# Advanced laptop motherboard troubleshooting - POWER related: HP dv8000



## blombardo (Aug 22, 2010)

*Simple summary:*

I have an HP dv8000 that will only function through battery power. 

I have another (good & working) dv8000 to use for parts testing; and I have determined the problem to be one of the chips on the motherboard.

I'm limited in my ability to test this; I have a not too tiny multimeter... smallest available at radio shack -but its WAY too fat to use for testing such small parts...

Anyone have a suggestion on how I can figure out which chip(s) on my motherboard are bad?


*Basic description of the design:*

18volts + ground comes into the dc power jack - 2 wires carry the current about 4 inches and a plastic connector splits it into 2 18volt wires and 2 ground wires - they attach to the motherboard (where I have all good connections).

*Location where I believe the problem exists:*

I think the ac input has somehow fused with the battery input - and in turn disconnected itself so that the laptop believes that both the battery - and the ac input are BOTH battery. 


*Odd notes:*
1 When a fully charged battery is installed laptop works perfectly

2 When battery is removed – and ac cord plugged in – laptop gives fast blinking lightening bolt (warning that the battery is too weak to be used ) – of course the battery is NOT INSTALLED – so this blink error should not be happening.


*Just to clarify to anyone kind enough to shoot a reply:*

I have a good power adapter.
I have a good battery.
I have the correct voltage reaching the motherboard through the cables.
The laptop seems to think that a weak battery is attached (when NO battery is attached and the ac adaptor is plugged in)



I would like a flow chart for the motherboard to determine what could be faulty so I can repair it... 



There is another post here with some helpful information - though not helpful to me... It is here:

http://www.techsupportforum.com/f108/hp-dv8000-no-video-turns-on-and-power-light-flashes-rapidly-447679.html


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## blombardo (Aug 22, 2010)

Fixya has some info related to this- of course none of that data was helpful to me...


http://www.fixya.com/support/t248259-hp_pavilion_dv8000_help


This info is interesting... but not exactly helpful either.

http://www.uofr.net/~greg/hardware/laptop_power_troubleshooting/


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## night_shift (Sep 8, 2009)

Hi blombardo and welcome

You have researched this very well. You have been busy.



> I have a good power adapter.


You appear to have a good fault finding strategy and a plan, but just for my information, I know you have checked the output voltage and you are probably aware that most chargers and laptop power control circuits use SMART technology to communicate. I was wondering if you have tried another OEM charger to eliminate a communication problem. 



> I think the ac input has somehow fused with the battery input - and in turn disconnected itself so that the laptop believes that both the battery - and the ac input are BOTH battery.


I'm puzzled to why you think there is ac voltage at your battery!

The ac is only present in the charger, all inputs to the laptop are smooth regulated dc. The only place you could (due to a fault) get the ac fusing with any dc component would be a short circuit between the mains stepdown transformer and voltage rectifier in the charger. This would be a catastrophic failure. Has the laptop or charger ever been exposed to liquid or high humidity. 

There is also power protection on your motherboard power control circuit from voltage surge, RF ripple, over/undervoltage, over current and reverse polarity protection.

So faults like this are generally -

1. Power/charger failure.
2. DC jack socket/plug failure.
3. Motherboard power controller failure.
4. Failed or failing battery.
5. Rarely a bios issue, laptops have a fairely basic bios.
6. Cable damage ac mains or dc side.
7. shorts on your power pins or battery connection.
8. One number One issue is due to moisture ingress.

As for fault finding on the motherboard you would need to use an oscilloscope with the design drawings at hand (manufacturers dont part with this) to check voltage levels and ripple induction. You would not even get the manufacturer to do a mobo rapair to component level. 

1. I would prove your charger works 100%.
2. Check for the obvious. Cable damage and shorts etc.
3. Have a good look at the mobo for signs of component damage near or around the power input connector to your motherboard. Capacitors especially the SMD electrolytic capacitors, if these have been stressed they will bulge and leak. Look for burned components or fried tracks.

I like to do obvious and simple thats where most faults occur. You appear to have a good grasp what you want to do. As for drawings and component identification you will be very hard pushed to get this info.

Hope some of this helps.


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## blombardo (Aug 22, 2010)

First to answer questions - 
1: I have tried three known good ac adapters.
2: I do not see any obviously swollen/damaged capacitors or any other damage - 45 minutes worth of looking under a magnifying glass...
3: The reason I commented "ac input has somehow fused with the battery input" is because on this damaged laptop with battery removed and AC plugged in I receive an LED code that is defined to mean 'battery is too low to start the computer' On a GOOD laptop with battery removed and AC plugged in - NO lights should light up - until you press the power button.



More specifically the area where I belive the problem lies would be in one of the resistors near PL15 - I can not replace such a small component by hand... Though I am not certain of this because I lack the knowledge to determine the tolerances of each component on this motherboard; many surface mount parts are not labeled.

There are SIX terminals on the battery; with the battery removed the power throughput on each motherboard battery connection should change.

Battery removed on a good laptop=
1: negative
2: +3.31 volts
3: negative
4: +5.0 volts
5: +5.0 volts
6: +1.44 volts

Battery removed on my DAMAGED laptop=
1: negative
2: +.77 to +.89 constantly changing voltage 
3: negative
4: +1.2 to 1.30 constantly changing voltage
5: +1.15 to 1.30 constantly changing voltage
6: +4 to +7 constantly changing volts

It is obvious to me that with varying power outputs like this - all at such low numbers I can not expect this laptop to start up - So one of the parts between the ac input and where the battery input goes must have gone bad - because with the battery installed the voltages go back to normal; and of course the battery will never charge...

Battery Installed on a good laptop (same readings on my damaged laptop)
1: negative
2: +2.0 volts
3: negative
4: +5.0 volts
5: +5.0 volts
6: +16.0 volts (probably changes slightly depending on the strength of the battery)




I fear that it is a chip capacitor, or chip resistor that is causing my problem and I have no clue how to identify which it could be - or if I could identify it many are too small to replace by hand.

If anyone else has any ideas I'll be happy to pull this out of my closet and take another look at it... Otherwise I'm afraid the generic answer is 'motherboard failed - replace entire motherboard' (suckiest answer in the universe


Does anyone know of a company that is equipped to repair this type of thing (I'm sure 'reasonable cost' doesn't fit into this category... even though the parts I need will cost a fraction of a penny and someone will have a reel of 10,000 sitting on their shelf...)


I have seen this EXACT problem happen numerous times on VARIOUS makes of laptops -- 'Battery not charging' - 'Laptop will only run on battery power' - and I have replaced the entire motherboard time and time again because I have never been able to repair it...


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## blombardo (Aug 22, 2010)

http://h30434.www3.hp.com/t5/Hardwa...-battery-LED/m-p/165589/highlight/true#M19323


Seems I may have found a company that has experience with this exact problem... if only their secrets were revealed to the public so I could avoid paying a $100.00 + fee for a 5 minute repair job...

FloridaMotherboardSpecialists is their name -- I'm researching them now...

http://www.bstardigital.com/floridamobo/index.html


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## night_shift (Sep 8, 2009)

Hi 

After reading the whole post again -



> I think the ac input has somehow fused with the battery input


What you mean is the dc side power cord (dc jack plug) from the ac acadaptor. The dc jack as you know feeds into the power control board/circuit. Some laptops have a separate unplugable board, not sure about yours? If it has it only requires a new board. The description you are giving me leads me to believe its integrated into the mobo. 

This surface mount resistor you suspect, which will be close to the dc jack, do you suspect its damaged physically?

Again for fault finding, to identify componets you need the original design drawing and more complex test equipment.

I'm going to go back to simple again, I came across a power issue with an Acer once and the dc jack looked undamaged and secure. I replaced it just as a precaution and this cured the fault. May have been one of the inner board connections that had a dry joint, who knows!!

I had a forum member once who had a GPU issue and she was looking for a repair shop on the internet and found the *Florida Motherboard Specialists* who could fix her issue. Turned out she lived a couple of buildings away from them. Very quick and reliable.


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## blombardo (Aug 22, 2010)

The surface mount resistor I identified is only a guess - because it has the same voltage as one of the three damaged terminals - so I know the power is flowing through it - but beyond that I don't know if its THE one responsible (and there are probably two other damaged ones) -- I'll have to send it to one of the companies that do this sort of thing - I had hoped to learn how to do it mySELF...

(oh and yes - I did replace the dc jack with another known good one... -- and yes I did mean the DC power )


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## night_shift (Sep 8, 2009)

Hey blombardo



> Otherwise I'm afraid the generic answer is 'motherboard failed - replace entire motherboard' (suckiest answer in the universe


I agree with you and its frustrating for us who would like to have a chance at repair down to component level. I have been down this road before not just in my spare time repairing laptops but also in my profession (industrial electonic tech).



> even though the parts I need will cost a fraction of a penny and someone will have a reel of 10,000 sitting on their shelf...)


.....and this rubs salt into that wound.

Trust me blombardo I have searched and talked to many people about laptop component identification and have had a few returns but not much. 

FYI the surface mount resistors if heated with a miniture hot air blower will just pull from the board. The procedure for fitting; is clean the contact area and using a solder flux mix place a small drop on the contact area, place the component on top and then reapply heat with your blower, clean with alcohol....done. Simple if we could identify the component though 




> 18volts + ground comes into the dc power jack - 2 wires carry the current about 4 inches and a plastic connector splits it into 2 18volt wires and 2 ground wires - they attach to the motherboard (where I have all good connections).


Is this the grey cable with the 4 conductors I'm looking at in the picture? Where does the other end connect, does this run back to your dc jack? Can you take a close up picture around PL15 if possible?

I share your frustration :sigh:


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## J03 (Sep 9, 2010)

blombardo said:


> http://h30434.www3.hp.com/t5/Hardwa...-battery-LED/m-p/165589/highlight/true#M19323
> 
> 
> Seems I may have found a company that has experience with this exact problem... if only their secrets were revealed to the public so I could avoid paying a $100.00 + fee for a 5 minute repair job...
> ...


You'd be better off sending it to Precision Division. They offer the longest warranty of anyplace I know. Also in Florida.


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## blombardo (Aug 22, 2010)

Interesting to know - I actually have been hoping to find a CHEAP oscilloscope that has a decent set of specs so that I can attempt to fix this mySELF... I really don't want to put out 100 bucks for a repair that I'm perfectly capable of doing... The only problem is all the DECENT oscilloscopes are going from 5k to 30k -- the ones in the few hundred dollar range are pieces of scrap in my opinion... 

Anyone have a link to some off shore Chinese company selling these dirt cheap?

IF I can fix it myself - I WILL post exact directions here on how someone else can repair this problem - at least on this board...


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## booburke (Sep 14, 2010)

This is a common issue with the dv8000. My mother in-law gave me hers, so I am hoping to find a cheap fix as well. Used MBs on ebay are 130ish, however, you are taking the chance that these will have the same issue, now or in the future.

I hope you are able to find the issue. At some point I'll open it up and see what I can do, but I am not hopeful.


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## blombardo (Aug 22, 2010)

I tried to offer a local pc tech the job of fixing it (as he has an oscilloscope and I dont...) he was able to figure out which part was bad - the problem now is finding that pin-tip sized component - and installing it when its so small tweezers would be huge in comparison. As he has no supplier for the parts he could not fix it - so I'm not out any cash...

thanks to the member of this forum who sent me the flow chart; if only they had PART NUMBERS on it... even IF I can find a supplier willing to sell me (one instead of 10,000) I will not know what part to ask FOR...

(It is too small to get any identifying numbers)

I think I'll be forced to mail it to florida Motherboard specialists (who will charge me about 100 bucks - plus 20 or so in shipping); If I do that I'll post an image of the board - zoomed into the damaged part...

Anyone here know of any friendly parts suppliers? lol


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## patton (Dec 29, 2009)

Some times you can de-solder parts from an existing mother bored if you have one handy.


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## blombardo (Aug 22, 2010)

I'm afraid that in - this case - the smallest Weller tip is the size of two of the damaged chips in question. I have no way to remove and reattach the parts - and no spare parts to use... the board will have to be sent to a professional shop with a parts inventory and some tiny automated machinery...

Thanks for the idea.


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## kgrantkey (Nov 12, 2011)

I wish someone could give a clue on this problem.

I have two motherboards, 1 hp presario c300 and one c500 that have this exact problem. They work on battery power but will not work with the 19v DC from the external power supply.

Like you my readings at the battery input to the motherboard are not what they should be.

I suspect it to likely be a voltage regulator, possibly the one in position PU2 which is a 92a04 4.8v regulator or maybe the shottkey rectifier pj1/sx34 in location PO1. 

I have no schematic diagram/component layout for the motherboard or a flow chart, theory of operation with which to isolate the defectiv component.

I decided to post here in the hope someone would have more info to help with what seems to be a common fault with the hp compaq presario in the model range.

I have seen many posts that talk about the flashing lightning bolt on the front of the laptop and the flashing power led and assume many of those posts to be linked to this issue.

I bet there are technicians out there that have repaired this on these motherboards numerous times.

Maybe one will see this and enlighten us.


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## kgrantkey (Nov 12, 2011)

I have seen this motherboard for less than 75.00 which is not bad. There are about 3 or 4 motherboards that will work in this laptop. 

If i decide to buy one i will make sure it has the 945gml intel chipset rather than the 940 that comes equipped on some of the motherboards. 

The 945 chhipset supports the core 2 duo.

So if you do purchase a replacement motherboard make sure you get one that will allow you to pop in up to a T7600 for some extra horsepower.


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## kgrantkey (Nov 12, 2011)

After a little more reasearch there is a 24 pin ic on the edge of the board near the battery terminals that is a lithion battery charger control chip.

It is a 3887-0705, battery charger chip. I couldn't replace that chip if i had a spare as it's just to small. 

I think I'll save up and get a replacement motherboard.

Another idea i had was to find a dead battery for this modle, break it open and attach a 12 power supply to the two main pos and neg terminals on the ckt board inside the battery. It will change the 12v to 10.8 volts supplied output for the laptop to operate. But that defeats the purpose of a laptop.


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## blakeenterprize (Nov 21, 2011)

tiny smd component replacement can be very intimidating at first, when you know some tricks of the trade it can be still tough but not impossible. even with the basic equipment.

removal of smd resistors and capacitors would be easier if you had soldering tweezers but with just an iron it is still easy... you have to flux both contacts.. heat both sides by convection.. no need to get the tip in between the component and board. just place it on the metal end till the flux activates ie smokes up. then alternate sides lifting that end with something each time.. untill you can remove it... shouldn't be that bad with the right setting.. and resisters arn't very temperature sensitive.. 

remove another resistor from the board that looks exactly the same. test that resistors resistance out of board.. order the replacements.. all you need is the equivelent standard... 

placing on the board is tedious but at least resistors don't have polarity.. so grab it with tweezers.. flux and tin one side... then i solder them to the end of a surface mount resister.. the long metal end is used as a pick.... then i flux and tin the other end... flux and tin both contact points on board.. using the pick i set the resistor where i want it... solder the other side to the board.. when its there you can remove the pick and solder the remaining side...


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