Marshall 1974x suddenly very quiet

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by louderock, Oct 9, 2008.

  1. louderock

    louderock Member

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    Plugged into my 1974x reissue yesterday. It works but sounds like you have a 1/4 power switch on and is quiet. Bad power tube? Something else?

    Update: Tried different power tubes. no difference. Tried different pre-amp tubes. no difference. There is one more tube that looks like an EL84 but it's not. Is that a phase inverter tube? Would that one cause the volume drop?
     
    Last edited: Oct 9, 2008
  2. kidmandude

    kidmandude Supporting Member

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    I think "that other tube" is your Rectifier tube. Your Phase inverter is a pre amp tube farthest tube away from your input jack.. V3.. It could be a bad rectifier tube if you havent checked that one out? Did you make sure all the tubes are sitting properly? Cables are all in working order? Fuses have not blown?
     
    Last edited: Oct 9, 2008
  3. acorkos

    acorkos Member

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    try a different speaker, too.
     
  4. gtrs

    gtrs Supporting Member

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    Agreed, check your rectifier tube.
     
  5. RussB

    RussB low rent hobbyist Silver Supporting Member

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    another dying transformer in the 1974X?
     
  6. louderock

    louderock Member

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    The power transformer has already been replaced on this one. Hope it's not the mains transformer. Only other tube to check would be that rectifier tube but I didn't have another one like it in my other EL84 amps. I'll check the speaker next.
     
  7. phsyconoodler

    phsyconoodler Member

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    The rectifier is an EZ81.Try that first.Usually they just die rather than give low power.The mains transformer IS the power transformer.The output transformers also die sometimes on those amps.
    Tubes first,then panic.All the tubes,not just power and rectifiers.
     
  8. gtrs

    gtrs Supporting Member

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    Crap, I totally forgot about that issue with those amps.
    Here's to hoping it's just a tube problem.
     
  9. louderock

    louderock Member

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    I think the problem transformer is the power transformer on these amps, right? That one has already been replaced. The amp does power up and it does make sound. Just doesn't make much sound. Could that mean that the output transformer is partially bad? Only working on half capacity or something? Unfortunately I don't have one of those rectifier tubes. None of my other amps have that tube.
     
  10. gldtp99

    gldtp99 Member

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  11. louderock

    louderock Member

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    Cool. Thanks for the link. I guess it's worth a shot if you guys think this could be the issue.
     

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