RCA CTC4B "Gainsborough" picked up in San Francisco

[miniman82]

We're talking 24kv+, I don't think paper is gonna cut it. You need something thick with high dielectric strength like phenolic, nylon, plastic, ect. FWIW, once you fix the obviously high horizontal current situation I doubt you'll have the issue crop up again. It happened because the insulating wax melted away, allowing the HV to find the path of least resistance.

[old_coot88]

I was gonna say the same thing re. fishpaper. It's useful in lower-voltage applications, but I sure wouldn't use it here.

[Phil Nelson]

I used some of this 90KV-rated cambric tape when transplanting a glass CRT into my CTC-4. I still have much of the 20-yard roll left. Send me a PM and I'll mail you some to insulate that spot where the arcing occurred.



I would reserve judgment on the flyback until you can remove the wax and carefully inspect the winding.

Apart from this little incident, if you're getting a good picture from RF input, that sounds like great progress.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[ohohyodafarted]

Chris,

Just goes to show you learn something new every day. I had always wondered about the 3 different CTC4 chassis. I did some investigating and in one of my RCA service bulletins I found a chart defining the 3 different chassis. The 21ct660u and 661u in the two low end Seville and Haviland models, used the early production CTC4 chassis. The 21ct662u Director, used the CTC4A. The 21ct663u Cheltenham and 21ct664u Gainsborough used the CTC4B.

There are a fair number of circuit differences, mostly in the color circuits, between the CTC4 and CTC4a. I don't have a CTC4B RCA schematic so I am not sure where the circuit differences lie in the CTC4B version.

Unfortunately I got my Cheltenham without a chassis. It was just a gutted cabinet. I have a CTC4 and CTC4a chassis to work with but I do not have a "B" version. And what is worse, the CTC4A I have has been canabilized so I am not certain which direction I will proceed. I am leaning toward rebuilding the "A" chassis but that will entail finding a pile of spare parts that are missing. Clearly the CTC4 early version is not correct for a Cheltenham.