Today's Mystery Guest (RCA CTC-4)

[Phil Nelson]

Sure, if someone has a spare metal retaining ring, I'd be delighted to use that in place of mine. On the other hand, this was a "factory approved" sort of modification, which seems less objectionable than hot-rodding an old TV. If I just cut an arc out of the ring, it should still work to support a much lighter 21AXP22.

That cambric insulating cloth sounds interesting, but I'm not finding it on the AES website. 3M makes a varnished cambric insulating tape that's rated for 69KV but quite expensive. This 3M splicing tape is also good for 69KV and cheaper:

http://www.grainger.com/product/3M-S...omCatalog=true

If you don't remove a piece from the retaining ring, I guess the idea would be to get as much insulation as possible in the small space between the anode button and the metal ring.

You could also put insulation under the retaining ring to isolate it from the bell of the CRT. As I understand the original setup, the big ring with the convergence magnets connects to ground, but the retaining ring and yoke support are left to "float" electrically. They are insulated from the CRT by the big plastic skirt, and the long retaining stays connect to the wooden cabinet with staples anchored in thick ceramic (or plastic?) washers.

Phil Nelson

P.S. I just remembered that I have a little jug of corona dope somewhere in my boxes of stuff.