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  • #1

    Power Transformer

    Hi,
    I've got a Power Transformer here, no load just hooked up to the wall I have about 400 - 0 - 400

    7.3V Filament and
    5V on the well 5V.

    I'm expecting that this will drop to 300 0 300 under load.
    my plan is to use this for an AC 15, but I fear is going to be too high a B+ for a power supply with an EZ81 or is it?
    Tags: None
  • #2
    At 400-0-400 using an EZ81 your likely to get over 500Vp under load. Waaay too high for an AC15. I don't know what the mA rating is for your tranny but if it's big enough it could be used for 6L6gc/EL34/6550 type tubes.

    Chuck
    "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

    • #3
      This is the PT out of my filmosound, I'm wondering if I can drop the Voltage by going with differnt resistors in the power supply, and another rectifier. I don't think this will push 6L6's, as it's a 14W amp to begin with.

      I'd better get reading up finding one that doesnt have as much oomph, or getting a lower voltage PT.

      Comment

      • #4
        Hmmm...

        To get the 335Vp shown on the schematic (that you posted in a previous thread) your PT should be around 290-0-290. There's nothing unusual about that power supply so I can't imagine how 400-0-400 amounts to 335Vp.

        Chuck
        "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

        • #5
          Originally posted by Chuck H View Post
          Hmmm...

          To get the 335Vp shown on the schematic (that you posted in a previous thread) your PT should be around 290-0-290. There's nothing unusual about that power supply so I can't imagine how 400-0-400 amounts to 335Vp.

          Chuck
          Chuck,

          I'm scratching my head, I've got the Tranny out of the chassis, (which is gutted anyway) and just have 120 connected to it, and my voltage is 402 0 402 without being connected to anything.

          It looks old as the hills, so I'm pretty sure it's original.

          I just wonder if I put it in and give it a try, put a larger value resistor say 1.5K 2W or 2K and see if it drops the voltage to 315VDC which is where I'm wanting to be.

          Comment

          • #6
            What are the actual measured voltages on the other secondaries and your wall AC (you posted 120, 7.3V and 5V before, but I'd like to know these voltages very finite)?

            With the 6.3V tap reading 7.3 your wall volts should be around 127 (which isn't unusual at my place). Assuming this PT has a 110V primary. Under these conditions your 5V tap should read about 5.7V. But even with this scenario an HV secondary of 300-0-300 would read about 350-0-350, not 400-0-400. And a shorted primary wind resulting in 402-0-402 should make for higher volts on the other two secondaries... Hmmm???

            Chuck
            "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

            • #7
              OK... Looking at the schem again I see that you have a 5y3 rectifier tube and a 117V primary. Using Duncan PSU with a 5Y3 recto and simulating that amps current draw (load) I get 330-0-330 for an HV secondary. With a 117V primary, 120VAC into it that won't raise it much. Hmmm???

              Chuck
              "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

              • #8
                I am getting 7.3V and 5.7V on the two other two windings.
                Wall voltage is 121V, transformer is four or five doors down.

                I'm going to give it a try, drop in the 5H Choke, and use a 5K 2W resistor, starting out at worst case, and working down from there, I'm shooting for 330V without load (tubes)

                Hopefully tomorrow, I have more headway than today... Twins with projects, and not an ounce of concentration (for the projects that is) between them.

                Comment

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