Ideas for laptop power supply

Discussion in 'The Projects Forum' started by SuperMoist, Nov 28, 2010.

  1. SuperMoist

    Thread Starter New Member

    Nov 28, 2010
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    hey everyone, I need to fashion my own power supply for my laptop. It requires 15 volts DC at 5.0 amps. I have the old charger but it shorted out and blew what I believe to be 3 resistors off of the board and I can't figure out what resistance they were or even if they were resistors. I'm guessing they were because on the board they were labeled R04, R05, R06. I don't have the money to buy a new charger but I need my laptop asap. I have plenty of electronics and various AC to DC converters to take things off of or reduce, raise or combine voltages. I have diodes, capacitors, resistors galore. Anyone have any ideas where i should start? Old desktop power supply? I'm thinking of redesigning the supply from everything on it only taking the resistors off of something else and making it all onto a new board.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    I'm working on a similar project for an Asus netbook. Mine is 9.5VDC at 2.9A.

    I see plenty of laptop power supplies available online, I suspect that is your best option.
     
  3. SuperMoist

    Thread Starter New Member

    Nov 28, 2010
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    like i said... i currently don't have the money to purchase a new charger and i need the laptop at the latest by tomorrow for work.
     
  4. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Something caused those resistors to ignite. Replacing them will probably just cause it to happen again. Ask Santa for a replacement charger.
     
  5. SuperMoist

    Thread Starter New Member

    Nov 28, 2010
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    yeah my real smart roommate caused them to. The rest of the charger seems fine. He was messing around with the LED on it and left some extra solder on it causing a short but I checked everything else with my ohm meter according to the ratings and like I said... everything seems ok. I don't mind experimenting with it I just need some ideas... if not to fix it then just to fashion my own. Even hardwiring to the battery terminals. I need this laptop running by tomorrow at the latest.
     
  6. iONic

    AAC Fanatic!

    Nov 16, 2007
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    It's good that there is a explainable reason for the damage, but know what the parts are and their values are not a task that will happen overnight. Building a safe replacement is also not something that would likely happen overnight. You best solution would be to borrow an adapter from someone with compatable voltage and a current rating of at lease 4A. You may also need to insure that the output connector is the same and that you match the polarity of the connector(center positive or center negative).

    Easier still would be to borrow the money and buy a replacement! It would be tough to locate a transformer or wall wart that will produce 4 or more Amps after regulating.

    iONic
     
  7. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Why would your friend want to hack around with your laptops supply LED? Get him to buy you a new supply.
     
  8. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    You may also have problems if the laptop is one that checks the power supply for its ID tag. Some power supplies have a small EEprom with a ID on it. If the laptop doesn't detect the right ID it won't power on. If this is the case a direct replacement will be required if you can't fix it.
     
  9. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Yes, Dells have that ID tag system.
     
  10. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Interesting feature...almost an invasion of privacy of sorts...it keep the replacement dollars in Dell's pocket.
     
  11. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    And the Apple MacBooks Magsafe is also proprietary.
     
  12. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    ID tags ..in laptop adapters..noway..

    This is getting too much
     
  13. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Does it mean no one else can make tht?
     
  14. tom66

    Senior Member

    May 9, 2009
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    It's completely stupid as well. That long lead going to the laptop and connected to the EEPROM/whatever - guess what that's called? An antenna. This means it is very susceptible to static damage. I've had two die on me so far, replaced by Dell under warranty. Somehow I think it must cost them more to replace them than the revenue lost to competitor power supplies. The laptop will run off the power supply if it doesn't authenticate, but it won't charge (deliberately disabled.)

    To the OP, designing a switch mode power supply is very difficult. Especially one operated off the mains. There are many safety regulations. You can make a career out of it. To that end I recommend you buy one of these: http://www.maplin.co.uk/Module.aspx?ModuleNo=225874. I don't know where you are, but look for something similar. Then send the bill to your friend.
     
  15. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    @tom66

    u said it won't charge....how is tht possible?

    Does HP use ID tags too?
     
  16. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Apparently his roommate decided the LED needed more solder.
     
  17. freetek

    New Member

    Aug 10, 2005
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  18. SgtWookie

    Expert

    Jul 17, 2007
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    Hey Bill,
    Those SMT UC2842 switching regulators that I sent to you would work fine, with proper aux components. One of the "line item 44" toroids (see the packing list) would be good for a basis of winding a transformer. If you need details on xformer winding with those toroids, PM me. I thought I'd sent you some IRF730's, but I see now that I didn't - they'll be in the next box if you'd like.

    None of this will be fast enough for our OP.

    I would insist that he replace it immediately, as you need your laptop, and the power supply was working just fine until he messed with it.
     
  19. tom66

    Senior Member

    May 9, 2009
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    It won't charge the battery but it will let the laptop run off the AC adapter.

    I don't know about HP. I make a habit of avoiding HP computers, I've had a bad experience with them.
     
  20. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    He broke it, he should replace it. Unless you gave him permission to take apart a perfectly good/needed power supply.

    You can get older notebook power supplies at the no-name-brand PC Stores that pop up in every town, one of them should be what you need. The one here even sells new Branded ones from various manufacturers, as well as spare batteries for a ton of notebook models.
     
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