isolating a chassis rattle in a Princeton Reverb

Discussion in 'Amps and Cabs' started by chrismalley, May 24, 2008.

  1. chrismalley

    chrismalley Member

    Messages:
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    May 11, 2007
    I have a 1971 Princeton Reverb, sounds great, recently overhauled. But if I turn it up past 4, the chassis starts to "rattle" on low notes - not a pleasant sound. Speaker is OK, cabinet is solid, no loose components on the chassis, not a tube rattling, not the amp handle -- definitely the chassis.

    Does anyone have suggestions for how to isolate the chassis from the cabinet? Is there a kit available for this type of thing?...

    Thanks!

    Chris Malley
    www.chrismalley.com
     
  2. FFTT

    FFTT Member

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    You might try those semi-hard rubber washers from a plumbing supply
    store.

    Also check to make sure none of the components are resting against the inside of the chassis.

    Check name plates, knobs and switches to make sure they are properly secured as well as the speaker mount screws.
     
  3. alltone

    alltone Member

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    Huntsville, Ontario, Canada
    Also...transformer mounts...filter cap cover pan..loose pot nuts...loose set screws on control knobs.. tube sockets...
    anything that is bolted or screwed down to the chassis???!!:munch
     
  4. chrismalley

    chrismalley Member

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    Thanks for the replies and suggestions.

    Here's the solution I came up with, in case anyone is interested...

    Materials needed:
    - about 2' of 1/8" thick x 3/4" wide rubber weatherstripping (for doors and windows) with adhesive backing
    - four #12 rubber grommets
    - four washers about the same diameter as the grommets

    Procedure:
    (1) Pull the chassis out of the cabinet. Check anything that could possibly be loose (as others have suggested in this posting).

    (2) Cut eight 3" strips of weatherstippping. Stick them at the corners and centers on the top edges of the chassis. This dampens vibrations between the top of the chassis and the cabinet.

    (3) Place the chassis back in the cabinet. Insert the chassis mounting bolts, but don't install the lock nuts yet.

    (4) For each mounting bolt, put on a rubber grommet, followed by a flat washer, followed by the lock nut. The rubber grommet isolates the bottom of the chassis from the mounting bolt. The flat washer keeps the lock nut from tearing up the rubber grommet, and compresses the rubber grommet evenly as the lock nut is tightened.

    (5) Tighten the lock nut, but not too tight -- you don't want to compress the weatherstripping and grommets too much, or you'll loose some of the dampening. Tighten it just enough so that the chassis doesn't flop around in the cabinet.

    This worked like a charm. No mods required, all easily reversible. The chassis is well-seated in the cabinet, and it doesn't move around at all. If you look very closely, you can barely see the weatherstipping. Most importantly, the rattle is gone, and I can crank 'er up!
     
    dustinhofsess likes this.
  5. riker4208

    riker4208 Member

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    sweet thanks chris
     
  6. dustinhofsess

    dustinhofsess Member

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    Charlotte, NC
    Chris this solution worked great for me. I was pulling my hair out looking for a chassis rattle and I came across this old thread. What a simple and elegant solution. Thanks!!
     

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