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New vibrochamp speed issue

Discussion in 'Shock Brother's DIY Amps' started by Kev Reg, Apr 14, 2017.

  1. Kev Reg

    Kev Reg Tele-Meister

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    Having an issue with my new vibrochamp build. The intensity pot works fine although i could not find a 25k reverse log pot so I used a 50k linear pot with a 48k resistor across wiper and top.
    However I have no speed control at all. I have swapped tubes and also disconected and measured the 3meg reverse log pot and it functions as normal. What components should I check first? 20170414_200129.jpg 20170414_195943.jpg 20170414_195857.jpg hopefully something will jump out in these pictures.
     
  2. Kev Reg

    Kev Reg Tele-Meister

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    Quick update. With tremelo switch disengaged I can change the output volume of the amp. Full intensity lowers volume and zero intensity gives max volume. Possibly its down to modifications to the intensity pot. Im starting to wish I had just fitted a 25k or 50k reverse log pot instead.
     
  3. tele_player

    tele_player Tele-Meister

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    Looks like nothing is connected to center lug on speed pot. That's wrong. Connect center lug to the lug with the resistor to ground.
     
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  4. Kev Reg

    Kev Reg Tele-Meister

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    Wow you are right enough. I was looking at the triode layout and the link wire is so feint on the drawing you can hardly see it. Had to zoom in close. Its like a faded grey on white. Will try soldering link on tomorrow.
    Many thanks
     
  5. Kev Reg

    Kev Reg Tele-Meister

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    tempFileForShare.jpg Here is the drawing with faded link I was following.
     
  6. tele_player

    tele_player Tele-Meister

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    The thing to remember is that you'll never use a pot with no connection on center lug. The center lug is the wiper, and it's what distinguishes a pot from a resistor.
     
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  7. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Nice catch tele_player.
     
  8. Kev Reg

    Kev Reg Tele-Meister

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    I must admit im still have alot to learn :). I didnt know about the wiper and it makes sense now.
    This is my second build. First one was a 5e3 and it went like a breeze. This one not so much. I had an issue on startup where I was shorting my b+ straight to ground at the first filter capacitor. I had mounted them on tag board and didnt realise that the tag i had soldered to was bolted to the chassis.:eek: The rectifier looked like it was going to explode!. Im amazed the thing still functioned after that.
     
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