tweed amp static on bass notes - interesting solution

Discussion in 'Amp Tech Center' started by jhundt, Apr 8, 2019.

  1. jhundt

    jhundt Doctor of Teleocity

    Age:
    65
    Posts:
    11,313
    Joined:
    Mar 23, 2003
    Location:
    Netherlands
    I built a Vibrolux 5f11 replica from a Mojo kit. Sounds great; good kit, I'm very happy.

    Recently I started getting a "static" sound, a sort of low crackling when I played low notes.
    With no guitar plugged in, or with a guitar turned down, there was no such sound.
    When I played the low notes, I noticed that touching the chassis around the control panel area would stop the sound.
    I took the back panel off and did some random chop-sticking and poking around, suspecting a poor solder joint somewhere. No crackly sound to be found.
    Then I noticed this:

    the chassis in these tweed amps is suspended from the top of the amp, hanging on two screws.
    the back panel, screwed into the cleats on the back of the cabinet, is lined with a metallic foil to serve as a shield for the open side of the chassis.
    On my amp, the chassis was just a tad too far forward, and was not making contact with the metallic foil on the back panel.
    But the chassis mounting screws were just a bit loose, so when a low note was played the vibration caused the bottom edge of the open-back chassis to make intermittent contact with the back panel, causing an audible crackling sound.
    Repositioning the chassis and tightening the mounting screws to insure good contact with the back panel solved the problem, and even gave a slight improvement in extraneous noise by completing the shielding.

    I was happy that the problem was so easy to solve, and I realized that on another day I might not have stumbled upon the answer so quickly. I might have spent hours trying to troubleshoot an electronics problem that didn't exist... wouldn't have been the first time, either!
     
    Last edited: Apr 8, 2019
  2. max_twang

    max_twang Tele-Afflicted

    Posts:
    1,383
    Joined:
    Nov 8, 2009
    Location:
    New York
    Nice problem solving!
     
  3. Fluddman

    Fluddman Tele-Meister

    Posts:
    157
    Joined:
    Apr 30, 2010
    Location:
    Sydney, Australia
    Well spotted sir! Crackles can often be difficult to track down.
     
  4. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

    Posts:
    6,326
    Joined:
    Jan 2, 2007
    Location:
    Beaumont, CA
    My Cox Ultimate 5e3 came with several 1" pieces of velcro (the fuzzy side) stuck tot he chassis to cushion the back panel and keep it from rattling. My amp is quite quiet, but I've wondered about the electrical connection to the shield.... My other two tweeds do not have any cushioning, but both have shielding in place and I made sure the Chassis was up tight tot he back panel!
     
  5. trouserpress

    trouserpress Tele-Holic

    Age:
    56
    Posts:
    521
    Joined:
    May 4, 2015
    Location:
    Leipzig
    I recently encountered the same symptoms with a Vibrochamp. Low notes caused the shunt on the replacement switchcraft speaker terminal to intermittendly touch the tip. I could not figure out how to properly solve this and I finally removed the shunt for good.
     
  6. jhundt

    jhundt Doctor of Teleocity

    Age:
    65
    Posts:
    11,313
    Joined:
    Mar 23, 2003
    Location:
    Netherlands
    there are so many crazy little things that can cause problems - problems that don't show up in the normal trouble-shooting guides. That is precisely why I posted this. Often the problem is much less serious than we think.
     
    Axis29 likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.