Sunday, January 16, 2011

DV7 Dead No Lights, will not charge

DV 7 Power In Section
Getting back to postings. A DV7 was brought in that was totally dead and would not even light the LED on the side power connector. 


These units are totally different than the previous DV2xxx, DV6xxx, DV9xxx series, and the power indicator on the side gets power from the board not the charger. So if the power in is good, it will not give you any indication, because it draws 5v from the laptop and not the DC jack circuit board.


When checking the system I used a meter and checked the red wire (Line In POS+) and it had the 19v and the yellow was 0v. Moving to the next chip in the circuit I tested the SI4835 mosfet and it was dead shorted in both directions. So I took it out of circuit and tested it on the bench with meter- same thing.  The mosfet was shorted. When it should allow current in one direction only, it was allowing in both directions and the unit would never power on. Without having the exact number available, I went to the manufacturers site (Siliconix)and Vishay to check the specs on the chip. This allowed me to use what was available, and not having to go out or wait for a replacement to come in.  In this case it was a AO4407 which I keep on hand. Replacing the chip the unit powered on, and charged the battery properly.


Reminder: The site/blog is to assist TECHNICIANS. I cannot help individuals without any technical training or schooled in electronics because most of the problems covered are not user servicable.

37 comments:

  1. Welcome back, and a belated happy and prosperous 2011! Please keep these blog posts coming. They are *very* helpful.

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  2. Thanks Larry.

    I am still looking for other techs/blogs that are doing the same thing. I would keep us from all having to discover it on our own.

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  3. I now have two of these laptops (DV7) with the same problem you describe but I've checked the SI4835 mosfet (along with every other mosfet on the board(s)) and they test fine. Any other suggestions?

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  4. Mayo:hi can you explain in which blog you r continous avilible

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  5. MattBrad2: the only suggestion I have is to follow the 12v IN. I haven't had to do too many of the DV7 and the design is throughly different than the DV6K/DV9K series. I guess you could say that I fix them as I get them.

    I am trying to cut down on spending too much time on one series. Though the older DV series are in abundance.

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  6. Asifnawaz: I am never continuously available. I have various projects I am doing and hardly get time to come back to the blog. I try to post when I get a chance. And currently my camera is full of pics but not much time to post them in detail as before.

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  7. Just a FYI, all 3 (2 DV7's 1 DV3) had the same problem. The TI 24740 battery management IC was bad. I had checked all mosfets and nothing was shorted. I had a DV6 come into the shop today. I'm interested to see if it has the same problem. I have a feeling this is going to be a similar problem as the older DV* GPU problem.

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  8. Thanks MattBrad2: I have a DV5 that is exhibiting weird symptoms it too could be controlled by the same TI chip. Now thats a heads up I can appreciate.

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  9. Thanks MattBrad2: I have a DV5 that is exhibiting weird symptoms it too could be controlled by the same TI chip. Now thats a heads up I can appreciate.

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  10. Hi mayo
    i have Lenovo w510 which was password protected
    i dissassemble it and found the rf24c08 read it to remove password, but after that i tried to power on the pc and found that nothing is on the screen only the fan works for a while then it is off,
    the heat sink got very hot sooner
    what may be the poblem?
    will it be bios problem
    i smelt nothing strange, and found nothing blown.
    and is there a way to get the bios file in bin format?
    thanks

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  11. phillip: I've since left Thinkpad password methods to those that are better than myself. http://www.allservice.ro if you use Google Chrome it will translate from Romanian to English if you cannot find the English link on the page of which most of the site is since so many countries have English speakers now (via Computer)

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  12. hi mayo hardware i need help i have hp dv7 power on two second power off can you help me thanx for help

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  13. Burim: That problem is usually associated with BIOS. The information cannot be read/sent to the CMOS or vice-versa. It could be something as simple as a dead CMOS battery or even more difficult as bad capacitor/mosfet. It is difficult to diagnose from afar, but most techs can surmise areas to test.

    1: Check CMOS battery for 2.2v to 3v
    2:try different ram or only 1 stick
    3: Try cold reset of CMOS

    Also before doing any repairs, check the power supply, be sure to clean heatsink, and apply new compound.

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  14. Mayo, I got a DV7 (Core i7 and ATi Video card )with a wierd problem. I made a repair on his motherboard...the small capacitor near the card reader was shorted. I putted a new one and the notebook worked fine for 1 week.

    1 Week later he came back to me again telling that the notebook got too hot near the GPU/CPU area and them turned off by it self and now he wont turn on.

    I already checked all the capacitors and mosfets and they all seems to be fine.
    When I plug the power cord, the LED in the power jack lights on and the motherboard charge the battery normaly. But when I press the power button, nothing happens...

    Really strange, because nothing heats, (Just the mosfets when the battery is charging up )...

    I'm wondering if it can be a GPU problem...

    Can you give me some hint?

    Thanks a lot!!!!

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  15. Mayo, I got a DV7 (Core i7 and ATi Video card )with a wierd problem. I made a repair on his motherboard...the small capacitor near the card reader was shorted. I putted a new one and the notebook worked fine for 1 week.

    1 Week later he came back to me again telling that the notebook got too hot near the GPU/CPU area and them turned off by it self and now he wont turn on.

    I already checked all the capacitors and mosfets and they all seems to be fine.
    When I plug the power cord, the LED in the power jack lights on and the motherboard charge the battery normaly. But when I press the power button, nothing happens...

    Really strange, because nothing heats, (Just the mosfets when the battery is charging up )...

    I'm wondering if it can be a GPU problem...

    Can you give me some hint?

    Thanks a lot!!!!

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  16. Alucard/Dracula: The problem could also be the the fan/gpu heatsink. Some times when the compound dries out too quickly, it offers very little protection and cooling. Also that the heat sensor could be defective. I have not experienced that issue. But maybe a clearing of the CMOS (cold reset) could bring it back to life enough to check with SpeedFan to get the sensor readings.

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  17. I just checked the southbridge, it's shorted.
    Thanks for the tips anyway!

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  18. I'm looking for some help in Sacramento, CA. How do I find a real tech in my area to repair my boards? I have 2 dv7 boards - one with an NG vga chip and the second with the power issue. They are both dv7-1245dx. And a couple of other mb's. You don't just look in the yellow pages!

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  19. I feel ya Robt. seems like the schools are pushing out Windows and peripheral installers and no electronics techs. Many boards have a $39 repair, but shops make you buy a new mobo for a lot more, then add labor. That was the reason I started here in CLT. I think you may have to talk to a computer shop in the area, and ask who's good at component level work.

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  20. thank you for taking the time to make this blog, i have this issues, PSU is good, DV7-1025nr does not power on, i am pretty sure this issue is mine as well, do you have another one of those mosfets? can you sell me one? hardwaremack at gmail dot com, i am in detroit michigan.

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  21. Hello Mayo,
    i've been trying to locate a site where i can download the schematic to my dv7 motherboard, the mosfet you pointed out is burnt in my motherboard. Do you know where i can get the schematics for my board. jbk00 la-4091
    hp model # 506124-001
    i want to order the right mosfet the first time.
    thanks
    Cesar

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  22. Hey, just finished with a DV7-1020US that had the power issue. Turns out that the AO4433 (PQ103) chip is shorted in both directions. However, they're out of production, and digikey does not stock any fet at the same specs. Any idea on a replacement? I've tried other fets with similar specs (or as close as I could get), but nothing is working.

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  23. Cesar: I gave up looking for motherboard schematics long ago. I had seen a Vietnamese site years ago with several, but I did not save the link.

    AirFrance: You can find the AO Mosfets at http://www.aosmd.com
    Alpha and Omega has the complete list. If you get the specs for the part, you could cross reference it at Newark Electronics. http://www.newark.com

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  24. Hi there,

    Just a quick question ,

    I have here this laptop , hp pavilion dv7-1240eb, symptoms are,

    works fine on a charged battery,
    when charger is connected , led indicator on the side works
    does not charge the battery, an does not power on with only charger connected .

    You think this could be related to the SI4835 mosfet , or should i look more in the direction of the TI 24740 battery management IC, like mentioned in this thread .

    Advice is always appreciated,

    Regards from Belgium ,

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  25. Dear Belguim (Above) I have the DV7-1240 us with the same requires battery and will not charge. The chip on the under side of the board from the SI 4835 on mine is so badly smoked that i cannot read what chip it is. If you (or anyone else) would tell me what the chip is it might help us both.

    Thanks in advance,
    GlennNDavis at fuse.net

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  26. Glenn: It too is a SI4835.
    Though an AO4407a or AO4427 would work also.

    That chip, when it gets the signal (~3v) from the charge pin on the battery connector, closes the gate so that power is sent to the battery, and charge light comes on.

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  27. Hi Mayo,

    thanks a lot for your solution, I wanna make sure my dv7 is causing the same issue as well, as I do not want to buy the part and replace it just to find out that it still wont work. I am 80% sure that it IS the problem, since i have worked on this laptop 3 times for other issues, but would like to eliminate all doubt before proceeding.

    I have looked around, but cant figure out how to tests the components. I also have 2 mosfets on my board instead of 1. can you give me a quick guide on testing it? i have never done component testing before, so I dont want to risk frying it. he he he

    here's the document I was reading.
    http://www.vishay.com/docs/69953/si4835dd.pdf

    from the first page's diagram I understand how it's positioned, but i dont know where exactly they are, from comparing the drawing to the actual one.

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  28. also, is there a difference between SI4835d and SI4835b mosfet? basically, is it a problem if I use one with a different channel?

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  29. Hi Mayo,

    Given your experience with dv7 power problems, I'm hoping you may be able to save me some time in troubleshooting my particular issue. It's a dv7-1232nr that won't boot up. The symptoms are: power LED does not light when plugged in (but flashes very briefly when plug is disconnected), battery light keeps flashing, lights and fan momentarily come on when power button is pressed but then shuts off momentarily. When I first got the laptop, there was no flashing battery light with the AC power plugged in. The power jack was very loose, so I surmised that this was the culprit given this and reading numerous reports of people having a similar issue that was solved with new jack. I bought a new jack, installed it, and observed the flashing battery light. I figured I had the problem solved, but trying to power it up resulted in the same problem--fairly rapid shut down. I read on-line about a fellow with this issue who tried powering up the laptop and then immediately ejecting the battery. He said he did this about 20 times before the computer finally started up. I tried it with no luck, but did observe one peculiar behavior: a couple of times, the computer shut off immediately, then tried to turn on by itself again only to shut down again (with the battery not installed mind you).

    Now, I have a dv5 laptop that will run without a battery. The power LED will light when plugged in. But this dv7 does not show any sign of power if the battery isn't installed. That leads me to believe there's some kind of power management issue. Perhaps the same one you have documented. What are your thoughts given what I have described? Thanks a lot!

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  30. Cytherian: You have a short in the front end, either the first mosfet on topside by power-in, or on the bottom. It seems to be a dead short.

    Check with meter. Also check ceramic caps in the front end. If you tried a fully charged battery it may run/come on but the short may also keep it off until corrected.

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  31. I have the same situation with a DV7, is there anyway that I can send you the motherboard so you can fix it ?
    How can I contact you ? I'm in NYC.

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  32. Thank you very much for sharing this. Had a DV4 with exact same symptoms, now fixed thanks to this info.

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    Replies
    1. Sure, glad I could be of help. Also thanks for donating. Many don't know but even $3-5 helps me buy parts for other experiments.

      Everything is not so simple.

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    2. Well, it's not easy to donate without creditcard/paypal. Just got paypal especially for this :)

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    3. Thanks Ser - Other videos are coming out. I'm busy with other projects, and lately getting a lot of programming tasks and animation.

      Delete
  33. I have a DV7-1150ev(LA-4082P) that when i connect the power supply and the battery is blinking the charging led ( the side led near the power connector is not light up) and i hear a click noise. When i press the power button is power for 1 sec and shutdown again, Also with the charger only, no light at all and when i press the power button nothing happen. Any help?

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    Replies
    1. It's a MOSFET problem but not in the DC In area, may be over by the charge circuit. Usually shorted. They are the flat type MOSFET's without legs.

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I cannot repair laptops for you via the internet, I can only answer questions related to posts. This is because I have not had experience on every motherboard that is out there. Bear with me.

If you do need it repaired. Contact me for quote (US/CDN Only)

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