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I just acquired a pair but don't know how to bias them. Any help is appreciated.
Follow Ups:
Ok
You pull the bottom off and and underneath you will see the bias pot mounted on a little bracket off to the right.You basically put your meter on pin 5 of of the EL34 tube and adjust that pit until you get minus 33vdc.
The other pot is an AC balance and unless you have a signal generator and a scope,all you can do is set that pot at the center of rotation.I have a pair of 255s and you can also run 6L6s in these amps and the output trafos are 6.6k which is ideal for a 6L6.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 10/02/16
Mike do you prefer the 6L6 to the EL34 in tihis amp? Can the power transformer take the extra requirements of KT66?
Yes those can take a KT66 because the KT66s draw less filament current than an EL34.When you put KT66s in or 6L6GCs,you need to set the negative bias on pin 5 at about minus 40vdc to 42vdc.If I were you I would change the coupling caps in these amps and put a 1N4007 diode across the selenium if these things weren't done yet.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 10/02/16
Looks like there may be room for 2 x PIO and FT-3 for the first cap. What did you use?
I used K40y pio caps but you can use Teflons.The caps in there are not too bad actually. I like the rebuild they did. What you can do is put a 35uf film cap off the 5V4 and that would clean them up even more.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Are the GZ34 and 5V4 interchangeable regardless of whether they are 255 (6L6) or 255a (EL34)?
Gz32 is a sub for the 5v4
real radios glow in the dark...
Yes I am aware of that. The 255a calls for a GZ34.
I'm sorry ,I had a brain fart as I very well know that the 255 uses a gz34 although the 260's and the 275 each use a pair of 5v4.
real radios glow in the dark...
Edits: 10/04/16
Great thanks Mike.
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