Ye Hector:
I think you have it sorted out. I came to this same conclusion. My house power is rarely below 120VAC. AC heaters are quite straight forward. I am just a little unsure how much tolerance the heaters have around the target voltage. I am expecting it to be 10% or so. Therefore 20V should be fine.
Thanks to all for the comments and help
I think you have it sorted out. I came to this same conclusion. My house power is rarely below 120VAC. AC heaters are quite straight forward. I am just a little unsure how much tolerance the heaters have around the target voltage. I am expecting it to be 10% or so. Therefore 20V should be fine.
Thanks to all for the comments and help
I have seen both +/-10% and +/-5% quoted, but as you may notice it's hard to find this number when you look for it. Generally, I have only seen the 5% spec associated with military or other high reliability tubes. A quick run through of my data sheets finds no spec for any of the series string tubes like the 21LU8. I do see a 10% spec for a high reliability computer tube, the 5963, and the twin triode regulator 5998. A 20 volt transformer will likely give you a bit over 20 volts anyway, so that's probably the best choice.
Hello George:
Thanks for the thoughts and words of encouragement. The adventure begins again.
The first up will be a 21LU8 PP based on the design my member Jane and published on a German web site. Tony spoke highly of it when he built his version of it.
Here we go. I will start a new thread regarding that build.
Thanks again.
Thanks for the thoughts and words of encouragement. The adventure begins again.
The first up will be a 21LU8 PP based on the design my member Jane and published on a German web site. Tony spoke highly of it when he built his version of it.
Here we go. I will start a new thread regarding that build.
Thanks again.
I never tried them in a push pull amp but I did build a little SE SPUD board with the 6LR8 and tested it with the 21LR8. These are the 9 pin versions of the 6/21LU8. I found a 21LR8 with an obvious crack in the glass so I attempted to make the crack worse. The tube won that challenge. I had some other ugly looking tubes so I tested them to 500 volts!
Attachments
Thanks John:
A useful article about Over voltage. The risks of vintage transformers on modern mains power.
George:
Sometimes I think you operate in a different universe than the rest of us "normal" folks. I love reading your anecdotes and adventures into the world of tube torture.
Take care
A useful article about Over voltage. The risks of vintage transformers on modern mains power.
George:
Sometimes I think you operate in a different universe than the rest of us "normal" folks. I love reading your anecdotes and adventures into the world of tube torture.
Take care