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I am working on a Peavey Classic 30 amplifier. It is completely dead, no sound. All the tubes light up. The 12ax7 tubes don't seem to glow as bright as the L84 power tubes.

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Hi directmusic

You can get a circuit diagram from here.

The 12ax7's will not glow as bright as the EL34's . Is just the nature of the tubes. The latter being higher powered and the 12ax7 low power. The EL84's as output tubes will always glow brighter, and often even with a dull blue glow about the plates from the higher voltages made available to them. If the plates them selves are glowing red(inside the EL34's). then you have a bias problem. Be careful running the amp in this condition. Do some static checks with the amp off looking for failed components about the bias and screen control stages. .

Start by checking all the DC voltages first. The circuit diagram i supplied the link for has voltages marked for you to check. A common problem with this amp is the 390 ohm 5 watt resistor going open. A faulty output tube(s) may also have caused this. I would replace the output tubes anyways for a good repair.

I am more than happy to answer any other questions you may have about it, just give me a hoy :) Thanks for using FixYa, If you consider the advice I have given you as sound, a FixYa rating is a great reward for my efforts to help you. Cheers.

regards
robotek





Posted on May 29, 2008

  • Graeme Ross
    Graeme Ross Jun 05, 2008

    Hi, just a quick followup to see how you got on with your
    problem. If you still havent got it sorted, let me know, I am happy to
    do some more research and offer some more information and solutions. If its fixed...
    excellent!! A FixYa rating from you will close this unrated solution
    for me. Thanks for using FixYa. I am happy to answer any other
    questions you may have.



    regards

    robotek


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