Big differences 6L6 Svetlana Winged "C"

[sergio]

Hi , Today I replaced the svetlana 6L6 on my ODS Clone 100w(run about 37mA), I restored with a new quartet of Svetlana 6L6 winged "C".
After turn on the standby (with same bias setting)I seen bias current rise as far 65mA , almost twice of old tubes.
Have anyone ever found similar differences with same brand?

Sergio

[vibratoking]

I've seen that many times. You'd think the tolerances would be tighter, but they are not. That's why we have bias adjustment.

BTW, 37mA is a little high for an ODS. I prefer to run mine down around 32-33mA. There is nothing written in stone here, so adjust to taste and calculate the dissipation so that you don't burn them up to quickly.

[Bob-I]

Sergio, did you wait for the amp to warm up fully? I've seen some big changes in bias current after warm up.

[sergio]

Bob ,the amplifier has one year already, I couldn't let it warm up because it seemed too 65mA at rest, and I turned it off immediately.

37mA with 440V plate I'm not seems hot biasing!!! not so extreme!

[Harald.Nowak]

Hi , Today I replaced the svetlana 6L6 on my ODS Clone 100w(run about 37mA), I restored with a new quartet of Svetlana 6L6 winged "C".
After turn on the standby (with same bias setting)I seen bias current rise as far 65mA , almost twice of old tubes.
Have anyone ever found similar differences with same brand?

Sergio

My 2 cents: Svetlana 6L6 (made in St Petersburg if I'm not mistaken) are known for having large variance in tube parameters and also quality and longevity, so I wouldn't be astonished about that - bias them down and all is fine.

[Bob-I]

Bob ,the amplifier has one year already, I couldn't let it warm up because it seemed too 65mA at rest, and I turned it off immediately.

37mA with 440V plate I'm not seems hot biasing!!! not so extreme!

I've had correctly biased amps go as high as 70ma when first powered on. I always let my amp warm up for 10 minutes or so before adjusting the bias.