Thursday, July 8, 2010

Laptop Rebooting- DV6000, F700


While working on a DV6000 today I decided I should also address other problems with these models while working on the DVD production. 


As it seems this problem is also quite common, Rebooting, looping, restarting.  Never getting to the Windows startup screen.


OK there are several causes of this scenario with the ribbon cable being shorted or defective.  The ends of the ribbon cable can lift away from the surface when inserted and shorting the lead from the adjacent wire.  Some times it will short and cause the wire to burn. Other times it will cause the REBOOT/LOOP issue.  


Also verify that the Coin Sized CMOS battery has 2.5v- 3v, if not or voltage is low, all kinds of problems may present themselves.  Correct operating voltage is needed to read the CMOS data, or the data may be corrupt or deleted.


How to test/bypass these?
1: Disconnect the PWR connector cable, and turn the system on with the remote control (if you have one).  Make sure the battery is good in the remote.* 
2: Substitute with another cable.


Other issues presenting same problem
CMOS is bad** - If the CMOS is bad it cannot be read or written to- and the system continues to try to write/read data from it.


The Dual Channel MOSFET - one output is shorted or open. (or both)
When the MOSFET has about 3.25v on pins 1 & 3 it should be considered working. There should also be the same voltage on the Drain side (pins 5-8). This will take the voltage up to the legs on the PWR button and when the button is pressed this voltage drops to ZERO and the unit turns on.  The original part was a AO4812 and sometime has been replaced with a ME4920.


*How can I test the IR remote?
Since most people have a digital camera nowadays the cheapest and easiest way is to press the power button on the remote and look at the camera's LCD display.  You should see the remote blinking.


**How can I test the CMOS to see if it is working correctly
Disconnect AC adapter! 
With the ribbon cable connected to the power button, hold the button for 15 seconds to clear the CMOS. Now hold the PWR button down, and at the same time insert the adapter into the DC JACK.  The lights should come on for about 5 sec. then go off. Release the PWR Button. Now attempt to power on normally. Sometimes this works when the CMOS settings are bad.


Watch the orientation of PIN 1.
On DV6000 the leads are up 
On the DV9000 the leads are down
On the F700 the leads are down.
If your memory/recall is bad- take a picture before starting.


Note:  The black KOTEL ribbon cables are flimsy and the strain-relief/support is too close to the leads to help matters.  Remove and insert less often as possible.  If they break you'll wind up looking all over for a substitute. Though similar pitch and length cable can be found on GATEWAY MA3/7 touchpad. (Techs at shops should have a few of them around)  


Also the Gateway MA3 has two of the AO4812 chips on the back side near the 28 pin power output IC. Incase you were needing one. 

11 comments:

  1. Also need to mention that the DV9000 series is virtually identical, except they have a deeper battery connector, WiFi lights, and Dual SATA connector the boards function and appearance are quite similar.

    Lowest common denominator - during test phase, I use TL50 CPU's rather than some of the TL60 & TL64 AMD chips because the clock speed is slower and is less taxing on the system during troubleshooting. You may not need to do this.

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  2. Hey Mayo, I got a DV9 (9308nr) on my desk with the reboot loop. I have defiantly tracked it down to a CMOS problem.

    The first time I had it open (and thought it was repaired) I got it to boot up, and while turning the board over to get a temp. reading, I touched somewhere on the board and the screen went from "Operating System Not Found" to scrolling "Phoenix Bios Copyright blah blah blah" across the screen. I almost started freaking out I thought I must have shorted something out.

    Well after that (and I am still not sure what I touched to get this to happen) The laptop was working great. I did over 100 hard shutdowns (with the hard drive out of course) without a single problem. Finally today it came back to me, the user said after burning a DVD and then rebooting it started the loop again. A bios reset gets it starting every time.

    Also, FYI the CMOS reset method that you posted does not usually work for corruption of this level. What does work (for any HP) is to:
    A. Unplug, remove battery for 3-5 minutes.
    B. Hold down the Insert/Scroll key on your keyboard.
    C. While holding down the Insert/Scroll key, press and hold the power button for about 15 seconds. (You will see the lights flash and then turn off)
    D. Release the keys and boot normally.

    This is the only method I have had work. My question is, do you have any idea what I may have touched last time that caused this scrolling message and some sort of CMOS hard reset?

    Thanks,

    Mike

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  3. Typically the CMOS reset method does work, but if other problems are present, such as an open cap, shorted cap or shorted resistor it will not. And when you turned the board over (and not finding SATA) it shows that some other problem still exist.

    Essentially your method is a CMOS reset draining the values in the chip and back to default settings by holding the button.

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  4. hi friend do u have schematics from this laptop /?? if u have and u can send me please

    higorsantana@hotmail.com

    thanks

    ReplyDelete
  5. Higor sorry I don't have any information on the models avbove. Just doing it the old fashioned way, tracing paths of electricity and sometimes getting lucky.

    You are lucky when you see what chip is burned, or capacitor is blown or disconnected. Other than that I just have to follow the current.

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    Replies
    1. yeah it is kinda hard to visually tell which ones are bad. time and patience my friend.

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  6. Thanks' for the info about the ribbon cable, it made my dv9000 return from the dead.

    Here are some more hints.

    Other ways to start the dv9000:
    1. Use the normal start button and immediately remove the ribbon cable from the system board. That worked for me and indicated where the problem was.
    2. Remove the ribbon cable from system board and use a docking station connected to the special connector on the left side to start it.

    By using a magnifying glass I could see that one of the leads of the ribbon cable was leaning on its neighbour. There was a need for a separation. I used a small, not to sharp, knife to push the lead aside into its correct position. It seams as the adhesive on the plastic bearer is sticky enough to allow for this repair. Reconnecting the ribbon cable and YES, it worked.

    Then I did not want to disconnect the ribbon cable again so I left it under the top cover. It seems to be enough space to not damage the cable here. Hopefully it will not be damaged over time.

    Now the only remaining problem is that power from battery is not working. Does anyone know what shall be on the pins on the battery connector? When battery is disconnected I only have 3.4 volt on some of the pins.

    ReplyDelete
  7. Lennart:
    You can start the DV9000 with the remote. Also with some sharp scissors cut off about 2mm if the short is near the ends. When cutting , go down the space between the contacts with a toothpick to make sure they are separated.

    The voltage on the pins should be 10.5v to 12v.

    When the AC is connected to the laptop you should get voltage on both sides of the AO4407/27 chip (pins 1-3 and 5-8)when the battery is in. If the battery is out, there will not be any voltage on pins 5-8.

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  8. im in dire need of a part number for an ic chip on mt dv 6000 i blew the 8 pin ic right next to the cmos battery any help is greatly appreciated

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  9. Without an exact board number there is no way to tell the part number. There are over 100 different DV6000 variations.
    And some have coil cell batteries in a clip, others have batteries that are shrink wrapped and plug into the board.

    ReplyDelete
  10. hi mayo, im having some issues testing mosfets. maybe you could help me out?
    i have this same issue on a dv6000, but theres no mosfet between the power ribbon cable and panel jacks. How do you check the mosfets with the single gate(i think is pin 8)? do you set the multimeter to diode(2K)? i have a cheap velleman multimeter. because i couldn't get any voltages from the pins (1-3)(5-8).
    thankx in advance.

    ReplyDelete

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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