This is a common question about the circuit.
When the 833A tube is not conducting, it doesn't actually show the 4000 volts
to the filament or triac. The triac switches while the 833A tube is not conducting.
The 833A is basically open-circuit at this time. It's as if it's not there.
By the way an SCR is more robust than a triac and can be used instead.
I used a triac in my original staccato because that's what I had on hand.
In later work I used SCR's. This is more important for more powerful VTTC's.
Actually I used just a simple transistor in an even earlier staccato circuit.
John
-----Original Message-----
From: Steve White <steve.white1@xxxxxxxxx>
To: Tesla Coil List <tesla@xxxxxxxxxx>
Sent: Thu, Jan 25, 2018 11:42 am
Subject: [TCML] VTTC schematic triac question
I don't have much expertise with vacuum tubes. I am more of a transistor person. My question concerns the 833A VTTC schematic of Steve Ward. I have recently completed a VTTC based on this design and it works well. My question involves the triac used for staccato operation. The schematic specifies a triac with only a 480 volt rating. From the schematic, it appears to me that this triac has to hold off about 4000 volts when switched off. Am I correct or am I missing something? Why is a 480 volt triac adequate?
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