Dead notebook power input

Discussion in 'General Electronics Chat' started by Leigh, Jan 8, 2011.

  1. Leigh

    Thread Starter Member

    Feb 11, 2010
    20
    3
    Hi. I have a lovely Hp Pavilion dv6500 notebook computer. It has been rendered useless by some failure in the internal power supply circuitry. It will boot for about 60 seconds, then abruptly switch off. A known good alternative power supply mains pack does the same thing, so it is internal to the machine.

    I have followed an excellent tutorial online, and pulled the notebook to bits, looking for a broken power socket pcb track, cold solder, etc, and also looked for obvious signs of fault, finding none. I cleaned all the cooling fan tunnels, ports etc.

    The system ran fine on it's battery, but with no power input, the battery went flat.

    I would like to at least use the machine in a non-portable application, so would be happy to run it by removing the battery, and hot-wiring the required voltages to the battery input to the computer. Here is my problem. I cannot find details of the pin-outs of that connection. I need to convince the HP that a real battery is connected.

    Any tips, or complete solutions, gratefully received.
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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    Matching the battery voltage on the contact pins is the "standard" way of doing this on cording a cordless device.

    BUT, If I remember correctly, there are often more than 1 output voltages with some laptop batteries.

    SO, If your battery has more than 3 contacts (Positive, Temperature, and Negative) you will want to find a schematic, OR a friend with the same model laptop (or same battery in another laptop).

    Have them measure a properly charged battery at all the contact points and note the voltages.

    This may be a little more difficult than you think, because most laptop batteries contain a microcontroller that talks to the computer about temperature and charge status/remaining power.

    If the laptop does not have proper communications with that chip, it may be a more complicated job.

    It would THEN require you to open the case of the old battery (never a good Idea) and remove the charging circuit.

    Some reverse engineering may be required to "fake out" the laptop and battery circuit into believing it is always talking to a fully charged battery.
     
  3. dBm

    New Member

    Jan 8, 2011
    1
    0
    Hi Leigh,

    First up, have you checked to see if your battery is part of the extended recall?

    http://www.hp.com/support/BatteryReplacement

    Here's a good place to start looking for info: http://h10025.www1.hp.com/ewfrf/wc/...link=ot_we/prodlink/en_us/3380544/loc:0&cc=us

    Here's a link to your service manual: http://h10032.www1.hp.com/ctg/Manual/c01295877.pdf

    A few other thoughts-

    60-seconds sounds about right for failing POST. Try getting into BIOS and disabling the Fast Boot option and the Splash Screen option, if present. This will cause the diagnostic results to print to the screen. [If you are past teen age you might need to recruit a young gamer to do the typing :D ]

    Remove the battery, turn the unit on and use a volt meter to verify that voltage is coming from the recharging circuit.

    Remove the battery, memory and hard drive to see if it will boot as far as the "No operating system" prompt.

    Doesn't seem likely given your description, but consider taking soldering iron in hand and reflow all the connections having to do with the power connector. Sometimes the mechanical movement of plugging/unplugging causes hairline cracks in the solder joints.

    Cheers!
     
  4. Leigh

    Thread Starter Member

    Feb 11, 2010
    20
    3
    Thanks to you both for valuable hints, observations and links. I am sure there is communication between the computer and the battery pack. I will work through the suggestions here that I haven't tried yet. It could take a while. I might also try direct contact with HP to see if they think it is possible.

    I suspect something like building a resistor chain to simulate what the battery pack electronics wants to see, _might_ work, as long as that means it is communicating with the computer happily.

    And whilst I am in my 4th decade of computing, it is possible that a young Gamer could type faster, but also could get into trouble a lot faster than I :p

    So I'll tread carefully.. I don't like smoke! Thanks again.
     
  5. tom66

    Senior Member

    May 9, 2009
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    If you remove the memory, the machine will not boot at all.
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    Actually, it may.. Older machines needed a stick to boot, or it would just sit there and beep a code at you.

    Newer machines have some on-board cache, or other eeprom that will handle all "pre-post" and "bios" operations.

    This will likely be enough to get you to the "No operating system" message.

    It will look funny when your memory check only goes to 640k ;)
     
  7. tom66

    Senior Member

    May 9, 2009
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    I beg to differ. The CPU will not be capable of loading the BIOS image into memory without memory to load it into. ;) You can try it, but I'd be surprised if it works. Anyway, the only way to test is to try.
     
    Last edited: Jan 10, 2011
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    Im not opening up mine until after the warranty expires, so you've got 363 more days to beg and differ ;)

    What I was getting at, was the BIOS may be loaded into CACHE memory rather than extended memory. The cache is part of the chipset, not the add-on memory.

    I would normally agree with you, but when dealing with laptops, battery life is prime, so using the L2 and/or L3 is less expensive, in battery time, then using a 2 gig memory stick.

    I dont know if I am right, im just saying it is likely.
     
  9. tom66

    Senior Member

    May 9, 2009
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    Cache is not directly addressable by the CPU but only by the on-chip memory controller. And cache is almost always on the CPU, rarely off-die, except on some older desktop Pentium processors. That's why laptops only last a day or so in standby, when they could probably last a month or so.
     
    Last edited: Jan 10, 2011
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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    Actually newer laptops dont typically use the expansion slots. I just found out.

    Unlike desktops, laptops are on-board. but also have expansion memory.


    So if you remove all ddr memory "cards" from the laptop, you will still be running with original, non removable memory.

    So the guy was right to suggest removing memory.

    That would help find out if it was additional add-ons that caused the problem.
     
  11. tom66

    Senior Member

    May 9, 2009
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    Maybe it's different from when I last upgraded the memory in my laptop from 512MB to 768MB (that was an old one but the extra 256MB made Ubuntu greased lightning.) There were just two 256MB sticks. It's worth trying anyway.

    Don't forget some video cards may have dedicated memory. In which case this will be usually on the motherboard and not upgradeable.
     
  12. retched

    AAC Fanatic!

    Dec 5, 2009
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    True.

    I would think many of the integrated sound/video/NIC/etc setups would also be a little happier with mobo based memory.

    not as many "what ifs" to deal with when you consider the possibility of all the ram manufacturers that may be stuck in those slots.


    OR, if someone used a 133mgz ram stick and then complained that there 3ghz laptop was not running fast. ;)
     
  13. tom66

    Senior Member

    May 9, 2009
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    NIC and sound usually use DMA. That's not to say they won't have on-chip memory. Video can use main memory or dedicated memory.

    I want to see 133 MGz ram. A mega-gigahertz! ;)
     
  14. retched

    AAC Fanatic!

    Dec 5, 2009
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    HAHHAHAHAHAH!! My bad ;)

    I cant wait for the Mega-Giga-Hertz chips to come out ;)
     
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