JVM 205H 50amp Cuts out during performance AGAIN!

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

  1. marshallmellowed

    marshallmellowed Well-Known Member

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    This is one of those threads that, IMO, lacks the necessary information required to effectively troubleshoot the problem. It turns into a fishing expedition (fishing for information). I typically make a graceful exit at this point. Carry on, and good luck...
     
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  2. ampmadscientist

    ampmadscientist Well-Known Member

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    Why don't you walk the OP through some tests to verify it?

    You know it would only take 10 minutes to go through all the stuff I mentioned above. Over the website granted it will take longer and always does.
     
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  3. Ivor Carter

    Ivor Carter New Member

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    No. It had Cliff on it but no UK. I still think I should de solder it and have a look underneath.
     
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  4. Ivor Carter

    Ivor Carter New Member

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    Yes always the same cab but I've used other amps on this cab with no issues.
     
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  5. Ivor Carter

    Ivor Carter New Member

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    Do you mean sell the amp? If so could not do that with a clear conscience.
     
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  6. Ivor Carter

    Ivor Carter New Member

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    I won't know for sure until I take the jack out and look underneath for UK if it hasn't got it my question would be what is an amp made in the uk doing with inferior parts?
     
  7. scott-colorado2016

    scott-colorado2016 Active Member

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    It "sounds like" to me, an issue with the speaker jacks (based on info you've given). I would say 9 years of plugging in and unplugging cables will have an effect on a 1/4" jack. I say, get the speaker jacks replaced, sounds like the likely culprit.
     
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  8. Ivor Carter

    Ivor Carter New Member

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    It actually started soon after I bought it new. The amp failed dismally with a crook valve in the first week. It's been a bit of a lemon from day one but i love the sound but it's been embarrassing letting me down at gigs. Thanks for the reply.
     
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  9. scott-colorado2016

    scott-colorado2016 Active Member

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    Easy enough to change the jacks, especially if they are chassis mounted (as opposed to circuit board mounted). I don't know this amp, 5 jacks, a soldering iron, and some time may fix it. It's not unheard of to have a faulty part from a quality manufacturer, or a faulty solder joint from the factory. Maybe just a reflow on the solder connections to the speaker jacks, but I still lean towards a faulty jack.
     
  10. Micky

    Micky Well-Known Member VIP Member

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    Repeated use of the jack, including pulling or torquing of the plug while inserted in the jack can easily lead to cracked solder joints. Especially on the board-mounted jacks on newer Marshall amps.

    Best to inspect the jacks, or if you are uncomfortable working on an amp take it to a tech.
     
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  11. ampmadscientist

    ampmadscientist Well-Known Member

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    Well as I said, several manufacturers were using these fake jacks but didn't realize that they were knockoffs.
    You may or may not have the knockoff jacks.
    But what you do have is a connection issue it looks like.

    I have just changed all the fake ones since I found out what the difference was, in every amp I work on.
     
  12. marshallmellowed

    marshallmellowed Well-Known Member

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    What impedence is your cab? If your cab is 16 ohms, try running it on the 8 ohm output as a test. If the cab is 8 ohms, try running it on the 4 ohm output as a test. Running the amp in this manner, a slight mismatch, will not harm the amp, and will help narrow the troubleshooting. Just make sure you use the amp output that is "less than" the actual impedence of the cab (as I stated). If the amp still "cuts out", using a different output jack, it is unlikely that the output jack of the amp is the problem. If, when running the cab on a "different" output jack, the problem goes away, then the jack you "typically" use could very well be the problem.
     
    Last edited: Dec 6, 2019
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  13. Ivor Carter

    Ivor Carter New Member

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    Cab is 8 ohms the amp worked ok at band practice. Good idea though. I'm time poor at the moment just about to go Busking. This issue only happens once in a blue moon but usually during a gig!
     
  14. Ivor Carter

    Ivor Carter New Member

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    UPDATE.
    Well it's official! I have taken out the jack and found that the so called jack is not a real cliff jack and it was pretty flimsy falling apart when I took it out. Going to Adelaide today to try and find something that's made better.
    Thanks for all your help and suggestions.
     

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