voltage.

Since I don't know how much safety factor is in the flyback design, I will not be attempting to raise the high voltage.

The less efficient phosphors are a detriment to brightness, but the greens and cyans have a purity that cannot be obtained in any later tubes (which have the more efficient but more yellowish sulfide green). Some of this colorfulness is lost due to the lower brightness. This is a well known effect in color reproduction, dubbed the "Hunt effect" due to its description by R.W.G. Hunt. Simply put, to look equally "colorful", a dim picture must have more color saturation than a bright picture.