Feed thru capacitors

[Naysayer]

Since my big bang event a few months ago (homebrew 4cx300a amp), I’m planning on taking advantage of the required disassembly / troubleshooting to replace the RF input (parallel inductance a’la Pride) rotary switch circuit with a 4 band relay board fashioned from an LPF kit. It should fit inside the blower box and reduce the amount of wire/capacitance.

The switch effort did help me find the needed inductance values for each band so I can settle on only four (10, 15 20, 40). Looking at handheld VNA’s now, even with the time spent learning how to use it would have saved me some time. What’s that saying about taking the time to smell the roses? I also replaced the air variable Load cap with a more appropriate unit.

Under ‘Better late than never’ I learned that the old feed-thru connectors (Eldico deck) I removed long ago were actually feed-thru capacitors. The ceramic was crumbling so I replaced them with ordinary feed-thru’s. Ordered new ones to re-install. Any suggestions on when to use or when not to? I assume they would be appropriate for any line except an RF line. AC tube Heaters?

 

[nomadradio]

Screen and grid-bias circuits, or meter wires from a meter that's above the deck and exposed to radiated RF from nearby plate-circuit components. Mostly I'm used to seeing them feeding into and out of an enclosed shield around the tube socket's underside. An amplifier using a swamped grid circuit probably doesn't need that level of sophistication. A swamping resistance on the control grid enables all manner of sloppy design with few penalties. But a neutralized amplifier probably should have all the filtering you can afford.

73

 

[Naysayer]

Thank you for Reply. "...all manner of sloppy design...''' sounds workable without but I already ordered a 1/2 dozen so I'll use them on the rebuild where I can.

 

[nomadradio]

Extremism in the defense of decoupling is no vice.

With apologies to K7UGA.

73

 

[Naysayer]

OK I'm feeling good at that. Last night I removed tube sockets from blower box to rewire before I start troubleshooting my bang event. Hoping it's not the Tetrode Boards. This time I'm going for minimalist: As few wires as possible to reduce inductance & capacitance.