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Marshall PT current ratings

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  • #16
    Originally posted by Helmholtz View Post
    A separate heater transformer may induce hum. It should be mounted at the outside/on top of a steel chassis and preferably have endbells and/or a copper flux band. Also its orientation may matter.
    Thanks, that’s good to know. The top of the amp is steel so I’m good there. Can I add a flux band by wrapping a turn of copper foil around the core in the winding direction?

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    • #17
      Can I add a flux band by wrapping a turn of copper foil around the core in the winding direction?
      I would think so. Just make sure that the foil is not too thin and is well soldered across its width to provide a perfect shorted "turn".
      - Own Opinions Only -

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      • #18
        Just a little update: I tested the heaters with all tubes inserted and no load on the HT, I’m getting 6.5V so I think I’m good voltage-wise. A little high since I have 230V on the 220V primary, but it will probably drop a bit when I connect the rest of the circuit. I’ll just keep an eye on the temperature, but I think this will work out.

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        • #19
          So if you were on a 220V outlet that would be about 6.22V. This stuff is rarely exact but if we take the numbers at face value that's a drop of only .08V. So yeah, I'd say you're probably good to go.
          "Take two placebos, works twice as well." Enzo

          "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

          "If you're not interested in opinions and the experience of others, why even start a thread?
          You can't just expect consent." Helmholtz

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          • #20
            just power it up with the Marshall PT and see what you have for filament voltage

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            • #21
              Originally posted by wamisur View Post
              just power it up with the Marshall PT and see what you have for filament voltage
              If the filament winding drops way below 6.3V, you'll know it's being stressed too much.
              Last edited by big_teee; 09-06-2022, 07:16 PM. Reason: Deleted Spam link, that was hidden by text color change.

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              • #22
                I think you can use your PT provided it runs cooler than in the original Marshall amp.

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                • #23
                  This stuff is rarely exact but if we take the numbers at face value that's a drop of only .08V. So yeah, I'd say you're probably good to go. i
                  Last edited by big_teee; 09-06-2022, 07:37 PM. Reason: Deleted hidden spam link.

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                  • #24
                    This thread is from 2020.
                    - Own Opinions Only -

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                    • #25
                      Originally posted by Helmholtz View Post
                      This thread is from 2020.
                      They are posting very credible messages with invisible spam links. They probably come back later and make them visible.
                      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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                      • #26
                        Originally posted by g1 View Post

                        They are posting very credible messages with invisible spam links. They probably come back later and make them visible.
                        And I'm watching for that. I did look up IP locations already and there's nothing obviously spammy about them, yet.
                        "Take two placebos, works twice as well." Enzo

                        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                        "If you're not interested in opinions and the experience of others, why even start a thread?
                        You can't just expect consent." Helmholtz

                        Comment

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