Learn Laptop motherboard Repairs From The Experts!
Less Theory, More Practicals!
Get Trained For Your Future Today!
Open the door to an illustrious career!
Join now and unlock your technical hurdles!
Here I made a mistake, I didn't pay attention of the voltage of DNBSWON, this mistake waste me the next few days time. It should be 3.3V, but only about 1V. Change EC as usual, because I thought the EC has problem. Then the big trouble comes - it auto power up once I plug in the power but stop in 0.04A current. Check and find no S5_ON signal, which indicate south bridge has problem, so change south bridge. But still same problem and still no S5_ON. I find that the EC I change is kb3926A rather than kb3926C. In most case, this is no problem but in very rare occation... So I find a 3926C and put on. Now the motherboard is back to the same problem while I first start to check! So I change a wrong EC and this time I change a correct one, and also EC has no problem! Because EC will start to read bios once the power plug in(not as people think, once you press power button). I check BIOS chip, BIOS_CS should have a countinue wave form but it just one stright line. BIOS chip is faulty, I replace the BIOS chip and it works perfect.
Question:Is it possible to replace the USB port/controller? Okay, so the USB ports seem totally dead, no power at all. It is because some soda was spilled on it (I presume, at least, may be randomly related with something else). I also corrupted my OS X install, have to reinstall freshly. Now, I haven't reset the SMC or PRAM yet, and that's the first thing I'll do (however as there's is no 5V power, I doubt this will fix it, correct me if I am wrong). However, if that goes sour, and won't fix the problem, what are my options? Here's how I was thinking: Firstly, can someone tell me all the devices I should be seeing in the system profiler under USB? Also, isn't it so that a central USB controller also handles the internal keyboard and iSight which still work perfectly, meaning that only the ports themselves are damaged? Let's presume so, and that the USB controller chip is still okay. Should I just replace (desolder old, solder new) the female USB ports, or could the problem lie in the connection between them and the USB controller, and if the latter, how would one go about fixing it? Answer: I think you need to start with the physical USB port/s of the system.Remove the battery pack & disassemble your system. I would clean the area where the soda spilled thoroughly of any soda that might be still present. Use distilled water on cotton swabs (Q-Tips) to clean things and then use isopropyl alcohol to then treat the areas to act as a dryer and look for any damage. If the USB outlets are damaged (corroded) you'll need to replace the full logic board as they can't be easily removed without damaging the logic board. Replacing any of the components of the logic board requires very special SMT tools and not really serviceable.
The fact AHT does not find any problems implies your circuits (USB controller) are AOK. So most likely the USB sockets have become damaged. And, Yes, your USB devices do show up under the Apple Profiler application if they are seen. You also need to take power sources away from it (battery, etc...) and clean up after the liquid damage. Yes there is only 1 USB controller. However, the USB controller has 4 channels operating 8 deices (2 per channel), without looking at the schematics I couldn't tell you if both ports are on the same channel, though I doubt it. It is possible for 1 channel to be bad on the USB controller and the rest to function properly. The USB specification is about data transfer rate and not about amperage to power or charge something. Please tell us more about the devices you have attempted to hook up to the USB port(s). On the USB ports there is, among other things, a 15K OHM resister that creates the amperage for the port (on all the Apple motherboards I have inspected). It is a 402 SMD package, less than 1mm in length, and you really need a stereo microscope to solder it in. The actual physical port you attach to is a rarely at fault without it being physically damaged to the point of not passing visual inspection.Click Here For Complete Course Contents Apple logic board has a lot of SMT components near the sockets that a heat gun will disturb. Focus on cleaning the soda spillage and then see where things are. One thing I did forget to ask is your USB device/s powered or unpowered? Your USB I/O could be OK, but, the power side of the port could be damaged. Try a powered device or hub to see if thats your problem. LAPTOP/MONITOR SCREEN VERY DIM OR DOES NOT ILLUMINATE A question I am often asked is "How can I tell if the backlight or inverter has failed on my laptop/monitor as I can only just make out an image?" The answer is that there are several causes of a dim display or the failure of a backlight to illuminate the screen. As most people are aware, inverter and backlight failure are the most common. Other causes are:- a faulty or damaged LCD/Inverter cable, Faulty motherboard and a faulty screen. Firstly try the obvious! There is a little switch usually located near the hinge which switches the display off when the lid is closed. This can sometimes get jammed and is easily overlooked. It might simply be a question of unjammimg it or making some sort of repair to it. Most laptops are able to toggle between an external display and the built in screen. Sometimes the laptop can get confused so it is worth toggling between external and built in screen. As most have several different settings it is worth doing this several times. If the laptop screen flashes when you do this it would indicate that the inverter is trying to start the backlight. This means that there is a good chance that either the backlight or inverter has failed but does not totally rule out the other components. It may also be worth resetting the bios as these settings can sometimes be lost especially if the cmos battery is on its way out or has been disturbed. Unfortunately, unless you are a qualified electronics engineer it is very difficult to test the individual boards and components and fault location is basically a case of substitution until the problem is cured or you decide not to spend anymore money on it! Laptops usually only have 1 backlight so obviously if the backlight fails there is no illumination of the screen but the same result happens if the inverter or one of the other components mentioned above fails! In the case of monitors, most monitors have 2 or more backlights and it would be unusual for all the backlights to fail at the same time so if you have no illumination of a monitor screen but the power light is green then chances are the inverter has failed. A failed backlight on a monitor will result in one half of the screen appearing brighter than the other half. BACKLIGHTS Backlights can be tested by connecting them to a known good inverter. You can use one of the inverters they sell for case moding. Just provide a 12V input for it and connect your backlight to one of the output sockets. If your backlight illuminates then it is OK and the fault lies elsewhere. A pink or red hue to the screen is nearly always a sign of a failing backlight and if this happens it is well worth replacing the backlight as the only other thing that can cause this is a faulty screen. Remember backlights work on an AC Voltage of around 1000v and although the wattage is very small can give you a nasty shock and could prove fatal if you have a pacemaker or similar. INVERTERS We now come to an item that can only be tested by a qualified electronics engineer or simply substituted. There is usually a small fuse located near the input connector. Check this for continuity. Depending on the inverter there can be several inputs but it is worth checking the input voltages. Basically you will have a positive and negative feed plus a switching voltage and a brightness connection. The basic voltage for powering the inverter is usually the same as you laptop input voltage but the switching voltage may be as low as 5 volts DC. The brightness voltage can be anything from 0 to 5 volts but normally full brightness is acheived with 0 volts so don't worry about this. Unfortunately inverters often have up to 20 or more connections and may incorporate circuits which show battery charge status, on/off status and almost anything else you care to name! As wiring diagrams are rarely available its impossible to know which connection does what. It is possible by a process of elimination to work out the main positive and negative terminals and you may often find there are several of these but the rest is pure guesswork. If you have an analogue multimeter, set it to the highest AC reading (usually 1000V) and check for an output from the inverter. Initial start up voltage will probably exceed 1000 volts but normal running voltage should be below 1000 volts depending on the size of your screen. Look for a voltage in the region of 400 - 900 volts. Obviously if you are getting a good voltage here then your backlight has failed. Otherwise I am afraid it is a case of replacing with a known good inverter to see if this cures the problem. (If anyone knows of a foolproof way to test an inverter please enlighten me) LCD/INVERTER CABLE Check this cable carefully for damage especially in the hinge area and make sure the connectors have not worked loose. It is possible for the wires to break internally with no obvious signs of damage so check the continuity of the cables. A faulty LCD cable can even result in your laptop not switching on. MOTHERBOARD The motherboard sends a signal to the inverter board telling it when to switch the backlight on. If there is a fault on the motherboard then the inverter board will not receive a signal and therefore not switch the backlight on. It may be possible to check the input voltages to the inverter board with a multimeter but if you have eliminated the previous items I have found this to be quite a commom fault. NB If you connect your laptop to an external monitor and get a good picture this only proves that the video card is OK, there could still be a fault on the motherboard which is preventing your screen from illuminating. SCREEN It is possible for a faulty screen electronics to result in the backlight failing to illuminate. This is rare but can happen and if you have eradicated the previous items is the only possibility left. Click Here For Complete Course Contents