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ANOTHER dead valvestate !

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  • #61
    e / b /c

    tr4 -35 / -34 / -35

    tr7 +26 / +41 / +41

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    • #62
      Um...

      How can you have +26 on the emitter of TR7, with +41 on the other two TR7 is an MPSA56. Looking at the flat front face, the legs are left to right E-B-C. I am made to think EITHER you are reading the legs in the wrong order, OR the transistor is in backwards. ANy possibility of that?

      The fact you have about -35 on all three sides of TR4, and +23 or more on all the legs of TR7 tells me that the circuit through TR9 is either open or the transistor is not conducting. Oh wait, TR9 is missing?
      Education is what you're left with after you have forgotten what you have learned.

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      • #63
        they are on the board right--maybe i read them backwards...emitter and collector .

        yes TR9 is out of the pcb right now

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        • #64
          TR9 & 10 are out of circuit.
          You really should complete the path.
          1K resistor on TR9 & 10 base to emitter connections should do it.

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          • #65
            The way that TR7 & TR4 are biased, they should barely be On.
            Meaning the collector voltages of both should be very, very low.

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            • #66
              ok--ill try installing the 1k res tonight and report back---thanks !

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              • #67
                ok...

                tr8 still in.....9 and 10 out . 1k res installed as said.

                readings b / c /e

                tr8 +26v / +41 / +40

                tr9 holes +10 / +26 / +5

                tr10 +6 / -41 / +40

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                • #68
                  TR7 & TR 4 are most likely bad.

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                  • #69
                    put the 2 chips in , replaced tr4 / tr7 .

                    powered on with the limiter in place = still has a short-no change

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                    • #70
                      So what changed?

                      Before the most recent parts replacement (TR7 & 4) you had the amp off of the limiter.
                      Correct?
                      And you had the 1K resistors installed (to prove out the voltages)
                      And you did not have a short.

                      Personally, I don't know why you reinstalled the output transistors, as of yet.
                      The last go round showed a very high voltage on the bases.
                      Not good.

                      What gets me is where is the current going.
                      There is not a load hooked up is there?

                      You have to get off the lamp limiter.

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