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  1. #1
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    Possible solutions for burnt-out circuitry on Dell Latitude D505 mobo?

    Recently my Dell Latitude D505 quit powering off of the AC adaptor or charging the battery while plugged in. It still runs fine on battery. I've ruled out an AC adaptor problem, and an in-depth (read: take laptop to pieces) examination seemed to indicate that there was nothing wrong with the AC adaptor-to-motherboard connection. Best guess is at this point that a power surge knocked out some of the circuitry on the mobo (there was a storm on the night the problem started, and the laptop was plugged in), a problem that would cost around $500 to fix with a Dell-supplied part. Therefore I am looking at other ways that I could continue to use this laptop.

    Most probably I considered getting several laptop batteries + an external battery charger. Does anyone know of a good place to get an external battery charger?

    Secondly, does anyone know if it might be possible to somehow hack a solution so that I could power the laptop with AC through the battery power connections, which seem to bypass the affected circuitry. Has anyone ever done this before? People on this board have discussed over-hauling laptop batteries using replacement cells, couldn't theoretically someone simply power the connectors in the battery with the equivalent current? I'm really a newbe at these hardware issues, so help would be appreciated.

  2. #2
    Ultimate Member elroy's Avatar
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    Proceed at your own risk !!!
    If the AC power supply puts out the same voltage as the batteries I would solder the wires from the AC adapter to the battery terminals inside the lappy. Then you would have a permanently attached power supply.
    If you want to go with the mulitple batteries and an external charger I would look on Ebay for a charger.
    “Those who desire to give up freedom in order to gain security will not have, nor do they deserve, either one.”
    Benjamin Franklin

  3. #3
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    AC power via Battery connector

    Hi, I opened the battery and took out the cells. soldered the wire from a 12V AC adapter directly to the battery connecter. Then put the empty battery (only has the connecter/circuit board and the ac wires) back to the laptop. Mulitmeter reads 12.58v that is similar to the battery's reading 12.0v. However, the laptop does not turn on at all. Does anyone knows what's the problem/



    Quote Originally Posted by logand View Post
    Recently my Dell Latitude D505 quit powering off of the AC adaptor or charging the battery while plugged in. It still runs fine on battery. I've ruled out an AC adaptor problem, and an in-depth (read: take laptop to pieces) examination seemed to indicate that there was nothing wrong with the AC adaptor-to-motherboard connection. Best guess is at this point that a power surge knocked out some of the circuitry on the mobo (there was a storm on the night the problem started, and the laptop was plugged in), a problem that would cost around $500 to fix with a Dell-supplied part. Therefore I am looking at other ways that I could continue to use this laptop.

    Most probably I considered getting several laptop batteries + an external battery charger. Does anyone know of a good place to get an external battery charger?

    Secondly, does anyone know if it might be possible to somehow hack a solution so that I could power the laptop with AC through the battery power connections, which seem to bypass the affected circuitry. Has anyone ever done this before? People on this board have discussed over-hauling laptop batteries using replacement cells, couldn't theoretically someone simply power the connectors in the battery with the equivalent current? I'm really a newbe at these hardware issues, so help would be appreciated.

  4. #4
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    AC power via Battery connector (Dell C600)

    Quote Originally Posted by d505 View Post
    Hi, I opened the battery and took out the cells. soldered the wire from a 12V AC adapter directly to the battery connecter. Then put the empty battery (only has the connecter/circuit board and the ac wires) back to the laptop. Mulitmeter reads 12.58v that is similar to the battery's reading 12.0v. However, the laptop does not turn on at all. Does anyone knows what's the problem/
    I was thinking about trying the same thing. Does anyone know if a AC/DC to battery terminal approach is possible. It sounds like a fairly sensible fix. I just don't know if the voltage will be the same. Any thoughts?

    -James

  5. #5
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    Yup, I got the same problem. Tried to connect a DC supply from the battery connectors but it didn't work. The pc I'm using just blinked for a second and shut off.

    Some info I gathered from other forums (EeeUser ASUS Eee PC Forum / Running EEE w/ a power supply connected to the battery terminals.)
    suggests that the laptop "reads" data from the batteries and determines their states and shuts off when the requiered response (from the batteries) does not come. Still thinking of ways to overcome this ...else got a brick that won't charge the battery and won't work on AC.

    Somebody else have anymore ideas?

  6. #6
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    Yup, I got the same problem. Tried to connect a DC supply from the battery connectors but it didn't work. The pc I'm using just blinked for a second and shut off.

    Some info I gathered from other forums (EeeUser ASUS Eee PC Forum / Running EEE w/ a power supply connected to the battery terminals.)
    suggests that the laptop "reads" data from the batteries and determines their states and shuts off when the requiered response (from the batteries) does not come. Still thinking of ways to overcome this ...else got a brick that won't charge the battery and won't work on AC.

    Somebody else have anymore ideas?

  7. #7
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    Quote Originally Posted by Nuser View Post
    Yup, I got the same problem. Tried to connect a DC supply from the battery connectors but it didn't work. The pc I'm using just blinked for a second and shut off.

    Some info I gathered from other forums (EeeUser ASUS Eee PC Forum / Running EEE w/ a power supply connected to the battery terminals.)
    suggests that the laptop "reads" data from the batteries and determines their states and shuts off when the requiered response (from the batteries) does not come. Still thinking of ways to overcome this ...else got a brick that won't charge the battery and won't work on AC.

    Somebody else have anymore ideas?
    Just repaired a laptop with the same symptoms:
    Won't charge the battery, won't power from AC.
    Also if you power the AC adapter when not connected to laptop you get green power LED on the adapter. When you plug it in the laptop the green power LED immediately goes out.

    Opened it up and found SO-8 P-ch mosfet by the DC input socket. Source (pins1,2,3) is connected to the inner barrel (+19.5V), Gate 4 gets driven low, applying the input to the Drain. (pins 5,6,7,8) On my board the drain was short to GND. Applying power directly to the Drain via a current limited bench PSU (set 1A limit) showed a couple of volts.

    Placing a finger on the opposite side of the board revealed a SMT ceramic cap getting hot.
    CP13 I think. Opposite side to the power connector, almost under it. I would guess at 1206 or slightly larger and there is an 0402 cap just next to its bottom pad at 90 degrees to it. Cap was glued before soldering so had to flow both sides at the same time with a soldering iron and force off. Would likely have been 1uF or bigger 25V. Removal restored operation. Runs OK without but would suggest putting something in there 0.1uF 1206 50V, perhaps a couple stacked ?

    BTW you have to strip down everything and remove the main board to get to the cap :-(

    Hope this info is of use to someone....

    (EDIT) correction: cap is PC13. Pic showing location of failed cap - D505fix

    Robin
    die4laser.com
    Last edited by brimar; January 8th, 2009 at 07:05 PM.

  8. #8
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    Hi,

    Was the laptop that you repaired also a dell latitude?
    Because I don’t understand which component you removed . So if it was the same laptop type, maybe I can post some pictures of the circuit board and than you can indicate which component you removed?

    Thx
    Last edited by Bomans; December 2nd, 2008 at 06:43 PM.

  9. #9
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    Yes, it was a D505.


    To get at the capacitor you have to follow the full teardown given on the Dell website as service info for the D505.
    Documentation

    If you can send me a photo of the underside of the board in the area of the power connector I might be able to point out the one I had fail.
    There is some metalwork which obscures the underside of the power connector. I ended up hacking this away with a pair of side cutters whilst trying to trace through the input circuit. I think when I found the cap I realised that I could have got away without doing the hacking. Try a couple of photos from different angles so if the cap was just under the metalwork I could still see it.

    The cap is a fairly large ceramic - on the underside of the board and on its own with the exception of a MUCH smaller ceramic one by one of its pads but the smaller one is rotated 90 degrees to it.
    I think all the other large ceramic capacitors in this area are grouped together.

    You might be able to see some signs of damage to the cap.
    when these fail they can crack. The cracks appear as a lighter cream line in the ceramic body of the cap.
    Last edited by brimar; December 30th, 2008 at 08:47 AM.

  10. #10
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    Lightbulb

    brimar,

    I also have the same issue - my D505 works off battery but battery won't charge, and if you plug in the PS the light on the brick goes out. I have my mobo in front of me and see the mosfet you're talking about (PQ12 is silkscreened next to it).

    Not sure where the ceramic cap might be on the underside. You mention CP13, but all the power-related components on my mobo appear to have a P before the component type (PC, PQ, PR, PD, etc.) I found a PC13 in line with the PV3 flexible contact on the underside next to where the power connector is mounted. Hard to tell from visual inspection if it's bad.

    I suppose it could be any of the caps in the power circuit, though...

    How did you connect your low-output PS at your test-bench, and could the resistance test setting of a multitester work as a low-output PS for the purpose of heating up the defective cap?

    (edit) Never mind - I found that cap has a dead short across it using my multimeter's continuity test. Replaced it with one the exact size & shape I snagged from a bad Inspiron 5100 mobo... I'll post back with the results.

    (edit) That did the trick! You're a genius! This little "secret" has GOT to be shouted from the rooftops.

    That just goes to show you that a dead component doesn't have to have any visible signs of damage.
    Last edited by ShineOn; January 9th, 2009 at 12:45 AM.

  11. #11
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    Hi ShineOn,

    Glad to help.
    Just talked another chap through checking this cap.
    His had failed too. Looks like a fairly common problem...
    He took some pics of the board and I marked one up to show the cap position.
    You are right the cap ID should have been PC13.
    I have uploaded the PIC here:
    D505fix

    Regards,
    Robin

  12. #12
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    Smile Fixed a Brick!

    Thanks to all who have posted on this thread. Just fixed a neighbors D505 with this exact problem. You were NOT lying when you mentioned having to break it down completely!
    I just ended up removing the cap entirely. We will just have to see how long it will survive without one.

  13. #13
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    Hi Brimar and thanx again from here. Your help greatly appreciated. My friend's was showing exactly the same symptoms so I followed your instructions and removed the PC13 cap. After the rebuild the power supply shows the green light after plugging in but still nothing from the machine itself. No reaction at all from the power button, lights, beeps, nada...... Do you have any thoughts on where to go from here?

    Thanx in anticipation.

  14. #14
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    Hi,

    If the PSU light kept going out when you plugged it in and now it does not then it looks like you have cleared the short circuit of PC13.
    This capacitor failing would not take out any components downstream of the MOSFET.
    The MOSFET itself should be protected by the overcurrent shutdown of the Dell DC PSU.
    If used with a different PSU there is a chance of damage to the MOSFET.

    I would proceed as follows:

    1) Check the area around the capacitor for solder splashes when you removed the cap.
    2) Check the seating of the connector on the PCB with the power button on it.

    3) Check for incoming power on pins 1,2 or 3 of MOSFET PQ12 (use any connector shell as GND for DVM)

  15. #15
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    oh dear.....

    Thanx for reply Brimar - confess, solder splashes unlikely as I rather clumsily ripped the caapacitor out with a pair of pliers...... Its the dentist in me hehe! Don't know whether to be bothered stripping the whole thing down again if we're going to be down to hunting at component level. You are obviously much more expert than I at that.
    If you're wondering why I posted the question then to explain, I would have been happy to partial strip to check for an unseated processor or something like that.......

  16. #16
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    Ouch. No novocaine or anything?

    You may have damaged the surrounding circuit paths by using a brute-force method. Surface-mount components generally are attached to a thin metal-film circuit pathway with small exposed solder-points on the surface layer of the PCB. If you don't de-solder the component at those solder-points you are likely to damage that delicate pathway and possibly others.

  17. #17
    Thaumaturge Member howste's Avatar
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    Anyone have experience with similar symptoms on a Compaq Presario C300 (C303NR)?

    If I could find a magic capacitor to remove and solve my daughter's problem, I'd be a hero.

  18. #18
    Thaumaturge Member howste's Avatar
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    I'm still pondering on this one. If the problem is the same, am I looking for a short across a capacitor?

  19. #19
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    Hmmm

    Who knows? I wasn't......

  20. #20
    Thaumaturge Member howste's Avatar
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    In the attached photo, the indicated capacitor has no resistance across it. Do I dare to remove it?

    Possible solutions for burnt-out circuitry on Dell Latitude D505 mobo?-hp303-capacitor.jpg

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