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Transformer has no center taps?

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  • Transformer has no center taps?

    This is the power transformer I pulled from an old tube reel-to-reel unit:

    https://ibb.co/NT5TjK7

    Two wires for the primary, two wires for the HV secondary, two for the LV secondary. No center tap wires.

    Here’s the schematic (printed inside the unit):

    https://ibb.co/Kx5dNX0

    The PT is at the bottom, just right of center; you’ll note that it shows both secondaries have grounded center taps. So what gives? Are the center taps internally grounded? Is that a thing?

  • #2
    Is that a thing?
    Got an ohm meter?


    (Gotta bring along those Ann Arbor guys...)
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      I've seen power transformers with internally grounded center taps. You have to hope the mounting bolts don't come loose.

      Comment


      • #4
        Originally posted by Enzo View Post
        Got an ohm meter?


        (Gotta bring along those Ann Arbor guys...)
        Yeah I suppose I should have thought of that. It is indeed internally grounded. Seems like a lousy way to do it though. Makes the chassis connections really important.

        Too bad there’s no 5v tap, would actually make a decent PT for a low wattage tweed style amp.

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        • #5
          Originally posted by MikeH View Post
          It is indeed internally grounded. Seems like a lousy way to do it though. Makes the chassis connections really important.
          I'm a bit surprised seeing those 'clip on' nuts like that for the mounting. There's no external wire to the casing?
          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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          • #6
            And with enameled bell covers and base mount.?. I'd remove the covers and see what internally grounded means. If the internal ground contact is visible and it didn't satisfy me I'd add a lead that could be soldered.
            "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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            • #7
              Originally posted by g1 View Post
              I'm a bit surprised seeing those 'clip on' nuts like that for the mounting. There's no external wire to the casing?
              It may be under the bells, but yeah definitely seems like a sketchy ground connection. If I ever have the itch to use it I’ll take the bells off and see if there is a lead that is accessible.

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              • #8
                Originally posted by Chuck H View Post
                And with enameled bell covers and base mount.?. I'd remove the covers and see what internally grounded means. If the internal ground contact is visible and it didn't satisfy me I'd add a lead that could be soldered.
                Amen!
                "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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                • #9
                  "tinnerman nuts"
                  Education is what you're left with after you have forgotten what you have learned.

                  Comment


                  • #10
                    Originally posted by Enzo View Post
                    "tinnerman nuts"
                    Show off.

                    But really, that's cool. I use to work with a carpenter that knew the names for every type of trim appointment ever installed on a house. Who knows what an astragal is!?! It was fun.
                    "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


                    • #11
                      I know what an ogee is. Ooh ooh, and a finial.



                      OK, how about apse, nave, and narthex?
                      Last edited by Chuck H; 04-29-2020, 02:49 AM.
                      Education is what you're left with after you have forgotten what you have learned.

                      Comment


                      • #12
                        Originally posted by MikeH View Post
                        Too bad there’s no 5v tap, would actually make a decent PT for a low wattage tweed style amp.
                        Couple of diodes.. doubt if it would make a huge difference. If its out of a R to R it’s probably a single ended amp.

                        Comment


                        • #13
                          Originally posted by Enzo View Post
                          OK, how about apse, nave, and narthex?
                          Just nave with a K.
                          Originally posted by Enzo
                          I have a sign in my shop that says, "Never think up reasons not to check something."


                          Comment

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