Dead Power brick

Discussion in 'The Projects Forum' started by rigeback, Mar 20, 2012.

  1. rigeback

    Thread Starter New Member

    Mar 4, 2012
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    Hi guys new here, Got a problem here with my laptop adapter HP Delta power brick with a flyback, the other day noticed the led had died so opened the box and starting checking the caps voltages etc, the high voltage is present with 480V on the main filter cap but theres nothing on the 19V DC out. All caps seem to be in good condition and solder joints are ok. I think because of current sensor system the PFC is not turning on?
    The cable plug in to the PC has been checked ok, I would prefer to use the PC without a battery since this battery is pritty old and don't hold any charge, what would be a possible mod?
    Since the battery pack quit I started using the PC without the battery and this might have caused an overload although it does point out that after 2 minutes the charger will reactivate!
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Is this happening? The charger might be fine but is just protecting itself from overload. Could your wires be frayed or connector bent, causing a short?

    I recently shopped for a new brick and found many options under $10. So I'm not sure how much time I'd put into this.
     
  3. rigeback

    Thread Starter New Member

    Mar 4, 2012
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    Reckon I should remove the lead the goes to the PC from the board, which I was going to do anyway as I've got another brick but with lower amp!
     
  4. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    480V? Wow!
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    I have no idea how to repair a SMPS and I chuck them and buy a new one.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    rigeback likes this.
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    It looks to have a laminated transformer (bottom left) to generate the low voltage used by the SMPS control circuitry. Check if that is generating low voltage AC then rectified to 18v or so to drive the control circuit.

    Since there is no sign of oscillation of the SMPS that transformer may have failed or there may be an opencircuit part before or after it that has caused there to be no power to the oscillator/control circuit.

    It's common for those transformers to fail as they have an internal heat fuse in the middle of the primary winding and they run in a very hot enclosure.
     
  8. rigeback

    Thread Starter New Member

    Mar 4, 2012
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    Well I just pulled R13 next to the start up cap which should read 0.13 Ohms I get 0,06 Ohms on 200 which is as good shorted, I think, will change out and let ya'all know.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    You need a very good meter to judge a real difference of resistances that small. Be careful. I'd run a known current through it and measure voltage drop. Even a cheap meter will do fine with that.
     
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  10. rigeback

    Thread Starter New Member

    Mar 4, 2012
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    Well I ran 12.90V trough this risistor and it holds at 0.17V so I guess my perseption was wrong!
     
  11. rigeback

    Thread Starter New Member

    Mar 4, 2012
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    I've come to the conclusion that some thing has blown in the laptop MOBO as I tried a quick hook up with another adapter and theres no power lights although the ID cable was left out in this trial, therefore the power brick could have tripped because of this, in saying this though the power brick should reset within 2 minutes showing the led connected or disconnected.
     
  12. rigeback

    Thread Starter New Member

    Mar 4, 2012
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    Got mobo out and all seems normal, main inlet fuse is good. I would like to modify the inlet plug with a standard round type if possible.
     
  13. rigeback

    Thread Starter New Member

    Mar 4, 2012
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    Concerned about the computer just now since I found one of my fans was not working and the mobo will circulate a direct 19V connection, cpu might be fried! I guess I should start a new thread it the problem persists. As for adapter I'm seriously considering ordering a new one.
     
  14. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I don't want to sound mean but at this point i'm starting to think you should get a professional to look at your computer, or just buy a new one (and don't fiddle with its internals). :)
     
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