1965 Vibrolux

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by sdlogan9, Feb 14, 2015.

  1. sdlogan9

    sdlogan9 Gold Supporting Member

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    Hey guys


    I have a customer that has a 1965 Vibrolux.. He called me on the phone and gave me the symptoms he is experiencing and told me he would bring it by on Monday for me to take a look.

    Here is what he told me over the phone.

    1. He has been using an Ultimate Attenuator for a few years when he gig's the amp.

    2. He uses a 1966 Gibson es 345 and he runs the amp in stereo from the stereo output's of the guitar. clarification - " I am sorry I did not make this more clear in the first post.

    I believe what he is doing is using a Y cable off the stereo jacks of the guitar and running it into just the Vib/Reverb channel "



    3. He said for the past several gig's his amp(Vibrolux) has a significant volume loss on the " Right " channel " Reverb/Vibrato side. He has he needs to turn the amp up to 7 or 8 to get noticeable sound.

    4. He says that the left channel works perfect and is very loud.

    what is your general idea's about what the problem might be?

    -Shane



     
    Last edited: Feb 17, 2015
  2. Jeff Gehring

    Jeff Gehring Silver Supporting Member

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    Running into both channels of a Vibrolux Reverb is a little problematic in that the channels are opposite polarity due to one extra inverting gain stage in the Vib/Trem side. You will get some cancellation running the same signal into both channels.

    Check the tubes for the vib/trem channel (I think V2 and V4). Otherwise, the first two triode stages are the same design for the normal and vib/trem sides, so you should be able to see comparable gains/levels between the two of them for similar vol/tone settings. If the channels act the same up to the outputs of the volume control recovery stages, but the vib/trem is still weak overall, that would tend to point to the pins 6,7,& 8 side of V4 having some sort of problem.
     
  3. twangbanger

    twangbanger Supporting Member

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    What Jeff said , I can't imagine running both channels together would sound good at all due to the phase cancellation. Is this something he just started doing and might be causing the problem.
     
  4. zenas

    zenas Member

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    I'm sorry but I have to ask how long you been in the amp repair buisness? This is a Fender blackface probably the easiest amp on the planet to work on and it's only having a problem on one channel. It's either v2, v4 or something pretty simple that'll take less than a half hour to fix like a bad solder joint, maybe a cooked resister or possibly a bad electrolytic.

    Again I'm sorry to ask but your running an amp repair buisness and that's somebody's 2000 dollar plus amp.
     
  5. Don A

    Don A Silver Supporting Member

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    I don't think that's an issue when using an ES-345 with that amp. The ES-345 is a stereo guitar and I believe the outputs are out of phase with each other.
     
  6. sdlogan9

    sdlogan9 Gold Supporting Member

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    Ok let me clarify

    I am sorry I did not make this more clear in the first post.

    I believe what he is doing is using a Y cable off the stereo jacks of the guitar and running it into just the Vib/Reverb channel

    -Shane
     
  7. DGDGBD

    DGDGBD Member

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    The problem is with the amp, so what does it matter what kind of guitar's being used?
     
  8. sdlogan9

    sdlogan9 Gold Supporting Member

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    Dosnt matter - just giving what info I have ATM

    -Shane
     
  9. jay42

    jay42 Member

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    If it's not a preamp tube, then you want to pull the output tubes and run a sine wave into it. Some stage is not going to work right. Could be in the tone stack or a badly drifted cathode resistor...dead cathode cap(s)...clearly, it's good at the phase inverter and beyond.
     
  10. sdlogan9

    sdlogan9 Gold Supporting Member

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    Video Added!

    At about 35-40 seconds in to the video you can hear how the amp just instantly cuts volume level.

    This is an intermittent thing it seems to cut in and out randomly

     
  11. Blue Strat

    Blue Strat Member

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    Normal routine:
    Check tubes, check bias, check voltages and go from there.
     

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