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Marshall mg100hdfx power chip

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  • #16
    Just wondering. Could any zener between 5.1 to 9.6 be used for d14 ? I know it calls for a 6.8 but waiting and the cost of ordering. i can get the others now

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    • #17
      Have you actually determined it is the zener that is bad, rather than the transistor or the cap? If the transistor is what is shorted, then we need not even worry about the zener.

      What is the closest zener you have?
      Education is what you're left with after you have forgotten what you have learned.

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      • #18
        Amp is working great been on 3 hours. No problem with a hot heatsink. "Haven't played it real loud yet: . Put a Radio Shack. 276-565 5.1 volt zener in . It reads 4.08volts on pin 4. That seems to just over the min rating from the datasheet. This is my 4th amp you guys have saved from the dump. Got some real winniers to work on next. Thanks Guys for the help. I would have had no idea.

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        • #19
          Originally posted by jessadr View Post
          Put a Radio Shack. 276-565 5.1 volt zener in . It reads 4.08volts on pin 4. .
          That is pin#9, right?
          The 'Standby' pin.

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          • #20
            Yes pin 9 on the chip goes to pin 4 on CON1 Boy this fan is too loud. Oiled it when it was out. Need to order a new fan I guess, or mod it and put in a big pc power supply fan.

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            • #21
              Originally posted by jessadr View Post
              Amp is working great been on 3 hours. No problem with a hot heatsink. "Haven't played it real loud yet: . Put a Radio Shack. 276-565 5.1 volt zener in . It reads 4.08volts on pin 4. That seems to just over the min rating from the datasheet. This is my 4th amp you guys have saved from the dump. Got some real winniers to work on next. Thanks Guys for the help. I would have had no idea.
              It's that bloody zener again....bloody zeners.
              The bigger fan running at a slower speed will have just as much cooling and less noise,
              but on this amp, it's harder to modify.
              Last edited by soundguruman; 07-05-2012, 05:49 AM.

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              • #22
                At least now we know a "shack" one will work in a pinch. Now on to the vs100 got to order new outputs. got sub numbers from enzo.

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                • #23
                  The zener is there to prevent the voltage from going over its value, not to establish a voltage. Usually it fails when the TDA7293 shorts out and sends the main power rail back down the standby line to it.
                  Education is what you're left with after you have forgotten what you have learned.

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