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New Hot Rod Deluxe Problem

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  • #1

    New Hot Rod Deluxe Problem

    Ok, so I have fixed a bunch of HRDs but this one is stumping me. It is basically switching channels fine and all but there is NO volume except very slightly. You can plug into the loop and still the same thing. I tested all of my power coming off of the PT and all if fine but tracing back from the power tubes I noticed that both of my coupling caps are passing DC. Anybody have any ideas?? They are the .1 Phase inverter caps.
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  • #2
    How much DC?

    Out of interest what are your PI plate voltages?

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    • #3
      Originally posted by MWJB View Post
      How much DC?

      Out of interest what are your PI plate voltages?
      I'll have to check again when I get home today but I know I am leaking 40VDC through both caps.

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      • #4
        tracing back from the power tubes I noticed that both of my coupling caps are passing DC. Anybody have any ideas?? They are the .1 Phase inverter caps
        Are you sure that's not the grid bias voltage?

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        • #5
          The power tubes should be red plating if your leaking DC because it will drop the grid bias towards zero and the tubes or tube will start conducting current heavier. Monitor the bias on pin 5 and see what happens after a minute or so. Also try patching a cable from the send jack to the return and see if it comes back.
          KB

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          • #6
            Another way to echo what Jag and AmpKat are saying is, are your sure that 40V isn't negative? -40V on the power tube grids is good. +40V is very, very bad.

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            • #7
              And +40 is very unlikely on BOTH sides of this amp.

              Have you subbed the preamp tubes?

              First then after that would be start checking the plate and cathode voltages at each preamp tube.
              Education is what you're left with after you have forgotten what you have learned.

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              • #8
                Originally posted by Don Moose View Post
                Another way to echo what Jag and AmpKat are saying is, are your sure that 40V isn't negative? -40V on the power tube grids is good. +40V is very, very bad.
                Yeah man you were right. It was -40vdc. Didn't even notice. lol Why is there -40 there anyway? Also to give an update I FINALLY figured it out. I put a signal through the input and started tracing and ended seeing a crack in the trace on both sides of C23. Amp is kicking now.

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                • #9
                  That -40v is your bias voltage.
                  Education is what you're left with after you have forgotten what you have learned.

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