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Re: [nslu2-linux] Anyone know how the slug 5V to 3.3V power conversion works?

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  • michael taylor
    ... Where are you measuring that power rail? What is the wall-wart power supply voltage unloaded (not plugged into the board) and loaded (plugged into the
    Message 1 of 9 , Nov 1, 2007
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      On 11/1/07, Rod Whitby <rod@...> wrote:
      > I have a slug which is not working (symptom is a short blink on the
      > power led on power-up, and then nothing on any leds after that, and
      > nothing on the serial console), and I'm measuring less than 1V on the
      > 3.3V power rail.

      Where are you measuring that power rail?

      What is the wall-wart power supply voltage unloaded (not plugged into
      the board) and loaded (plugged into the board, measure from the power
      plug on board is easiest)?

      Some quick measurements I just did.

      Wall wart,
      unloaded: 5.12 V
      loaded: 5.08 V

      C45: 5.08V (near RAM)
      C21: 3.3V (near Realtek Ethernet chip)
      C146: 3.xx V (underside, near power switch)
      D13: 3.0V (anode) 2.4 (or 2.5)V (cathode) (underside near 4 LEDs and
      Real-Time-Clock)


      > Does anyone have any details on the slug's internal power conversion
      > circuitry? I'd like to work out what has failed ...

      I assume you have identified U16 as the power management IC, Feeling
      Technology's FP5452
      with under-voltage lock out, and short circuit protection.

      FP5452 datasheet <http://www.dianyuan.com/bbs/u/46/1160442105.pdf>

      Don't know if that helps at all.
    • MIKi
      Perhaps this values should be OK, but as You see w/o more information nobody can say anything about your voltages ... : (
      Message 2 of 9 , Nov 2, 2007
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        Perhaps this values should be OK, but as You see w/o more information
        nobody can say anything about your voltages ... : (
      • Phil Endecott
        ... Hi Rod, I know exactly how it works. Do you have access to an oscilloscope? Phil. (If you cc: me in your reply, I ll see it sooner; I m subscribed to the
        Message 3 of 9 , Nov 2, 2007
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          Rod Whitby wrote:
          > I have a slug which is not working (symptom is a short blink on the
          > power led on power-up, and then nothing on any leds after that, and
          > nothing on the serial console), and I'm measuring less than 1V on the
          > 3.3V power rail.
          >
          > Does anyone have any details on the slug's internal power conversion
          > circuitry? I'd like to work out what has failed ...


          Hi Rod,

          I know exactly how it works. Do you have access to an oscilloscope?


          Phil.

          (If you cc: me in your reply, I'll see it sooner; I'm subscribed to the digest.)
        • sdm485
          The FP5452 datasheet has an application note that should provide the basic design. I just took a look at one of my units and capacitor C45 is bulging in the
          Message 4 of 9 , Nov 2, 2007
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            The FP5452 datasheet has an application note that should provide the
            basic design. I just took a look at one of my units and capacitor C45
            is bulging in the same way as ones on a few failed motherboards I
            fixed a while ago. It is possible that you have the same problem.
            There was quite a scandal about it a few years back. If it turns out
            to be a problem, you need a low ESR device in that location and
            replacing C48 as well would be a good idea.

            Steve



            --- In nslu2-linux@yahoogroups.com, Rod Whitby <rod@...> wrote:
            >
            > I have a slug which is not working (symptom is a short blink on the
            > power led on power-up, and then nothing on any leds after that, and
            > nothing on the serial console), and I'm measuring less than 1V on the
            > 3.3V power rail.
            >
            > Does anyone have any details on the slug's internal power conversion
            > circuitry? I'd like to work out what has failed ...
            >
            > -- Rod
            >
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