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How does this PS really work?

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  • How does this PS really work?

    Hello,

    A thing struck me: How does this power supply really work? It must be the resistors and the current drawn by the attached units that defines the different voltages, or what?

    regards//lasse

    Click image for larger version

Name:	Power- supply board Citation 11.JPG
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Size:	101.3 KB
ID:	1377754
    Perry Mason talking to his dentist:

    "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

  • #2
    Originally posted by lasse View Post
    Hello,

    A thing struck me: How does this power supply really work? It must be the resistors and the current drawn by the attached units that defines the different voltages, or what?

    regards//lasse

    Click image for larger version

Name:	Power- supply board Citation 11.JPG
Views:	1
Size:	101.3 KB
ID:	1377754
    Those, and/or Zener diodes on the main board.
    Francis

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    • #3
      Half wave rectified with no regulation and voltage dividers for drops to target voltages... Not very well I'd imagine, lots of ripple and what not.

      I think you're spot on though. Those 30V outputs must have current draw that pulls the 50V down some more. 15k in series is pretty big, it won't take much current to lose 20V.
      Electronics engineer, woofer enthusiast, and musician.
      Wogg Music

      Comment


      • #4
        Is this working because the system supplied with power is a preamp with a fairly constant current demand from the different parts?
        Perry Mason talking to his dentist:

        "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

        Comment


        • #5
          Originally posted by lasse View Post
          Is this working because the system supplied with power is a preamp with a fairly constant current demand from the different parts?
          That helps, of course. As I said, unless the design is impossibly cheap it probably also has Zener regulators somewhere.
          Francis

          Comment


          • #6
            It's actually full wave CT rectified, I was incorrect above. Also, looking at how they cascade the 2 series resistors with filter capacitance between them probable does a really good job killing the ripple. Pre-amps do have fairly constant current draws too. I'll bet they skipped the zeners entirely for low $.
            Electronics engineer, woofer enthusiast, and musician.
            Wogg Music

            Comment


            • #7
              Originally posted by wogg View Post
              It's actually full wave CT rectified, I was incorrect above. Also, looking at how they cascade the 2 series resistors with filter capacitance between them probable does a really good job killing the ripple. Pre-amps do have fairly constant current draws too. I'll bet they skipped the zeners entirely for low $.
              But this being from a H/K Citation 11, that didn’t stop them from charging $$$
              Perry Mason talking to his dentist:

              "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

              Comment


              • #8
                Originally posted by wogg View Post
                It's actually full wave CT rectified, I was incorrect above. Also, looking at how they cascade the 2 series resistors with filter capacitance between them probable does a really good job killing the ripple. Pre-amps do have fairly constant current draws too. I'll bet they skipped the zeners entirely for low $.
                I'd be afraid of what happens with line variations and time; but yeah, maybe they skipped the 5 cent zeners
                Francis

                Comment


                • #9
                  Perhaps, it’s a good Idea to open the unit and check the voltages? It is a fairly old but recapped piece of machinery, abt 45 years in service
                  Perry Mason talking to his dentist:

                  "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                  Comment


                  • #10
                    Originally posted by wogg View Post
                    Half wave rectified with no regulation and voltage dividers for drops to target voltages... Not very well I'd imagine, lots of ripple and what not.

                    I think you're spot on though. Those 30V outputs must have current draw that pulls the 50V down some more. 15k in series is pretty big, it won't take much current to lose 20V.
                    It's actually full wave rectified. Yes, there is no regulation, but most curcuits, especially tube circuits, are pretty insensitive to +/- 10% B+ variations. At my house I never see more than +/- 5%. The RCRC filters are common in that era equipment and provide very low ripple, but at the expense of heat generated. It is certainly old school and not how a designer would do it today but I wouldn't write it off as being bad.
                    Craig

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                    • #11
                      The interesting part is where (-) is referenced.
                      Guess xmax's age.

                      My guess: 15. His grammar is passable. His trolling is good.

                      Comment


                      • #12
                        Originally posted by PWR RYD View Post
                        It's actually full wave rectified. Yes, there is no regulation, but most curcuits, especially tube circuits, are pretty insensitive to +/- 10% B+ variations. At my house I never see more than +/- 5%. The RCRC filters are common in that era equipment and provide very low ripple, but at the expense of heat generated. It is certainly old school and not how a designer would do it today but I wouldn't write it off as being bad.
                        Corrected that later
                        Electronics engineer, woofer enthusiast, and musician.
                        Wogg Music

                        Comment


                        • #13
                          Zeners have a low impedance but also a lot of noise. There may even be less broadband noise with 2 stage RC filtering that zener regulation at the load. It is pretty standard to use an RC filter after a zener voltage reference to filter the zeners noise.

                          Comment


                          • #14
                            Originally posted by xmax View Post
                            The interesting part is where (-) is referenced.
                            Interesting how? That is how full wave center tapped transformer circuits work. If you mean the schematic doesn't show a ground connection at each (-) point that's fairly normal schematic practice as it is implied.
                            Craig

                            Comment


                            • #15
                              At a glance it's bizarre and a shady ground path especially with unbalanced audio.
                              Although unbalanced could benefit from a floated center tap "ground" I suppose.
                              Fun stuff.
                              Guess xmax's age.

                              My guess: 15. His grammar is passable. His trolling is good.

                              Comment

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