Re: Working with vaccum tubes


From: George, W5YR (
Date: Mon Oct 22 2001 - 15:52:46 CDT

RE final amp tanks, remember that one can replace the series feed that puts
HVDC on the stator with parallel feed that prevents it. I cannot recall
ever building a tank circuit that didn't use parallel feed. Not only does
it remove the shock hazard that Jim addresses but it allows the voltage
rating of the capacitor to handle a much higher r-f level.

Sure seems funny to be posting this to QRP-L! <:}

72/73, George W5YR - the Yellow Rose of Texas QRP-L 1373 NETXQRP 6
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe SOC 262
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
Icom IC-756PRO #02121 Kachina #91900556 IC-765 #02437

Jim Stamper wrote:

> Speaking of 12 or 15 volts, the stator plates of the final amplifier's
> "tank" capacitor in tube rigs often was hot with whatever DC you were
> applying. The rotor was usually grounded. When you were going to be
> working inside a rig it was always a good idea to close the rotor so none of
> the blades would get bent. It was also good practice to disconnect the
> power supply. Once I forgot with 600 volts DC on the stator when I pushed
> the rotor closed. I didn't realize I was "connected" until I smelled my
> finger burning.

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