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Polytone 100 - power amp issue

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  • #16
    These are new output transistors (Q6 & Q7)? The original ones measured bad (post #1).
    If Q3 does not measure bad I would not replace it.
    For Q4,Q5, I would use something like TIP41 and TIP42, but you will have to adjust the placement if different pin-out.
    Originally posted by Enzo
    I have a sign in my shop that says, "Never think up reasons not to check something."


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    • #17
      Originally posted by g1 View Post
      These are new output transistors (Q6 & Q7)? The original ones measured bad (post #1).
      If Q3 does not measure bad I would not replace it.
      For Q4,Q5, I would use something like TIP41 and TIP42, but you will have to adjust the placement if different pin-out.
      No, all transistors were tested outside PCB, and tested good.
      I used DCA55 Atlas tester and diode tester additionally, just to confirm results.

      I have no idea what is causing Q5/Q7 to open.
      Voltages at bases (bias) of both drivers are different, clearly at Q5 is higher…

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