Jvm410h Power Supply Makes Strange Noises

Discussion in 'Marshall Amps' started by Markus6363, Jul 11, 2018.

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  1. Markus6363

    Markus6363 New Member

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    Hello Guys,
    I´m new here cause I was wondering what is going on with my JVM. Everytime I turn it on, and starts to hum unnaturaly loud and sometimes it even beginns to produce high frequency noises. I´m not sure what to do - is this a serious issue, or something I can leave it as it is ? Thanks in advance
    best regards Markus
     
  2. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Hello Markus. Welcome.

    Tell us more. Did you purchase new? When, as in under warranty?

    What you are describing does not sound good but answer some questions.

    Are the GAIN and VOLUME controls turned up, where?

    Do you have a speaker cabinet connected with a speaker type cable?
    Is the connection appropriate for output impedance matching from amplifier to speaker cabinet?

    Is the sound coming from the speakers or directly from the amplifier? If from the amplifier, which transformer if able to discern?
     
    MonstersOfTheMidway likes this.
  3. marshallmellowed

    marshallmellowed Well-Known Member

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    As mentioned, you must first determine if the noise is coming from the speakers or the transformer(s). If it's coming through the speakers, you may have a power tube on it's way out. If you determine the noise is coming from one of the transformers, try the following...
    Remove the rear panel before you use it next time. Then, while using the amp, if you hear the noise, try placing your hand on the transformer to see if it dampens the noise. There is no voltage present on the transformer housing(s), basically the same as touching the chassis. However, watch out for hot tubes if the amp has been on a while. If the hum/noise changes when you place your hand on the transformer, it's just a mechanical noise coming from the stacked plates of the transformer. This can sometimes be eliminated by tightening the screws holding the plates together. My JVM transformer had some buzzing, which I cured by adding nylon washers to the transformer screws. If the noise does not change when you apply some pressure with your hand, it could be noise from loose transformer windings. There's not much you can do if the noise is coming from the windings, short of replacing the transformer. Noise coming from the transformer is usually just annoying, and not a sign of transformer failure.
     
    Last edited: Jul 11, 2018
    Yamariv likes this.

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