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JTM 30 Tube Questions

  • 03-02-2010 1:51am
    #1
    ham_n_mustard
    Registered Users, Registered Users 2 Posts: 641 ✭✭✭


    Howya all,
    i have a JTM 30 1x12 combo that has been unused for roughly ten years. When i power her up, she's grand for a few minutes. Then (i reckon its when the valves warm up) she starts to sputter and lose power drastically. I'm probably answering my own question here, but would she need new tubes? If so, is it normally the power tubes or preamp tubes that would need to be done, or both to be safe?

    Cheers


Comments

  • #2
    FarmerGreen
    Registered Users, Registered Users 2 Posts: 1,134 ✭✭✭FarmerGreen


    Its usually electrolytic capacitors that go bad if you leave an amp unused for a long period of time.


  • #3
    punchdrunk
    Registered Users, Registered Users 2 Posts: 3,355 ✭✭✭punchdrunk


    these amps always had a terrible rep for reliability
    something to do with the ventilation and the internal layout of the components

    hopefully the power transformer isn't knackered :(

    i'd be getting in touch with an amp tech pronto
    replace the cheap plastic valve sockets
    re-valve the whole thing
    add Vox style ventilation grills to the top
    re-bias the amp as stoc kthey are biased way too hot!

    in truth Marshall should have recalled these amps back in the day but didn't
    hope you can sort it out as I heard the actual tone is great

    best of luck!


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