Custom Vibrolux Reverb: Turning On Problem

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by schmidlin, May 3, 2015.

  1. schmidlin

    schmidlin Member

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    Client brings this amp over saying it
    1: Sometimes turns on
    2: Sometimes doesn't turn on
    3: Sometimes turns on after ten minutes of turning it on.

    Sure as shootin' I have experienced all three. Here's the odd part: when he brought it over, it didn't turn on so I just left it that way for a couple hours just to see what happened. It never came on so I go for dis-assembly and notice that the PT is warm. Odd. I check the pilot lamp and mains fuse and both check OK. Chopsticks too.

    So far, now it comes on every time. My only guess is that the inrush current limiter (NTC) is faulty, but I have no experience with how those go bad. Any suggestions? Do I need to say how much I hate intermittent problems?

    http://el34world.com/charts/Schematics/files/fender/Fender_custom_vibrolux_manual.pdf
     
  2. Tony Bones

    Tony Bones Member

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    You've got a volt meter right? See what's working and what's not working. The problem will be in between the working part and the not working part.

    This is basic troubleshooting procedure.
     
  3. schmidlin

    schmidlin Member

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    Yeah, I know. I just can't get the dumb thing to act up again. Been trying all day....
     
  4. mark norwine

    mark norwine Member

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    unplug it, and check continuity of the power cord while wiggling the plug.

    These have cheap cords.....and people love to unplug things by yanking the cord. An intermittent plug will do what you're seeing.
     
  5. schmidlin

    schmidlin Member

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    Yeah, the first thing I did was wiggle the cord. I'm pretty sure this was a loose lamp. When it "wasn't working" I forgot to check if the tubes were glowing. I've been flipping thing on and off all day.

    PSA kiddies: don't trust your pilot light, and no this isn't the first time this has happened to me.
     
  6. Steppin' Wolfe

    Steppin' Wolfe Member

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    Yeah, I have never seen a pilot light process any signal...so if a good bulb in that socket doesn't glow, I look at the tubes and voltages.
    +1 with Tony on this one. IF the PT was warm, it was being worked---hopefully properly... by current going through a circuit to some extent.
     

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