JCM 800 Issue (2204)

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by ecbluesman54, Sep 15, 2008.

  1. ecbluesman54

    ecbluesman54 Member

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    My JCM 800 has performed flawlessly for a long time. Yesterday I went to play it, and I am getting no sound st sll. All cables (including guitar), power tubes, and preamp tubes are good, and brightly lit. I am not getting any noise through the speakers (no hiss). I checked the cab with a different head, and it's not the cab. I also tried plugging into the low input. I checked the fuse and it is fine as well. Any advice on where to start looking? It is a 50W JCM 800 Canadian version from 1984. Let me know if there are any questions that need to be answered that I have not described.

    Thanks for the help!!!
     
  2. skipm45

    skipm45 Member

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    A few things:
    Does the standby switch "feel" odd at all when operated?

    If you replace the tubes one at a time does it make a difference?

    Without measuring any voltages it's a shot in the dark.

    If you're comfortable with this (BE CAREFUL) measure the other side of the standby switch and see if the HV comes "on" when the switch is closed.


    HTH

    Skip
    www.skipzcircuits.com
     
  3. FrankieSixxxgun

    FrankieSixxxgun Member

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    Just because the heaters are lit does not mean the tubes are okay. Heaters will still light up even on a dead tube, and 99% of tube amp problems are tubes.
     
  4. ecbluesman54

    ecbluesman54 Member

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    Thank you for the recomendations so far. As far as the stanby switch, the Canadian models had metal switches, so it feels the same.
    I will check out the tubes.
     
  5. phsyconoodler

    phsyconoodler Member

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    Try a new 12AX7 in V1.That tube is the most common failure on a 2204.
    There are also lots of fuses inside the chassis on the Canadian models.Rather overkill IMHO,but they are there.
     
  6. joepopp

    joepopp Member

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    Try working the voltage and impedance switches back and fourth, This stumped me one time. Just a shot...
     
  7. drgonzoguitar

    drgonzoguitar Member

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    with the amp unplugged!
     
  8. ecbluesman54

    ecbluesman54 Member

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    Thanks to all of you that gave some advice, I really appreciate it. Psychonoodler, it ended up being two of the fuses inside that were blown, I replaced them, and turned it on, and everything was good again.
    Thanks to everybody again, you've saved me some $$ and time!
     
  9. joepopp

    joepopp Member

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    Good lord YES! Sorry to leave out that important tid bit.
     
  10. VikingAmps

    VikingAmps Member

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    Hey watcha doin over here? Dis aint da Palace!
     
  11. FrankieSixxxgun

    FrankieSixxxgun Member

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    Da palace is slow sometimes and I need me gearhead fix more and more these days! They got Betty Ford for Marshall addicts? :D
     
  12. VikingAmps

    VikingAmps Member

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    The twelve step program would never work with a Marshall, they can be heard much farther away.
     
  13. phsyconoodler

    phsyconoodler Member

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    The Canadian version has fuses that are not required really.They blow at odd times just for no particular reason.This does not mean you should replace the fuse and forget it ever happened though.
    You should check the amp over and likely it's a signal that you are getting close to needing new tubes and a bias job.
    People can tend to run those amps pretty hard because they sound so good cranked.
     

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