Review if there is a coin cell battery on the board. If yes, test the voltage to ground of that battery. This battery may need to be replaced with a fresh one. Often, the ec is powered by the coin cell battery when the main power rail is off.
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Dear mon2,
Thank you for your help. There is no coin cell battery on this board.
Regards,
mkdjComment
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Remove all power. Meter in resistance mode. Measure the resistance to ground of this J5 trace for the EC power rail that is absent. We are testing to see if the rail is being shorted so the voltage is missing.Comment
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Dear mon2,
Value of resistance to ground is 7.5 kOhm. So there is no short to ground on the +3V power rail.
Regards,
mkdjComment
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Dear all,
I am still trying to figure out what the problem on this specific board is. There is no short on the +3V power rail. But it is at 0V. Also, I don't know how the +3V signal is created, so I can't diagnose anything. Schematics are not available, and I am stuck with the boardview, which does not help me to figure out how the +3V power rail is created.
I am keen on having any information on what to do now. It is a nice machine, and I would like at least to understand how the +3V signal is supposed to be created on this particular board.
Regards,
mkdjComment
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Review the actual regulator and its pinout for the +3V power rail. There should be an EN (enable) pin on this component. This EN signal will be created by either a resistor based voltage divider OR driven by the EC controller. The EC controller is often backed by a coin cell battery or similar. Just this week alone, had 3 cases of where the coin cell battery caused the logic board to appear to be dead. Replacing the battery fixed each of the 3 cases. Do investigate this if you see a coin cell battery.Comment
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Dear mon2,
I can't find the actual regulator for the +3V rail on this board, which is why I am stuck. Also, there is no coin cell battery on this motherboard.
However, I have news. As the board when plugged in is taking 20mA, I tried to use my thermal camera to see if there was a chip heating. And I have found that something small is heating next to a PWM controller. Reference of the chip is MP2884AGU, and datasheet is here: https://www.alldatasheet.com/datashe...MP2884AGU.html
I don't know exactly what is heating (the chip itself or something next to it) because my thermal camera has really low resolution and parallax issues. I tried to use alcohol and a freeze spray to locate precisely the heating element, but without success. I guess it is not heating enough to be detected.
Could this chip be the one creating the +3V signal? And because it is heating, it would mean that it does not work properly, and can't create the signal?
Or is the fact that the chip is heating a normal behavior?
Regards,
mkdjComment
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No, this regulator is not the one responsible for the +3V always on rail. The datasheet shows this regulator as a multi-phase regulator meaning it is intended for much heavier loads such as the CPU or GPU. Much like humans, more manual labour can be performed if multiple people are involved instead of a single person, this regulator takes turns turning on one power leg of this multiphase output then turns this one off and turns on the next and so on. Each take a quick on/off action to not burden the single leg. It may be normal to see a temp rise on this regulator since the current draws are heavy.
The board is only consuming 20mA so very little current draw. As a comparison, a LED will be 5-10mA for a signal led.
Locate a known component that makes use of the 3v3 rail. Place one meter probe there. Meter in diode mode. Touch your meter probes to confirm there is a tone beep. Be sure there is no power to the board. Now probe each inductor on the board till you hear a tone beep. The +3v3 regulator should be near by. Try this approach.Comment
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I'm working on my sister's laptop: Asus VivoBook F510UA-AH51 - The motherboard died so I replaced it.
The original board was:
ASUS X510UNR REV 3.0 A
The replacement board is:
ASUS X510UNR REV 3.0 B (identical except B vs A - I couldn't find an A board anywhere. Visually they are identical.)
It boots right up on the replaced motherboard and everything works fine on the new motherboard - but it won't run off battery. When I disconnect the charger it immediately dies. When I plug it back in and reboot the system - it still shows the battery at... -
I have an Asus TUF machine that doesn't run off battery. Runs off charger ok, shows orange battery charging light and shows battery is at 96%. Battery voltage is less than 0.5v though. It had a short on the 20v rail from a dead cap. Pic attached. Removed cap and replaced a dc in mosfet. Machine now powers and runs fine.
I have also replaced all 3 battery mosfets with no change. The 1st battery mosfet has 20v going in. Pic attached.
Does it sound like a battery ic problem, it has bq2470. Not sure if I should replace that as well at this stage as I'd need to order one.
Thanks.... -
Hello everyone
I have been working on this laptop mentioned in the title, it initially had a shorted capacitor. After I replaced it, the thing started working again, but there is still another problem. The laptop was running off a charger, the battery was reporting 96% charge... but when I unplugged the charger, the laptop died. I've measured the battery voltage - 0V. I think it is locked. (Screenshot from batterymon, below).
I've ordered a new 3rd-party battery, but I think there's something wrong with it too - the laptop boots, but the battery isn't charging. Also,... -
Hi everyone,
I have been working on a no power issue with my personal ASUS gaming laptop. It went dead a few months ago.
Some history:
Since then, I've found a blown mosfet on the GPU line which I replaced. It started up without a battery, then when I added the battery back it wouldn't start up again.
As a result, there were some blown components around the BQ chip. (The BQ chip itself - BQ24780S, the low side battery mosfet (shorted), and a resistor -> all replaced)
Now, with a new battery the system will start up and run off... -
Hi,
I have an Asus GA401Q which only works from battery power. That suggests the board is mainly fine.
The battery status is 255%, also with a brand new battery.
The BQ24800 was replaced since it showed signs that it was part of the problem, but possibly the battery was flat at that moment.
If I insert the 19V adapter in the DC jack and measure the current sense resistor's voltage it fluctuates between 0V and 19.5V and the keyboard backlight flashes (probably because the battery is almost flat. It does the same when I run the laptop from battery).
There's a...
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