What is attached to the roller in this pic of a Homebrew on ebay?

[Naysayer]

Looks well designed but I do not recognize the big copper colored part attached between the roller and ground.
What sparked my curiosity is the Roller itself. My project makes far less than the 8877 but my roller gets very unruly at times. Roller looks the same but arcs to ground at various places sometimes. To date, I've applied insulation to prevent, but it's like whack-a-mole. I realize it's from the unused turns but there's no way to safely drain it.

 

[brandon7861]

At first glance, it looks like a tubular capacitor, but looking closer, it appears to be connected at both ends of the outer material, so I doubt that's it.

It also looks textured like it's wrapped with enameled wire. Could it be a wire wound resistor?

If I had to guess, I'd think it was something to suppress voltages on the tail end of the coil due to the autotransformer effect. I'm thinking it has enough inductance to not load down the other half of the inductor, but enough resistance to lower the voltage to a point it doesn't arc.

 

[Naysayer]

Thanks Brandon, It sounds good to the extent there may be a method to tame an unruly roller at HF.

 

[nomadradio]

Safety choke. Place in parallel with the Load control. Serves to keep the amplifier's output at zero Volts DC. Any DC leakage from the plate-blocking doorknob caps goes straight to ground through it. A shorted blocking cap should trip the high-voltage breaker/fuse. Prevents thousands of Volts from appearing on the antenna.

73

 

[Naysayer]

Oh yeah, but it's so big and nowhere near the SO-239 where I'd expect a choke. Yet it makes sense. l was hoping for some magic find. Desperation when I'm looking for ideas from ebay pics, the rogues gallery. Thanks Nomad.

 

[nomadradio]

One end of it is bolted to a grounded bracket.

Ideas? Last 50 years' ARRL handbook. Later editions of the "Radio Handbook". Latest one I have is 23rd edition. They were edited by Bill Orr, an original tube guru. Worked for Eimac, if memory serves. I found a copy of the ninth edition from 1945. Published at the time by "Editors and Engineers". Everything is push-pull triodes. With push-pull neutralizing circuits. Don't think any grounded grids showed up at all. Wartime development of tetrode/pentode power tubes hadn't quite trickled down to civilians just yet. Sideband was still off in the future. And Bill Orr's name was nowhere to be seen.

PA0FRI had a bunch of cool ideas for russki tubes. They're not so plentiful and cheap now as they were 20 or more years ago. He's an SK now, but his site is still up. https://www.pa0fri.com/
His QRO section is full of potential mischief.

73