JVM 205H 50amp Cuts out during performance AGAIN!

Discussion in 'The Workbench' started by Ivor Carter, Dec 3, 2019.

  1. Ivor Carter

    Ivor Carter New Member

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    This amp has let me down during a gig a number of times.
    It's been to a tech and he can't find anything wrong with it.
    It's speaker lead input related. During the gig during a song it cut out, I went back to the back of the amp wiggled the speaker lead and it came back on for a bit and off. This happened several times. The next time it happened I had another newish speaker cable and plugged that in and it worked for awhile and cut out.
    Here's what I think after reading about another post with the same problem.
    The Cliff Jack does not have UK on it and according to a poster it should have.
    The other thing I noticed when I touched the speaker lead plug was that it had a sizzling vibration to it????
    NOW - At our practice shed I usually have a Buggera valve amp on the Marshall box and the Marshall head sits on the Buggera head. During the gig the Marshall head was sitting on the Quad box. Could it just be vibration or does the amp go into some sort of occilating space and just dies???? I know that sounds corny. If I replace the Cliff Jacks with something better I think that MIGHT solve the problem but with so much crap out now how do you really know??

    This problem has been with this amp for about 9yrs now with two techs not able to fault it and yet it occasionally drops out.
    I can't get past the Marshall sound and probably don't really want to. Even the Bugera sounds a bit sad next to it. Any ideas please???
     
    Last edited: Dec 4, 2019
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  2. marshallmellowed

    marshallmellowed Well-Known Member

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    Are you sure it's not something with the cab? Is this happening with the same cab, or different cabs?
     
  3. Ivor Carter

    Ivor Carter New Member

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    Hi! Thanks for the reply. No it's not the cab. Over the last 9 yrs I have modified the cab for different reasons in an effort to fix this issue. It's a 1960 cab. I have taken off the original plugging system and replaced it with old style Jacks. I actually only play through two speakers at any one time so that I can run another amp through the other two. I did this originally to cut the volume down a little as people were saying I was too loud.
    Either way it works for me. The tech swears black and blue that there's nothing wrong with the cab or the amp even though it still cuts out.
     
  4. marshallmellowed

    marshallmellowed Well-Known Member

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    Hard to say, obviously a bad connection somewhere, could be a jack, solder joint, relay (being a JVM), or failing tube.
     
  5. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member

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    Good luck on finding the culprit
    :welcome: To the forum
    Mitch
     
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  6. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    The Cliff Jack does not have UK on it and according to a poster it should have.

    This is a fake cliff jack which is known to fail.

    Plug a guitar cable between send and return, no effects.
    Then re-test the amp.

    Intermittent failures are the hardest to solve.
     
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  7. marshallmellowed

    marshallmellowed Well-Known Member

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    If you're looking for troubleshooting advice, you really need to give a full description of your rig. Are you running pedals in front of the amp, or in the loop? The first step in troubleshooting any amp is eliminating all external devices (guitar straight into amp, amp straight into cab, loop bypassed or jumpered...).
     
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  8. Ivor Carter

    Ivor Carter New Member

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    Thanks!
     
  9. Ivor Carter

    Ivor Carter New Member

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    Thanks. Yeah running a pedal board in front of the amp. It's failed before with nothing in front added.
     
  10. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    Bypass the effects loop first with a cable from send to return.
     
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  11. Ivor Carter

    Ivor Carter New Member

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    That's a great idea thanks - I'll give it a try. Problem is, now the amp is working just fine????
    Band Practice tonight so I'll see how it goes.
     
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  12. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    When the amp cuts out, connect the cable between send and return. Disconnect all the effects.
    Then play the amp and check if it cuts out again.
     
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  13. Micky

    Micky Well-Known Member VIP Member

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    Change out the speaker jacks and be done with it.
     
  14. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Yes, do that. Put in a new genuine Cliff jack and a brand new speaker cable with a SWITCHCRAFT plug on it. Accept no substitutes.

    I have found that even Neutrik can't make a 1/4" plug right. Which I was very surprised to discover. Switchcraft for 1/4" plugs. The only other brand I'll use is George L's stuff. But that's specialized for pedalboard wiring.
     
  15. marshallmellowed

    marshallmellowed Well-Known Member

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    This statement seems to be what some are primarily focusing on, and I'm not even sure what it means. Are you saying you took the chassis out of the amp, and after carefully looking at the jack, could not find a "UK" marking on the jack?
     
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  16. marshallmellowed

    marshallmellowed Well-Known Member

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    I guess what I should have asked is, has the amp "cut out" when using a different cab, or has it always been while using the same cab? You can't totally rule out the cab, unless the issue has occurred with more than one cab.
     
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  17. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    The market has been flooded with knock off jacks.
    These jacks are unreliable and should be avoided.

    The REAL Cliff Jack says: "Cliff UK."
    The FAKE Jack does not say "U.K!" That's how you can spot it.
    [​IMG] This is a REAL Cliff Jack. Says "U.K."

    [​IMG] This is the FAKE Cliff Jack.

    The REAL Cliff jack is made from Nylon, quite rugged and reliable.
    Lasts "almost" forever.
    The plating on the contacts is very high quality and durable.

    The FAKE jack appears to be made from polystyrene plastic, cracks quite easily, flimsy and easily broken.
    The plating on the contacts IS inferior, reports of failures are quite frequent.
     
  18. marshallmellowed

    marshallmellowed Well-Known Member

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    Yes, I know about the jacks themselves. What I was saying is, that I was unsure of what the OP meant, and if he actually removed the chassis to look for a "UK" marking on the jack(s), or if he was "assuming", without actually verifying. Bottom line, if it hasn't been verified that his JVM has an inferior speaker jack(s), the advice to replace the jack(s) is a bit premature.
     
    Last edited: Dec 4, 2019
  19. pedecamp

    pedecamp Well-Known Member

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    Sell it and get another one, they are fairly inexpensive used. :shrug:
     
  20. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    It could be the jack, the soldering on the board where the jack is, the cable, or the plug on the cable...
    Any of those things is a potential failure point.
    It could be the speaker itself also.

    I mentioned the effects loop bypass because that fixed 1 other 205h that was cutting out, and also reminded me that the unit may have the inferior jacks (especially if it's made in China, etc...)
    The units produced outside UK may be using the knockoff jacks.

    I also spotted these knockoff jacks in a Suhr Badger amp for the effects loop.

    The manufacturers may not realize that they are using the knockoffs. They may think they are using real Cliff jacks when they build the units.
     
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