bypassing question

[N3DRB The Derb]

yall know about my HK 257b exploits.

teh tube has parallel socket connections for the screen and the suppressor grid. so, 2 socket pins for each tube element. thats because each grid has 2 internal supports. hence, 2 screen pins and 2 suppressor pins. I'm not going to run any suppressor voltage, just going to ground them both with silver strap.

what would be the best engineering practice : bypass one screen lead or bypass both leads, and if you bypass both pins, would you increase or decrease the value? and the voltage rating for the caps needs to be 4X the nominal voltage? These tubes want high screen voltage, 500~600 volts for a plate voltage of 2 KV.

I'm not sure other tubes have this dual support structure brought out to the base like these do.

[VE3GZB]

If it were me, I'd bypass both leads and use flat strips for conductors instead of round wires. Using just one cap, you're relying on that cap's ESR. Placing another cap for bypassing puts the two ESR's in parallel.

[N3DRB The Derb]

yah, I have some solid sterling silver strap for this. often times the sterling strap you can get from jewelry suppliers is cheaper in thin gauges than copper is for radio use.

[KM1H]

At HF its not going to matter much what you do. Tie the pins together with #14 and use a pair of bypasses totaling .01 for CW/SSB or .004 for AM as in that Eimac blurb I posted. Your tubes are the same as the 4E27 and is Eimacs answer to the 813.

If the .004 is too little for full bypassing stability install 100 Ohm 2W carbons in each lead to the Esg right at the socket. Use 47 -100 Ohm in the grid leads.

Carl
KM1H

[N3DRB The Derb]

little sections of strap are a better mechanical fit for the screw terminals on old buzzard HV micas. wires fine for the socket pins but
wide and flat works better for those molded mud mica jobs.

[KM1H]

I stay far away from those old mica resistors .. Its pretty hard to beat disc ceramics for low inductance bypassing.

Carl
KM1H

[N3DRB The Derb]

well, I've never had one blow up on me, but I've heard lotsa stories. I find these days I gotta use what I have. I got molded mud micas in the correct values - I can build or I can wait until some show up on ebay or the next fester.

the last fest of the year is next sunday, so I'll be stockin up on enough caps and resistors to get me all the way to late spring.

I might actually have some HV disks - I have about 400 parts drawers.