Yeah, we built one of those from Rich's plans almost 20 years ago. Has been incredibly handy. His suggestion to test breakdown between grid and cathode is what we use for the 3-500Z, 4-400 and such.
Oddest thing I see doing that is the occasional relaxation oscillator. A loose grid wire will literally "sing" and make accoustic noise you can hear coming from the tube. And if a CB happens to be turned on in the room, you'll hear a buzz in the speaker from the arc inside the tube. The first wireless transmitters did use an arc as the RF source, after all.
Turns out the real value from that tester comes from taking the two HV secondary wires loose in a SB-220 amplifier and checking them for breakdown or leakage to chassis ground. Always better to warn the customer his HV transformer is on the edge of a cliff before big money gets spend on new HV filter caps and such.
Got tired of discovering a bad HV transformer after a few hundred bucks got spent on an amplifier.
Before is better.
The neon-sign transformer at the heart of his setup is becoming an extinct dinosaur, year by year. High-brightness LEDs largely replace neon in custom signs nowadays. And even the diehards who use neon tubes have solid-state switchmode power lighting them now. Might want to track down an old-school neon transformer before it's too late if you contemplate copying this design.
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