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Marshall Jcm 2000 Dsl 100 Crackling Static Issue

Discussion in 'The Workbench' started by assclown, Oct 10, 2018.

  1. assclown

    assclown New Member

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    Hello all,
    I'm sorry if this is a duplicate post from elsewhere but I was wondering if anyone else had some tips for me on troubleshooting my amp issue.

    I have a marshall jcm 2000 dsl 100 with 1960A cab and just recently it has started crackling and the sound is not as loud as usual.

    So far the things I have done are:

    Replaced all pre amp tubes
    Chopsticked power amp tubes
    Applied contact cleaner to all tube sockets and also all jack connections and left overnight plugged in
    Tried multiple different leads
    Tried multiple different guitars

    When I plug the guitar into to return on the effects loop, the crackling and static completely disappear.
    Is there anything else I am missing here? I haven't replaced the power tubes as they don't appear to have anything wrong with them and to be honest, I've never heard what a bad one sounds like.

    I have made a couple of videos of this issue if you don't mind having a look.
    Thanks in advance.



     
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  2. ampmadscientist

    ampmadscientist Well-Known Member

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    "When I plug the guitar into to return on the effects loop, the crackling and static completely disappear."

    THE RETURN JACK HAS BAD SWITCH CONTACTS.
    Replace the return jack, that will fix the problem.

    A. You "can" clean the contacts but that is only temporary. Replacing the return jack is the only permanent solution.

    B. Plug a guitar cable between send and return - that will bypass the bad switch contacts. You can play the amp, as long as the jack contacts are bypassed.

    C.
    Replaced all pre amp tubes
    Chopsticked power amp tubes
    Applied contact cleaner to all tube sockets and also all jack connections and left overnight plugged in
    Tried multiple different leads
    Tried multiple different guitars

    You did all that for nothing. Your old preamp tubes are still good.

    D. Soldering: it is better to have a pro remove and replace the bad effects jacks. Soldering can damage the circuit board. You need professional soldering equipment to do this correctly.
     
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  3. assclown

    assclown New Member

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    Thank you for your reply I really do appreciate the feedback :)
    I jumpered the send and return jacks in the effects loop as you suggested but the static is still there.
    I have taken another video of this below. Do you still recommend I replace the return jack or the send as well?



    Cheers
     
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  4. Mavrim

    Mavrim Member

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    Check all solder connections on the board. I had an intermittent low volume or static issue. Turned out that there was a solder void around one of the resistors going to the plate resistor on the phase inverter.
     
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  5. assclown

    assclown New Member

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    Am currently investigating this issue again now that I have free time. ALL input is greatly appreciated guys.

    Cheers
     
    Mitchell Pearrow likes this.
  6. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member VIP Member

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    I have nothing to ad but I do believe that you will get to the bottom of this:cheers:
     
  7. Marcell

    Marcell Active Member

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    Solderingconnections and clean pots. I woud say preampboard ... I don 't know this amp..has it a separate preamp board? Or are the inputjack and pots directly soldered on the board? I've that is the case.. inspect Thoose areas with a magnifing glas very closely.
     
  8. assclown

    assclown New Member

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    Will take all of this advice given. Will report back my findings in case anyone else has this issue. Thanks for the input guys and gals????
    I should note sorry.... I have done a freeze spray test on all of the solder points on every pcb in the amp and no change to the crackle/ static
     
    Last edited: Nov 6, 2018
  9. ampmadscientist

    ampmadscientist Well-Known Member

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    Did you freeze the resistors in the preamp one at a time?

    Did you re-solder the input jack?
     
  10. anitoli

    anitoli Well-Known Member Gold Supporting Member

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  11. assclown

    assclown New Member

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    Each resistor was done individually with no obvious change in noise. Dabbed the input and effects jacks with solder but have ordered replacement jacks for all. As I'm in Australia, postage is taking a while. Nearly 2 weeks waiting. I'll keep nutting it out and thanks again for the advice Will post if any improvements.
     
  12. ampmadscientist

    ampmadscientist Well-Known Member

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    OK
    take the V1 preamp tube out. The tube closest to the input jack.
    Is the noise still there?
     
  13. FourT6and2

    FourT6and2 Well-Known Member

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    If the noise goes away when you plug into the return jack it means the source of the noise is BEFORE the jack in the circuit. So that should help you narrow it down some.

    That said, most noise issues like this are from power tubes.
     
  14. assclown

    assclown New Member

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    Hi, jacks have arrived and I'll try and install them next week. I took the V1 preamp tube out but the noise is still there :(
     
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  15. assclown

    assclown New Member

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    Just wanted to update you all on the progress of this for future reference. After resoldering every possible point known to mankind, the noise has gone with no replacement parts required to be used. Thank you very much for all of your advice and giving me options to work through and solve it. Pretty stoked right about now.
    Cheers
     
  16. ampmadscientist

    ampmadscientist Well-Known Member

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    "I took the V1 preamp tube out but the noise is still there..."
    "I jumpered the send and return jacks in the effects loop as you suggested but the static is still there."
    "When I plug the guitar into to return on the effects loop, the crackling and static completely disappear.:

    Do this again:
    Plug guitar into the effects return.
    Turn guitar to 10.
    Turn the master volume up to 10.
    Is the noise still gone?

    Take out V2 preamp tube, turn the volume up high.
    Is the crackle still there?
     
  17. assclown

    assclown New Member

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    Hey, thanks for the advice but it has been fixed as explained above.

    Cheers
     

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