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Old 10-09-2021, 10:39 AM   #1
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Default Help troubleshooting ASUS vivobook e406ma

Hello everyone.

I have this laptop and there is some kind of a problem with it.

Symptoms - when connected to a power supply, the power led goes orange. The led on the power button goes white.
Power consumption is around 3W
No image on both internal and external displays.
There is power on the USB.
Seems to be reacting to the power button ( when pressed for 10+ seconds it enters in a "boot loop" mode - power consumption switches between ~0.5 and ~3W, the leds turn on/off with the consumption ).
The battery circuit seems to be working fine ( when the battery is full, the power led goes white ).
I tried programming the bios IC with several different dumps ( 2 extracted from the official bios update files - e406ma+e406mas and one dump downloaded from the internet - e406ma ) and no success ( even one of the dumps just makes the board to go directly in power boot cycle ).
All but one power rails seem to be working. Only on +VCGI(?) there are 0v.
I injected 0.6 volts and the consumption is something like 100-200ma.
Checked the two mosfets and they seem to be fine (no dead short on any of them ). The resistance on the 470uF cap on the rail is 30ohms though.
I could not find any schematics or boardview for that particular board, so I'm using for reference the boardview for e203na, which seems to share similar ICs.

So any ideas for how to proceed?
Attached Images
File Type: jpg DSC08901.jpg (969.6 KB, 16 views)
File Type: jpg DSC08902.jpg (918.1 KB, 12 views)
File Type: jpg DSC08901-1.jpg (989.8 KB, 11 views)
File Type: jpg DSC08902-1.jpg (935.0 KB, 11 views)
Attached Files
File Type: rar Asus E203NA_r3.0.rar (70.3 KB, 25 views)

Last edited by madan1; 10-09-2021 at 10:43 AM..
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Old 11-01-2021, 12:20 PM   #2
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Default Re: Help troubleshooting ASUS vivobook e406ma

And to update the topic - while doing some measurements, I managed to shorten something ( most likely the battery charger IC, which is also responsible for the standby voltages ). I got lucky and won a cheap replacement board with physical damage around the power input ( scraped and damaged smd components ), was able to replace the missing and damaged parts, which fixed it. Just for fun, I installed the bios IC from the original board, to the fixed one and it started to fail the same way - no video and no voltage on the VCGI, which leads me to believe that this was the root cause of the original problem.
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