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Fender FM 65

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  • #16
    Got it ---thanks---ill report back when i get one

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    • #17
      Ok , what is the acceptable temp range on these transistors ?? Somethings still not right (i think? )

      Amp is powered up--no bulb limiter , no output load .

      Just replaced Q17 / 6 /8 .

      The temp is creeping up to over 95 before i shut it off on Q 11 , Q 15/17/18/19 .

      Everything else is at 66-70 degrees . There is no Dc at the speaker out . The bulb is dark now if i use the limiter even with a load on output

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      • #18
        Forgot to add = voltages look normal now at the 4 output chips

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        • #19
          Originally posted by Valvehead View Post
          The temp is creeping up to over 95 before i shut it off on Q 11 , Q 15/17/18/19 .
          95 what?
          95°C would be excessive. 95 degree Fahrenheit corresponds to 35°C and should be no problem. Semiconductor temperature tends to get critical, when it's too hot to touch (above 50°C to 60°C).

          - Own Opinions Only -

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          • #20
            95 F and creeping up.

            Im just asking because i dont want to see magic smoke come out of this thing

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            • #21
              Are all transistors bolted to heatsink and all heatsinks completely assembled to chassis? What are your DC voltages across R103 and across R105 ?
              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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              • #22
                Originally posted by g1 View Post
                Are all transistors bolted to heatsink and all heatsinks completely assembled to chassis? What are your DC voltages across R103 and across R105 ?
                I didnt think of that...the pcb is out of the chassis. Ill put it back in and check

                r103 / r105 , 4mv and 10mv to gnd

                Edit----good call G1 , amp is back together and everything looks stable now....will try it tonight
                Last edited by Valvehead; 04-21-2021, 04:48 AM.

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                • #23
                  Amp is up and running , sounds great -- thanks everyone !!!!!

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