2006 1959HW Hum

Discussion in 'Marshall Amps' started by bstoner, Jan 28, 2020.

  1. bstoner

    bstoner Member

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    I bought this 2006 1959HW online and it looks to have a ton of mods, every pot on the front panel is a push pull except the presence pot :( Unfortunately the amp makes a fairly loud hum when standby is off. Any thoughts on who may have modified this amp and what I can try to resolve the hum?

    thanks

    b
     

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  2. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member

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    Sorry brother I am no help here at all:shrug:
     
  3. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    Take out all the preamp tubes except the phase inverter.
    Power tubes in. Master volume on 10.
    Does the amp still hum?
     
  4. ampmadscientist

    ampmadscientist Well-Known Member

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    Well
    whoever modified it did a pretty neat job. It doesn't look too bad at all.
    It might just be filament hum and not a disaster.
     
  5. bstoner

    bstoner Member

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    Which is the phase inverter?
     
  6. Chris-in-LA

    Chris-in-LA Well-Known Member

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    The last tube next to the power tubes.
     
  7. bstoner

    bstoner Member

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    No Hum with the first 2 preamps tubes removed but guitar plugged in also makes no sound
     
  8. Chris-in-LA

    Chris-in-LA Well-Known Member

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    It won’t work without all the tubes. It’s possible that the first two tubes are causing the hum. Do you have any fresh 12ax7 tubes to swap in?
     
  9. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    Yes I understand we are doing a hum test.

    Now remove only the first preamp tube V1.
    This is the tube closest to the input jack.
    Put all the other tubes back in and test for hum again.
    Master on 10.

    At this point I think you will hear some of the hum come back which means it's filament hum.
     
  10. bstoner

    bstoner Member

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    Hum is back with only the first preamp tube removed.
     
  11. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    OK
    First preamp tube is still removed.
    Master volume on 10.
    now you need wooden chopsticks to lift up 3 wires which connect to pins 123 of the V2 preamp tube socket.
    The V2 preamp tube is the small tube in the middle of the 3 small tubes.

    Lift up the 3 wires with the wood stick.
    pins 1 2 3 away from the socket straight up 90 degrees from the chassis.

    When the wires are lifted up 90 degrees vertical , does most of the hum go away?

    [​IMG]
     
    Last edited: Jan 28, 2020
  12. Chris-in-LA

    Chris-in-LA Well-Known Member

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    What? No words of caution about high voltage? OP does not seem to have a bunch of knowledge or expertise working with tube amps.
     
  13. ampmadscientist

    ampmadscientist Well-Known Member

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    It's not actually the chassis we are avoiding, it's the filament wires.
    The filament wires are connected to pins 4/5 and 9.
    We are trying to keep the grid wires pins 2 and 7, separated 90 degrees from the filament pins 4/5 and 9. :lol:
     
  14. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    OK if you can't deal with high voltage, you can hire a tech to do this for you.

    But if you die, you will be immortalized in the Marshall Amp Forum Hall of Fame for extraordinary bravery in the face of filament hum. Have confidence you will not be forgotten.
     
    Last edited: Jan 29, 2020
    marshalltsl, scozz and herbvis like this.
  15. MickeyJ

    MickeyJ Well-Known Member

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    The second preamp tube might just be screwed.
     
  16. MickeyJ

    MickeyJ Well-Known Member

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    try swapping the second tube with the last small tube, the phase inverter, does it still hum with the first preamp tube removed
     
  17. MickeyJ

    MickeyJ Well-Known Member

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    or, try swapping the second tube for the first one that youve already pulled out, does the amp still hum with the first tube removed? if it doesn't your original tube that was in the second position is screwed.
     
  18. bstoner

    bstoner Member

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    The issue is with the 2nd tube socket, moving the green wire does make the hum less but is hard to find a place for it where it is totally quiet. Also tapping on the green wire with chop sticks is very loud through the speakers even tapping the 2nd tube itself is loud I have tried replacing the tube with a good tube but the issue is still present. Im think 1300 was way to much for this amp :(. What shall I try next? See new pictures
     

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  19. marshallmellowed

    marshallmellowed Well-Known Member

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    Some basic questions...

    1. Is the hum present with no guitar or cable plugged in?
    2. Does the hum increase or decrease when any of the front panel controls are turned up or down?
    3. If it does increase or decrease when controls are changed, which ones?
    4. Have you tried jumping the channels, and if so, does the hum change?
     
  20. bstoner

    bstoner Member

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    1. Yes
    2. Yes
    3. Turning up the bass seems to make the most difference but all seem to increase the hum
    4. no change when jumping channels
    Turning up or down channel 1 does not change the volume of the guitar. Channel 2 volume does work
     

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