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I found out about using Varistors to stop voltage spikes from Rob Robinette's wonderful Website. He suggests TDK 625v Varistors for the DC plate / Output transformer protection, and that's what I've used. https://www.mouser.com/ProductDetail...jRPStIMZVHlPc=
But I decided against using that high a voltage Varistor for the AC line protection, and went with a lower 470v unit recommended by Digikey. https://www.digikey.com/product-deta...1434-ND/593833
Here's my question : I realize AC peaks at above 125vac and you need something more than that voltage, or risk burning out the Varistor prematurely, but what voltage is appropriate for AC to protect your transformer ? How about DC at the output tube plates, is 625v to far away from the approximate 350vdc volt DC on most of my amps, or is it just about right ?
I would like to understand how to properly size Varistors, and not have too low or too high a voltage rating, or for that matter too few or many Joules ratings.
Also, how likely is it for a transformer to be damaged by a very fast voltage spike, up to the point of a 470v varistor kicking in ?
Thanks for any help !!!
But I decided against using that high a voltage Varistor for the AC line protection, and went with a lower 470v unit recommended by Digikey. https://www.digikey.com/product-deta...1434-ND/593833
Here's my question : I realize AC peaks at above 125vac and you need something more than that voltage, or risk burning out the Varistor prematurely, but what voltage is appropriate for AC to protect your transformer ? How about DC at the output tube plates, is 625v to far away from the approximate 350vdc volt DC on most of my amps, or is it just about right ?
I would like to understand how to properly size Varistors, and not have too low or too high a voltage rating, or for that matter too few or many Joules ratings.
Also, how likely is it for a transformer to be damaged by a very fast voltage spike, up to the point of a 470v varistor kicking in ?
Thanks for any help !!!