New tube bias problem in a 210-65

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Author Message   Greg Williams (gwmn) Username: gwmn Registered: 08-2013 Posted on Friday, August 16, 2013 - 08:41 pm:    Has anyone had a problem with new JJ 6CA7's and biasing. I just replaced all the caps in this amp and bought some new JJ's. At first I thought it was my cap job, but I switched the tubes, keeping them in the same probes, and the one tube climbs to the moon (I shut it off at 40) after warm up in either socket. The other tube is fine (stays at 21) in either socket. Bad tube? Thanks for any feedback   Greg Williams (gwmn) Username: gwmn Registered: 08-2013 Posted on Friday, August 16, 2013 - 09:20 pm:    Also, would it cause any grief to use one of my old Sylvania 6CA7,s along side the good JJ? I,m itchin' to play this thing.   Mike Kaus (mm210) Username: mm210 Registered: 05-2006 Posted on Saturday, August 17, 2013 - 06:06 am:    Sounds like a bad tube. You COULD use the old 6ca7 in conjunction with the JJ if they are close enough in current draw but I haven't seen too many JJ's that pull the same as an old tube. Good tubes but they DO require different amounts of bias voltage.