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  1. #1
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    Scanner power supply bad?

    My old Microtek ScanMaker s400 failed to turn on today, and when I used my digital voltmeter to check the voltage output of the wall-wart under no load, it showed 0.32 VDC instead of the rated 15 VDC @ 1.5A. My question is, Is that a valid way to decide if the wall-wart has died? Or is it possible that it could produce adequate voltage and amps when loaded, but essentially no volts when unloaded? The latter seems unlikely, but my electronics education was pre-IC, and I am in unfamiliar territory here.

    Obviously, I'd rather buy a new power cord/wall-wart than a whole new scanner, if possible.

    Any ideas?

  2. #2
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    It does sound like the power supply has died. You might have to go here to see if a replacement is available:
    http://microtekusa.com/service.php?Type=support
    However, a Search does find sites offering it:
    https://duckduckgo.com/?q=power+supp...00&ia=products

  3. #3
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    Power supplies should produce at least the specified voltage with no load. Anything less than that and it has gone to silicon heaven.

    You can replace it with almost any generic 15VDC, 1.5 A PS, just make sure the power plug is the correct polarity before turning it on.

    cheers, Paul

  4. #4
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    yup, buy a new one 15VDC (must be same), same polarity. Otherwise amps and watts need to be the same or greater.

    polarity symbol that will be on the label, sometimes hard to make out if embedded in plastic housing:
    http://en.wikipedia.org/wiki/File:AC...r_polarity.png
    Last edited by Fascist Nation; 2015-12-31 at 18:00.

  5. #5
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    Quote Originally Posted by Paul T View Post
    Power supplies should produce at least the specified voltage with no load. Anything less than that and it has gone to silicon heaven.

    You can replace it with almost any generic 15VDC, 1.5 A PS, just make sure the power plug is the correct polarity before turning it on.

    cheers, Paul
    Wallwarts yes, switching power supplies no. Switching power supplies need to be loaded.
    David

    Just because you don't know where you are going doesn't mean any road will get you there.

  6. #6
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    Switching PS's are loaded internally so they don't go pop on their own, but they often don't guarantee output voltage stability without a load.

    cheers, Paul

  7. #7
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    Maybe things have changed but I have had more than one computer PS that had no voltage as measured by a digital MM. I think the last time I encountered this was when I was using an old one to do some electrolytic rust removal, thought it was bad before I remembered. PS that technique works well!
    David

    Just because you don't know where you are going doesn't mean any road will get you there.

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