Laptop PS has voltage but fails under load

Discussion in 'The Projects Forum' started by cpqfe29, Aug 22, 2012.

  1. cpqfe29

    Thread Starter New Member

    Jan 30, 2010
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    A new co-worker was about to replace a system board in a laptop when it would not power on. He checked the voltage from the brick and it was at 19.5 volts (as it should be). I told him to remove extras (battery, drives, etc). He brought it to my area so I can show him how to take apart a clip and the laptop worked. Went to his desk and nothing.

    It appears that the brick was no longer suppling the needed voltage or amperage when under a load. I've seen it before, but not very common.

    MY question:

    I would like to build some simple load testers. I searched the forum and have an idea of what to do and have seen some interesting projects.

    Adapters: 19.5v 65watt and 19.5v 90watt ratings are what I use most.

    Just to use the 19.5v 90 watt adapter as the main example what are some choices?

    19.5v / 90 watts / = 4.61538 amp / = 4.222 ohms.

    Simple power resistors? what values do you suggest to be safe?

    More elaborate setup to cover a range (65 - 120 watts)? Pots, meter hookups?

    This would not be constant but just a quick and dirty tester to check for operation when in the field.
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Light bulbs are a lot cheaper than power resistors, and they give visual feedback. I think with a little experimentation, you could find the right bulb to give an easy check for a working versus non-working brick.

    But, don't some bricks require data communication with the laptop?
     
  3. tracecom

    AAC Fanatic!

    Apr 16, 2010
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  4. #12

    Expert

    Nov 30, 2010
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  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
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  6. #12

    Expert

    Nov 30, 2010
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    Best one yet by tracecom. 100 watt limit means you should restrict your test time to only a few seconds.
     
  7. wayneh

    Expert

    Sep 9, 2010
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    My approach is still 5X cheaper. For example.
     
  8. #12

    Expert

    Nov 30, 2010
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    A 24 volt car headlight? I didn't know there were 24 volt cars.

    I learn something almost every day on this site.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Ha ha, I learned it only minutes earlier myself. I was thinking two 12v bulbs in series but figured, why not first see what google can find at 24V. Voila. I was amazed it even goes to 100W. :D
     
  10. cpqfe29

    Thread Starter New Member

    Jan 30, 2010
    26
    1
    You are correct sir. Some 'smart' power adapter plugs have three wires. Although the jack looks like a standard two wire plug. There is the outer shell (usually ground), inside shell (usually Voltage), and the center pin - (usually has the same voltage) if tested with a meter will be for communication(controls/limit power I believe based on need). Not all may be the same.

    I believe that you can put a small resistor between the last two pins if you had to use a non-smart adapter (or fixed voltage source) for a temporary fix.
     
  11. cpqfe29

    Thread Starter New Member

    Jan 30, 2010
    26
    1
    I will try some of these suggestions.

    I do have a fix, I just ordered a few extra supplies, but where is the fun and learning in that. :D

    I am keeping the bad supply to compare it with one of the new ones against some of these suggestions.

    After I order some parts I will post my findings.
     
    spark8217 likes this.
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