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Twin Reverb AB763 PS Question

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  • Twin Reverb AB763 PS Question

    Can anybody speculate as to why the amp I'm working on has a jumper wire across the 1K resistor for node "C" in this amp? (circled in attached pic)

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    "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

  • #2
    No other changes? MAybe they wanted a few extra volts up front?
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      That's the only thing I could come up with myself. My customer just bought it and wants it gone through and checked out. It's obviously had some work done. There are some new screen resistors and it's been recapped. I don't think he wants any mods. He bought it for what it is supposed to be. I'll probably remove the jumper. I was just seeing if anyone has encountered this before as I've never seen it done. I was checking out the doghouse components and was reading a short across the resistor. It didn't make any sense and took me a bit to find the hidden jumper on the underside of the board.
      "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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      • #4
        Underside of the dog board?

        Consider this then. WHen I install new caps, there is a lot of excess lead length. So on the ground end, I will bend one over to the next eyelet, rather than use a separate piece of wire. Any chance some one did this by mistake, happening to short your resistor? I hope that description was clear.
        Education is what you're left with after you have forgotten what you have learned.

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        • #5
          I was just working on the amp. I lifted the dog board to remove the jumper. It was long cap leads bent over to the next eyelet. I was just coming back here to post that exact thing and you beat me to it. I do believe someone did this in error and I have to wonder how long it's been like this. There is evidence of some other "not so well done" work in the chassis. The amp is going to need a thorough going through. Oh, and your description was clear to me because that is exactly what I found.
          "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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          • #6
            I aim to please.
            Education is what you're left with after you have forgotten what you have learned.

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