LabSeries L7 Guitar Amplifier RFI Fix

I picked up a 1977 LabSeries Guitar amp and it picked up radio stations as if it were designed for it. This is how I fixed it.

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I picked up a 1977 LabSeries guitar amp from a local pawn shop, while I was there it sounded great! However when I got home and turned it on a local radio station came through loud and clear. I find nothing more annoying than trying to jam out while some advertisement comes through attempting to be a "Backup band."

This is a very simple fix for this sort of issue.

I made a video showing where I had to cover with tape in order to shield out the radio interference.  Hope it helps :)

  • 1 × Copper tape I used a "chemical free" slug and snail tape. It is made of copper and has a nice adhesive backing
  • 1 × A small piece of wire Or you could simply make sure that you have another way to ground the copper tape.

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  • 1
    Step 1

    The tricky part about this is you have to find out what part of the amp is acting as an antenna.  In the case of this amp, it was the wire that ran from the amp head down to the reverb tank.  I found this first by using some cheap aluminum foil.  

    With the foil grounded via a wire to the amp chassis, simply move it around the amp to pinpoint the location that is picking up the signal.  

  • 2
    Step 2

    After you find out the side that is causing the problem, wrap the offending wires with the foil.  This creates a makeshift shield as long as the foil is grounded to the chassis

  • 3
    Step 3

    If you want to keep the amp original, and not replace wire, you can leave this foil in place.  This is fine as long as the amp isn't really moved.  However, if you move the amp around you will want to replace the foil with something a lot better.  I chose "Slug and Snail" tape as it was a tenth of the price when compared to the copper tape that music stores sold.

    If you don't mind replacing wire in the amp, you could pick up some shield wire and replace it, remembering to connect the shield to a ground.  

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Chris wrote 04/02/2021 at 20:01 point

Thanks, I have the same amp and this was driving me nuts.

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Eric Evenchick wrote 05/04/2014 at 09:06 point
You can embed videos in project logs by pasting the link.

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ThunderSqueak wrote 05/04/2014 at 18:05 point
Thanks, just wish you could also embed them into the project description. :(

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