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Thread: electric hum

  1. #1
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    Default electric hum

    Full disclosure: this is not a mando post but I figured there would be folks here that would know the answer. I have a mid-70ís Ibanez pre-lawsuit Les Paul copy guitar that has been sitting in a closet unused for over 20 years. I decided to pull it out and start playing it again. I plugged it into the amp just to see if it worked. There was a tremendous amount of hum and the volume was very low. I changed the strings and plugged it back in. The hum was gone and the volume was back. Did something happen with the strings over 2 decades to cause this is was it a coincidence?

  2. #2
    Registered User Toni Schula's Avatar
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    Default Re: electric hum

    Likely this was coincidence.
    My guess would be a loose/poor contact somewhere in the electric path from the pickups to the amp...

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    Default Re: electric hum

    Likely to be socket corrosion - either in the guitar or the amp. Plug something in once and the corrosion gives you a bad earth, which causes hum and a decreased signal. The corrosion will likely wear away with reapeated pluggings. A squirt of switch cleaner and some mechanical movement with the plug will usually solve the problem. If not, you need to dismantle and attack the socket with something more abrasive.

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    Default Re: electric hum

    I plugging in and out with a cleaner doesn't cure it, I wouldn't use an abrasive. Doing so will make it happen more frequently. I would replace it.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

  5. #5
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    Default Re: electric hum

    Could be just the cable's internal connections. Try massaging it while powered up, you might hear intermittant static.

    (I once avoided mega-repairs on a '70 Pontiac, w/ over 100k miles, by messaging the wiring bundle until the engine stuttered. Sliced the bundle open, found the break ... a 20-minute fix!)
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    Default Re: electric hum

    Dirty pots on the guitar. Once you start fiddling with them, the dirt/corrosion clears off and the noise disappears. Still a good idea to disassemble and clean.
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  7. #7
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    Default Re: electric hum

    Thanks for all the comments. I ordered some DeoxIT spray to try to clean the jack.

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    Default Re: electric hum

    Good idea. It won’t do any harm even if that’s not the problem and one can should last most people a lifetime. I bought a can of Sevisol over 30 years ago - if only I could remember where I put it !!!!

  9. #9
    Innocent Bystander JeffD's Avatar
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    Default Re: electric hum

    An aside that my or may not be relevant. Sometimes this kind of thing happens when the third prong of the amp plug is not connected to the ground of the outlet, either because someone broke it off to fit in a two conductor extension chord, or because someone is using a three prong adapter plug as a cheater, (as opposed to converting a two pronged outlet to three, by connecting the ground connection on the back of the plug to the ground of the outlet.)

    Tech talk I know. Point is, if the amplifier uses a three pronged plug, it is meant to be connected to a three pronged outlet, and some of these hum issues are the result of not being strict about this. (If the safety argument for connecting the plug properly doesn't convince you.)
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    Default Re: electric hum

    Quote Originally Posted by JeffD View Post
    An aside that my or may not be relevant. Sometimes this kind of thing happens when the third prong of the amp plug is not connected to the ground of the outlet, either because someone broke it off to fit in a two conductor extension chord, or because someone is using a three prong adapter plug as a cheater, (as opposed to converting a two pronged outlet to three, by connecting the ground connection on the back of the plug to the ground of the outlet.)

    Tech talk I know. Point is, if the amplifier uses a three pronged plug, it is meant to be connected to a three pronged outlet, and some of these hum issues are the result of not being strict about this. (If the safety argument for connecting the plug properly doesn't convince you.)
    In this case I don't think that was my issue. The room where my instruments are only had one 3-prong outlet (my house is from the 1660's). So when I got the amp are changed out one of the 2-prong outlets with a 3-prong. After installing, I verified it was grounded with a continuity checker. Its been fine since that first time I plugged it it so I am fairly sure it was just a poor connection in the guitar jack.

  11. #11
    Innocent Bystander JeffD's Avatar
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    Default Re: electric hum

    Quote Originally Posted by DaveGinNJ View Post
    In this case I don't think that was my issue. The room where my instruments are only had one 3-prong outlet (my house is from the 1660's). So when I got the amp are changed out one of the 2-prong outlets with a 3-prong. After installing, I verified it was grounded with a continuity checker. Its been fine since that first time I plugged it it so I am fairly sure it was just a poor connection in the guitar jack.
    I wasn't sure, just thought everyone could benefit.
    Indulge responsibly!

    The entire staff
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