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RE: Question...

Posted by Jim McShane on February 16, 2017 at 19:08:59:
"If you are concerned about steel shell and leads of K72s, use FT or FCh types."

Don't forget the FT series caps have steel shells as well.

"One must thing with all Russian teflon caps is to electrically connect outer shell with one of the leads, and insulate the shell with polyester tape."

Why? If the cap is used as a coupling cap then at one lead you'll typically find high voltage DC with the audio signal riding on top of it. On the other side you'll find the next stage tube grid (most often) with a grid stopper resistor possibly in the way.

Those two connections provide COMPLETELY different electrical scenarios to expose to the shell. So what is the rationale for doing so? It seems to me that connecting the tube grid to the cap shell is asking for trouble from stray capacitance and possibly noise pickup as well.

So I am curious to find out what are you accomplishing making one of those connections to the shell. Can you share that? Thanks.