TNT Power Supply Upgrade

Ignore the dates on this and subsequent posts. A number of things have been happening over the past few months with the TNT and with life. I haven’t taken the time to blog about developments, so I’m now catching up.

One day it occurred to me I should be able to use my Heathkit PS-23 power supply with the TNT. I mounted a 1920s 3 ohm rheostat in the bottom of the PS-23 to adjust filament voltage, and put the whole supply on a variac. A bit of careful twiddling of the rheostat and variac produced 7.5VAC for the UX-210 filament and 550VDC for the plate. Perfect!

This arrangement has been found to work well. With my 50K grid leak I am able to load the rig to somewhere between 35 and 45 milliamperes plate current on the various bands, for 19 to 25 watts input. Output is between 5 and 8 watts depending on the band and the trade off between power output and best note.

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