bright orange power tubes

Discussion in 'Amps and Cabs' started by jdavyd, May 28, 2008.

  1. jdavyd

    jdavyd Member

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    has anyone ever seen power tubes light up completely orange? i don't mean in a subtle way, either, i mean as bright as light bulbs on full. if so, what was the cause? this happened to me once a few years ago, and the amp (for me it's a block letter 5150) has been sitting ever since. i've got the bug to have a tech go over it, but am curious as to what i may be in for.

    it won't kill me if i don't get it going again, but all the same it's a sweet rock amp so it's a shame to just have it sitting here doing nothing...
     
  2. sinasl1

    sinasl1 Member

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    Dat be called RED PLATING.

    TROUBLE.

    You don't wanna blow a screen resistor on a 5150 either- they are a bitch to get at. Have a tech go through it and retube it with something robust (JJ 6L6's seem pretty tough).
     
  3. jdavyd

    jdavyd Member

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    i should mention that a tech went over it a few months before it happened, replaced the power tubes and the "bias resistors." at the time i had no clue what resistors were but i took him at his word. the consensus has been "get a new amp tech." heh. no doubt.
     
  4. sickboy79

    sickboy79 Member

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    You're talking about the actual plates being a reddish/orange color, right? If so - that is indeed red plating - which is not a good thing. The tubes are running to hot. It's usually a symptom of the bias being to hot.
     
  5. Blue Strat

    Blue Strat Member

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    Or even more likely, the bias circuit has a problem.
     

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