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Laptop Motherboard Diagnosis/Repair (No Power)

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October 22, 2010 10:55:12 PM

I recently got a job (1.5weeks in) as a 'laptop/component repair tech' in a small shop and I'm in over my head. I've replaced/re-soldered AC/audio jacks before and can strip down a laptop to diagnose components but not much beyond that (did one solder reflow in my oven). The tools they had there were an old school multimeter, solder, iron. I brought a desolder pump, capacitance meter, copper braid.

Last two machines (both Toshiba satellites weirdly) I got were like this:

No power, no lights. Stripped down didn't help. Adaptor OK, AC jack OK, Fuses were all ok. Visual inspection gives me nothing (Burned northbridge or some such would be noticeable)

From there where do I go? I guessed it needed a reflow since I didn't have any other brilliant ideas. I haven't been able to find schematics for many boards either which would help (I could check the power IC possibly?).

If anyone here is familiar with this type of work I'd really appreciate talking you for as much as you'll have me. I like the work and I am learning a lot but I'm probably going to lose my job soon, and I'm not sure what resources I can learn from (other techs there can't even solder... had no idea what a de-solder pump was). If anyone has any bright ideas about online resources I'd appreciate that too (troubleshooting laptops lead me here more often than not). Also wondering what cheap tools you might suggest I add to my line... obviously not a rework/reflow station or anything.... I am only getting minimum wage and prefer eating to not :p 

a b V Motherboard
October 23, 2010 8:55:55 PM

Ok, here's the deal-laptops are not made to be worked on. Desktops are pretty easy to work on and have few integrated parts, unless you're talking about budget models and dell, gateway, etc. Laptops on the other hand are highly integrated, so if there's a failure its likely that the whole mobo needs replacement.

I would invest in a pc repair kit, they sell them on newegg for 20-40 bucks, depending on what you need and/or willing to invest. They are great, and typically have everything you will need.

If a laptop is out of warranty, then the user is likely out of luck. There's a couple things to check as you surmised; the power cord/powerbrick, the adapter jack, and power button. If all those things check out, it is likely a motherboard. Replacing motherboards in laptops is very expensive, at this point it is best to tell the client that you can retrieve the hard drive or the data itself but they need to get a new laptop.

Not good news for anyone. However if it is still within warranty, manufacturers are pretty good about replacing motherboards. I had one die on my Compaq and they had it shipped back to me fairly quickly, and it was the motherboard as I surmised.

The reason for failure can vary, but many laptops die because of heat generated by the cpu or video chip. If a client needs to replace a laptop, I would advise them to invest in a laptop cooler to avoid that issue in the future.

You are going to waste a great deal of time trying to troubleshoot to the component level. Nobody does this, if you can't replace a switch or card to fix this, then there isn't much you can (or should) do. Once you have eliminated all possibilities, don't be afraid to say its a motherboard failure and move on. Believe me, if you are only getting minimum wage for PC repair the folks paying you are not expecting much. Just learn to troubleshoot things quickly and everyone involved will be happy, people don't expect their PC to be in the shop for a week or two.

I recommend you pick up a simple computer repair book and read up. Also web sites like toms provide invaluable insight and advice. Good luck.
October 23, 2010 11:27:15 PM

I can diagnose most any pc problems down to the component level.... thats really easy.

And without a SMD or BGA rework station I likely cannot fix a ton of issues since northbridge problems are fairly common.

Things that are likely worth solving:

Bad capacitors. Decently common and the parts only cost a few cents.
Most of the ICs on board... 4-20 pin jobbies such as the power ic do fail and are swappable for less than a buck or so
Blown fuses. Easy to diagnose easy to replace. This is a definite.
Any and all damaged jacks. Power and audio being the most commonly broken.
Resistors. easy to find easy to replace. cost is in pennies
Transistors and diodes can be more problematic to diagnose and fix but they too are cheap and swappable with just a soldering iron.
Obviously i can swap cpus so I should be able to diagnose that as well.

I can't fix:
Northbridge or the vga chip without a BGA rework station so that is out of the question even if i have to be able to diagnose it


I found an example of the dude that does pretty much what is expected of me:


"Machine: HP G6000(same mainboard as V6000)
Problem: not power up

The machine has been water damaged. It does not have system standby power, which are 3V and 5V.

Check Max8724(the battery charging chip) first, because to make system has standby power this chip must work correctly. This is a 28 pin chip, we only need to test 1, 2, 4, 8, 10, 11 pin. They are VIN(main power for chip), LDO(provide 3.3V for chip itself in order to set REF voltage, also provide signal to drive 2 MOS to charge battery), REF(set reference voltage of the chip), SHDN#(enable/disable chip, a switch), ACIN(indicate the power supply has plugged in), ACOK#(power adaptor ok with mainboard).

Everything ok except 10 pin, ACIN is 0V. This is incorrect, mainboard doesn’t detect there is an adaptor! Trace it backward and find it is very simple – mainboard use 2 resistors to pull the input voltage(19V, directly from dc socket) down to about 4V, so test the first resistor and find it opened. Change it and 3V/5V power come up and mainboard be able to switch on.

Then the trouble start when I try to charge the battery. The charging current never go beyond 0.15A and after 10 seconds the charging light start to flashing. Also can’t switch on from battery. First, change Max8724, still same problem. Next check all the resistors around max8724 and change it if it has any sign of watering, still no good. Then change KB3926(EC/KBC, chip monitors the statue of battery), still same. This is the fault that I never dealt with before.

Decide to check MBDATA and MBCLCK, 2 signals that send battery information from battery to KB3926 before I give up. I find the MBDATA is short!

Finally, find there are 2 pins stick together on CN10(the connector of multimedia switch board). Fix it and it start to charging battery. Switch on with power adaptor, ok. Remove the power adaptor once switch on, battery keep the mainboard running, ok. But still can’t switch on from battery once remove the power adaptor. Think, think, do I miss something here or there? Oh, the CMOS battery not installed, put the CMOS battery back and everything work perfectly. The battery part of troubleshooting takes me about 3 hours.

Remember, system may not run if you don’t have CMOS battery or CMOS battery is low for some AMD cpu mainboard.

I wrote this just help people who interest in repair mainboard have idea how to check the problems on mainboard."
Source: http://forums.whirlpool.net.au/archive/1223566
November 23, 2011 11:04:22 PM

buzznut said:
Ok, here's the deal-laptops are not made to be worked on. Desktops are pretty easy to work on and have few integrated parts, unless you're talking about budget models and dell, gateway, etc. Laptops on the other hand are highly integrated, so if there's a failure its likely that the whole mobo needs replacement.

I would invest in a pc repair kit, they sell them on newegg for 20-40 bucks, depending on what you need and/or willing to invest. They are great, and typically have everything you will need.

If a laptop is out of warranty, then the user is likely out of luck. There's a couple things to check as you surmised; the power cord/powerbrick, the adapter jack, and power button. If all those things check out, it is likely a motherboard. Replacing motherboards in laptops is very expensive, at this point it is best to tell the client that you can retrieve the hard drive or the data itself but they need to get a new laptop.

Not good news for anyone. However if it is still within warranty, manufacturers are pretty good about replacing motherboards. I had one die on my Compaq and they had it shipped back to me fairly quickly, and it was the motherboard as I surmised.

The reason for failure can vary, but many laptops die because of heat generated by the cpu or video chip. If a client needs to replace a laptop, I would advise them to invest in a laptop cooler to avoid that issue in the future.

You are going to waste a great deal of time trying to troubleshoot to the component level. Nobody does this, if you can't replace a switch or card to fix this, then there isn't much you can (or should) do. Once you have eliminated all possibilities, don't be afraid to say its a motherboard failure and move on. Believe me, if you are only getting minimum wage for PC repair the folks paying you are not expecting much. Just learn to troubleshoot things quickly and everyone involved will be happy, people don't expect their PC to be in the shop for a week or two.

I recommend you pick up a simple computer repair book and read up. Also web sites like toms provide invaluable insight and advice. Good luck.



Hello All, this is our first post and I have read a lot here and in other forums. So I wanted to try and clear the air and help people out who really want and or need the help. First off I want to say that because of people talking about stuff they know nothing about they think it cant be done or doesn't exist, this is ignorance at its best. Folks dont comment on things you know nothing about, educate people or yourselves and double verify before posting something that just is not true. I will do my best in giving the most accurate information possible that I can. I'm a technical Manager/Director for a large volume Component Level repair facility located in the heart of Silicone Valley. What we do is simple, it is component level repair? What does that mean? It means on any motherboard we can replace or repair on a part soldered to the board, we can create traces, jump traces, replace SMD components, Caps, BGA chips, etc...What we do is a niche and there are less than 5 of these companies that do what we do in the entire US. However, less than two do exactly what we do with the success rate in which we do it in the US. Most of the eBay companies do physically do it, they send it to us but advertise they do. You will find us their as well, and most will copy or mimic our ads, I will provide a link below for you if you need. Or if you have questions you can call us as well. What others don't have that we do, is a physical business address, business license, Insurance(liability), also we are a member of the Electronic Bureau of Repair. Most of these companies have none of these credentials, in addition we have been re-balling chips for over 30 years. Keep in mind this is before laptops even hit the seen. We do most of our business (80%) for Laptop Repair Companies across the US. We are located in 2 areas in the Bay Area (Nor Cal). The first is located in South Bay (silicone Valley), and Also East Bay, Concord Ca. There are a lot of fly-by night companies and you very much have to be careful, I would look for companies with a repair rate of at least 99.1% or higher and over 400 in feedback. Why? because they have been around and at least have an idea of how to do business, it takes awhile to get 400 in feedback. You want to make sure that no one is scamming you, some of the horror stories I have heard form customers is unreal. Don't buy anything less that $100, you will be sorry. If you buy any ads that are less than $30 be prepared for them to call you and tell you it will be well over $200. The above post has accuracies, as well as some of the other posts. We currently have every single laptop brand you can think of in our shop for repair (so none are impervious to failing) and we do 30-40 repairs a day. I assure you that all laptops, even the most expensive Alienware or Sagers, Mac Book Pro's, and or high end dells (XPS series) will eventually die from a video chip failure when playing high end video games; there are numerous reasons that factor into this. Video Failure doesn't mean it can't be brought back: It can through a process of re-balling the video chip and or replacing the video chip if it is bad due to heat. Re-flows don't work it is a band-aid fix. If you have heard this term disregard it, if you need reasons I can provide it in another post.

In closing some of people are left to believe that the laptop came out to replace the desktop, which is just not true it will never do that. Every laptop brand and make will have problems, it's just a fact and we repair them every day. Most laptops are used improperly as well, they do not provide good ventilation and in most cases are smothered by their users in every day use. A lot of laptop repair companies who don't know this work can be performed, tell people just to buy a new one. What kind of advice is that?

We test and work on everything we report; we do not read Laptop company's sites and give information based on what they say, or what we here from Google, forums, or YouTube. In most cases there information is wrong and speculation based on what they have heard at best from someone else. Most of these people don't repair laptops, we do and certainly they don't repair on the same level as we do. Most people that do laptop repair have this work subbed out and it's up coming to us anyway. I hope for the moderators I stayed on point, for this topic and didn't get off topic. Mostly laptops, to produce what there larger counterparts do, will generate a lot more heat; thus rendering its uses limited. There is plenty more on this subject of Laptop repair as obviously just in this case I have said a lot, some of this is very hard to explain in short paragraph it can be very complex.

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