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Tube experts - Rattling sound coming from one of my tubes...help!

Discussion in 'Amps and Cabs [BG]' started by Ty McNeely, Oct 21, 2001.

  1. Ty McNeely

    Ty McNeely

    Mar 27, 2000
    There is a rattling sound coming from one of the tubes (Groove Tube 6550C) on my 300T. It was there when I bought it, and there's nothing wrong with it, but I'm just curious. It only makes a noise when I play an E (any E, doesn't matter which).

    It's not really a major nuisance or anything, but I just want to make sure the dern thing isn't gonna crap out on me anytime soon or me cause any major damage to it.

  2. Jerry J

    Jerry J Supporting Member

    Mar 27, 2000
    P-town, OR
    This is what is called a microphonic tube. It is physically loose and rattling. It may be fine and last as long as the other tubes. Or then again it may give out. You may want to look at and see if you can see if the base is loose from the pins. BE SURE AND POWER DOWN THE AMP, UNPLUG IT AND WAIT UNTIL THEY COOL DOWN. Also try not to get greasy fingerprints on the glass if you can help it. If the pins and base are loose use a small bit of super glue to help there. Tubes are reletively cheap and I would replace it unless it's an NOS American which I'd use until it's gone bad.

    Be sure if you do replace the tube that it is matched to the other tubes. I think that Groove Tube has a matching system that matches the transconductance.
  3. Ty McNeely

    Ty McNeely

    Mar 27, 2000
    Thank you Jerry! I'm not exactly sure how to get into the amp, however. I DID know to make sure the tubes were cool before I messed with them, but other than that my knowledge of amps in general is fairly limited. I can't actually SEE anything moving or rattling around, but like I said nothing is wrong with it so far.

    I just bought the 300T about 4 months ago or so, so I don't think that it's any special tube.

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