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unidentified PT, how to establish what wire is for what...

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  • unidentified PT, how to establish what wire is for what...

    hi all,

    I've got a 120w PT that is the same as those used in the first Ashdown guitar amp heads that came out maybe 5 years back. Trouble is, I don't have a wiring diagram for it.

    What is the method for establishing whats what ???

    I've identified the wires that're on the same winding with a continuity test and also measured the resistance between the wires.

    PRIMARY (I think so anyway)

    * white (connected to nothing else)

    * black-green: 1.5ohm (0v-120v)
    * black-yellow: 4.1ohm (0v-220v?)
    * black-red: 4.7ohm (0v-240v?)
    * black-blue: 1.4ohm (0v-110v?)


    SECONDARY (hopefully)

    * green-green: 0.3ohm (heater winding, end to end?)
    * green-yellow: 0.2ohm (heater CT?)

    * purple-purple: 2.4ohm (winding for relays?)

    * black-blue: 11.9ohm (bias?)

    Does this look right?
    HTH - Heavier Than Hell

  • #2
    its ok folks, I got this sorted.
    HTH - Heavier Than Hell

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    • #3
      I'm assuming this is for a tube amp, since you referenced "heaters."
      Have you already identified the HV B+ secondary, or is it possible that it's mixed up with your primary connections?

      You could feed 6.3 vac INTO the two heater taps and measure your primary voltages. Use due caution!

      Nathan

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      • #4
        Whoops. Logged out, logged back in again and you had it sorted! Well done!

        Comment


        • #5
          Originally posted by octal View Post
          I'm assuming this is for a tube amp, since you referenced "heaters."
          Have you already identified the HV B+ secondary, or is it possible that it's mixed up with your primary connections?

          You could feed 6.3 vac INTO the two heater taps and measure your primary voltages. Use due caution!

          Nathan
          thanks Nathan, I ended up doing exactly what you suggested - feeding 6.3vac into the heater winding. I was 90% certain of the taps before this with the resistance measurements I took, but I had to know.

          a mate of mate suggested putting the 6.3vac through the primary and that does seem like a good suggestion - its way less voltage than the primaries are used to taking, so no fear of toasting anything.
          HTH - Heavier Than Hell

          Comment

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