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Smokin' Vibro Champ!

Discussion in 'Amp Central Station' started by mistermullens, Mar 24, 2015.

  1. mistermullens

    mistermullens Poster Extraordinaire

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    Literally! Cranked up the ol' 76 Vibro Champ about a month or so ago, made a weird staticy sound, then smoke started coming out the inputs. Finally got around to looking at it. All the tubes light up, but the 5Y3 tube isn't very bright. Seem lacking, but I'm not in the habit of looking at the tubes when the amp is working. Pulled the chassis, and nothing is burned. Think it could just be the tube? Any other thoughts?

    P.S. I usually take it to Andrews Amp Lab, but I'd like to avoid the cost of having it worked on if possible. Then again, I'll do it if its more than a tube swap.
     

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  2. keithb7

    keithb7 Friend of Leo's

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    Get a chop stick and a magnifying glass. Look for toasty burn marks. Tubes are vacuum sealed and don't smoke. Resistors and capacitors are not. They get can get smoking hot. Sure hope your PT is ok. Do us a favour, pull the fuse tell us what amp rating it is.
     
  3. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    See anything odd when it's running? Sometimes a part that looks normal can still smoke during operation. If you have a light bulb limiter or something similar see what happens when you plug it in and fire it up. Make sure a speaker is connected while you work on it.
     
  4. muchxs

    muchxs Doctor of Teleocity

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    Letting the smoke out is never a good sign.

    Supply voltage is usually over 420 volts on these making them a torture chamber for Russian 6V6s. It may be in the process of melting the 6V6 and / or cooking the bias network.

    ...which IMO should be a 5 watt ceramic resistor instead of the stock 2 watt carbon comp.

    The "lights out!" trick is very effective on these. Remove the back panel. Crank the amp and plug in your guitar. Turn out the lights. If you see blue sparks inside the 6V6 accompanying your crackle the 6V6 probably has a problem.

    A shorted 6V6 may damage its cathode bypass capacitor. It won't fix itself.

    The TDPRI Georgia Vibro Champ Posse that includes jonrpick and andyfromdenver may be able to offer assistance a little closer to home.
     
  5. muchxs

    muchxs Doctor of Teleocity

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    "Dear Abby, Dear Abby, My amplifier broke! It let out a crackle and started to smoke..."

    .
     
  6. mherrcat

    mherrcat Tele-Holic

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    Perfect! Love John Prine.
     
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