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Pyramid power supply regulating poorly

Discussion in 'Electronic Basics' started by Dan, Jun 9, 2004.

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  1. Dan

    Dan Guest

    I've had a 13.8 V, 12 A Pyramid power supply for several years that
    I've used with a battery charger to charge flight packs for my RC
    aircraft. Part of the operation of the charger is to charge at a
    given current for one minute and then drop the current to 0 A to take
    a voltage reading on the pack. In the last year, the power supply has
    started to shoot the voltage up to > 15 V temporarily when the charger
    performs this action. The regulating circuit in the supply seems not
    to be able to handle the sudden load change. The charger, which is
    designed to operate with a 10-15 V source, gives an error message
    regarding the input voltage and ceases to operate.

    My first attempt at a fix was to have a constant load on the supply
    with a power resistor across it's terminals. These became to warm,
    however, and given where I charge (carpet), I don't want to use them.
    Is there a simple fix to this? Maybe a capacitor across the supply
    terminals to soften the sudden voltage change?

    My typical charging currents would draw 2-6 A from the supply.

    Thanks,
    Dan
     
  2. John Fields

    John Fields Guest

     
  3. Daniel Nash

    Daniel Nash Guest

    Well, as far as a warranty, it was only good for a year. I've had this
    supply for about 4. It is only a ~$35 supply, so just looking for a simple
    fix.

    ~Dan
     
  4. Rich Grise

    Rich Grise Guest

    For $35.00, it's only worth repairing as a training project, if you want.

    The thing is broken. Do Not try any work-arounds, you'll just break
    something
    else. Spring the $35.00 for a new supply.

    Have Fun!
    Rich
     
  5. I'm not so sure its your supply. Maybe your charger is getting more
    sensitive to this over time? I'm guessing your supply isn't regulated,
    and maybe its always done this?

    You could get a 14V 1/2W zener diode, and put it across the supply. If
    it spikes, the zener will keep it from getting higher than 14V. It
    should not put much current across the zener. If it does, and the
    zener smokes, I'd get a new supply, or open it up and try to replace
    whatever regulator part is in it.

    For zeners, try one of these:

    http://www.mouser.com/index.cfm?&ha...4V&Dk=1&D=*zener*+*diode*+*14V*&N=0&crc=false

    You can also probably get these at RS.

    Regards,
    Bob Monsen
     
  6. John Fields

    John Fields Guest

    ---
    My point wasn't that you should exercise a warranty, it was that the
    manufacturer would more likely have the information you needed to fix
    it (schematics, troubleshooting advice, etc. or maybe, even, a
    pay-for-repair option...) than we would. A simple email or a phone
    call would probably get you what you needed. Plus, there are the
    repair newsgroups, which would more likely be able to help you better
    than we could.

    BTW, please don't top post.
     
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