Lighting experiment - WWOC on CTC-5

[old_tv_nut]

Originally Posted by Penthode

The lighting is excellent! The key appears to be the rear lighting and diffusion of the front. The shot has a good contrast ratio.

Have you done any absolute measurement of peak white off the CRT before blooming? Would be curious to see if I can borrow a light meter to do some quantitative brightness tests. Certainly it would be interesting to compare 21AXP22 brightnesses.


The 21AXP22A in my CTC5 appears to be tracking well but is noticably dimmer than the 21FP22 in the RCA CTC 11 and even the well used CRT in the Zenith 24NC31Z. I assume this to be normal.

Is your CTC-5 the Super (cost cut) or DeLuxe chassis? This is a Super, which has pitiful brightness due to low high voltage, and I suspect lower video drive as well. I have been having thoughts of checking the high voltage and retubing the H output / high voltage section, which I haven't done since I got it running. Then it might make some sense to measure brightness. I can tell you that the 21AXP22 was visually dimmer than the 21FBP22 when I swapped it in.

According to a paper by Austen E. Hardy of RCA, the white-light efficiency of CRTs increased as follows:

Tube Type, Lumens per watt:

15GP22 0.6
21AXP22 1.0
21CYP22 1.4
21FBP22 (all sulfide) 2.6
21FBP22A (early vanadate rare-earth red) 2.9