Set Bias on Rebel 2000000000000000000000000

[old blue]

I thought the excellent post on setting the bias on the Rebel 30 might also apply to my Rebel 20, but turns out to be totally different, even though my tube compliment is the same. Here is my Rebel 20, how do I adjust the bias for the new tubes (6v6 and el34) that I just installed?

http://md02.emerald.synacor.com/service ... =co&disp=i

 

[shimmilou]

Hi old blue,

How in the world did you manage to put EL34s in there?

I get an error when I click your link.

Have you removed the chassis and had a look inside for a bias pot and test points?

 

[thickwood]

I have misspoken often and mixing up el34 with el84 so i give him a pass and assume he has 9 pin el84 tube sockets and 6v6 octal sockets i hope.
You can find the test point for both amps on the circuit board which is loaded with stuff that seems cramped.
But look carefully those 3 test points are right there,i dont need 40 per side at all,i redplated 3 tubes at 40 and above and i cant hear any difference at 37ma per side.
My tubes can handle the plate voltage but not a hot ma bias,TS 6v6 and a RI mullard redplated my bias drifted to 48ma once oops !

Be extremely careful and prop the chassis on a book against the transformer so it will not move at all leaning slightly helps keep it steady on the book !
I hooked the speaker up and moved the cord away from tripping on it and No boom !

Good luck !

 

[thickwood]

There are 2 different red test port for you DMM meter and there far apart so you will use those for the positive one at a time set your meter to the 200mvdc range and i set mine at 38 for a longer life as i did not notice improvement over that range but lower that may keep it from smoothing out in pushing the power tube in crunch.
I certainly didnt set my TS 6v6gt to 45mvdc as the board indicated,the redplate danger is quite likely with the Tungsols pushed imop !