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Early EL84 Tesla Roznov Rounds
Posted: Mon 02/20/06 3:12 pm
by ajkimba
Just wondering if any of you guys have found these tubes to require a higher then usual biasing resistor?
Most all of my other NOS and used Old Stock EL 84's are running great on 125 to 140ohm but these great sounding Tesla Roznov Rounds I got are slightly red plating with a 140 ohm...? Just wondering if anyone else noticed this with these tubes...?
Posted: Sat 10/21/06 9:42 pm
by Lefty
I had a pair of Tesla EL84 rounds red plate on me also. This was in my JA TMB using the stock 130 ohm cathode resistor. Think I'll change it to a 150 just to be safe.
Im also running a 120ohm bias resistor on my lite IIb
Posted: Sun 10/22/06 3:11 pm
by jtmjtm45
should I go to a 150ohm insted of the 120 ohm.I couldnt find the 150 when I built it???
Re: Im also running a 120ohm bias resistor on my lite IIb
Posted: Sun 10/22/06 6:30 pm
by ajkimba
jtmjtm45 wrote:should I go to a 150ohm insted of the 120 ohm.I couldnt find the 150 when I built it???
I would, 150 ohm is a good medium value to safeguard tubes and not have a cold bias. A lot of people here use 150 and even higher.
Posted: Mon 10/30/06 6:06 pm
by Wicksy
I used 180 ohms when installing some NOS Polams. They were red plating slightly at 150ohms.
Posted: Mon 10/30/06 6:14 pm
by brownnote
I've had very bad luck with the NOS Tesla el84's, I bought up a bunch of em a while back and they all performed very poorly biased with 150 ohms. I thought they woulk be great becuase the 12AX7's sound so good, but not the batch I got.
Posted: Tue 10/31/06 12:26 pm
by markh
I always put in at 180 to start and then parallel a low watt larger value to bring it down as necessary, e.g, a 910 in parallel will bring 180 down to 150.
--mark h