Hi: While I don't know for sure why RCA reduced the HV in the 5's, I suspect it was because the previous two chassis (CTC-2B, and CTC-4) applied 25KV to the 21AX, and produced a bleep-load of X-RAYS as a result. A friend came over with a radiac meter, and we measured approx. 4 milirems/hr at white screen on my CTC-4, which is a bit high, although I don't think there is too much danger unless one sits with their nose to the safety glass for a few months.
The CTC-7, and some subsequent chassis also had HV below 25KV, but a bit higher than the 5's , most likely because of the new all-glass 21CY producing fewer X-RAY's. The later leaded-glass CRT's allowed even higher HV, some around 40 KV.
Others: Please comment!
Kevin
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stromberg6
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