Component Level Motherboard Repair (Not replacement)

会员521064

1) How do you diagnose the exact component failure?
Obviously, a burn mark is a dead give away, but what if there are no visual signs? Do you poke around with a multi-meter? With what voltage settings and how do you know what to look for?
2) Is it usually a bad capacitor?
badcaps seems to think so. What about a bad connection?
3) How do you perform the component level repair?
So you've found the bad capacitor or component, can you really solder a new one on without hurting the components around them? What's a good soldering iron for under $100?
Answers to your questions
Diagnose problem:
This is the hardest part in notebook repair. Basically, we measure voltages on motherboard and there are few power supply range from 1V to 12V on the motherboard. For example, north bridge needs 1.05V, 1.2V, 1.5V, 1.8V, 2.5V, depends on model of north bridge.
We also measure all sort of signals, such as PCIRST, CPURST, CLK. We measure the resistances of each AD line from north bridge to CPU/RAM.
We watch the current changing patterns to get rough idea where is the problem.
There are some simple steps to follow when checking a notbook motherboard:
1. make sure main system powers are ready, that is 3V and 5V.
2. switching circuit is ok, which involes IO/Keyboard controler, south bridge
3. power sequence is ok, which you can see the current jump up and down for few times.
4. all the necessary signals are not missing.
About Bad Cap
It happens but only about 10% in those motherboards need to repair, and it is the easiest fault to repair not matter if the cap was burnt or not.
Loose connection
Mostly happen on VGA chips, south birdges and the places close to CPU. Hard to troubleshoot and need lot experiences.
How to repair?
You need specialised tools. I have DC power supply which can display current change and set to different voltage and current output. You need Really nice soldering station, SMD rework station, BGA rework station, etc. I also have more than thousand schematic diagrams, all together about 10GB and you could not find anywhere in the net.
I have seen the video in youTub teach people how to fix VGA problem, and I guess you only have 30% chance if you follow it. My BGA rework station tutorial can perform up to 95% successful rate.
________________________________________

会员353305

我哭啊，我英语水平太菜了，看天书

会员401108

说得什么啊，字看不懂给个图也行，