Asus EeePad Transformer Prime TF201, MB: TF201, No video, no backlight

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Brand: Asus
Model: EeePad Transformer Prime TF201
Motherboard: ASUSTeK TF201, Rev.: 1.6
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Hello!

I'm working on the following tablet, which was previously repaired in another repair shop without success.

Noticeable signs of previous repair:
a) Poor soldering on the FFC conector near the Hynix memory chip. (This connector connects the charging port with the motherboard.)
b) Brownish black silicone in the bottom right corner of the Hynix memory chip. It was probably caused during the soldering of previously mentioned FFC connector with a hot air (pictures of the motherboard below).


The tablet came to me completely dead (the battery was not charged, no response to the power button).
After repairing the solder joints on previously mentioned FFC connector the symptoms are the following:
a) Battery charges normally (the orange LED lights during the charging and the green LED lights when the battery is fully charged).
b) When the power button is pressed the tablet vibrates, but the screen remains black (no video, no backlight).
c) The main chips on the motherboard gets a little warm.

Pictures of the motherboard:




Voltages to ground on the inductors and other components before pressing to the power button: (connected battery only, without connected charger)
Battery -> 7.63V
Pin 8 of BIOS chip -> 2.94V (chip is Winbond W25X40BVIG)
Power button -> 3.31V

Voltages on the inductors (inductors are marked with the numbers on the upper picture):
1 -> 0V
2 -> 0V
3 -> 7.63V
4 -> 150mV
5 -> 0V
6 -> 0V


Voltages to ground on the inductors and other components after pressing to the power button: (connected battery only, without connected charger)
Battery -> 8.21V
Pin 8 of BIOS chip -> 2.93V
Power button -> 3.31V

Voltages on the inductors:
1 -> 5.06V
2 -> 3.33V
3 -> 8.21V
4 -> 150mV (resistance to ground on this inductor -> 2MΩ)
5 -> 1.16V
6 -> 0V (resistance to ground on this inductor -> 44Ω)

Any suggestions are welcome.

Another question:
What is the function of the switch "SW6001" (it is visible on the right side of the second picture)?
It is not user accessible, once the tablet is assembled together.
When the switch is in the "ON" position, everything is as I described above, at the other hand in the "OFF" position the tablet is completely dead, the battery does not charge.

Hi.
Describe the power consumption (in miliamps) of the tablet before and after pressing the Power button.
Is there any difference in power consumption with connected display and without it?
SW6001 is probably a battery disable switch - that's the reason of "dead tablet" when it's in OFF position. More here: https://forum.xda-developers.com/showth ... ?t=1454625
Below polish translation.
================================================================
Witam.
Opisz pobór prądu urządzenia (w mA) przed i po wciśnięciu włącznika.
Czy jest różnica w poborze prądu urządzenia z podłączonym wyświetlaczem i bez niego?
SW6001 to prawdopodobnie wyłącznik zasilania bateryjnego, stąd tablet jest martwy gdy przełącznik jest w pozycji wyłączonej.
Pozdrawiam

Power consumption is the following:
(measured without connected battery, only power supply)
a) Stand-by (before pressing to the power button): 37mA
b) Turned ON (after pressing to the power button): 135mA, after about 25 seconds it jumps to 158mA

There is no change in power consumption with or without connected display.

You have right about the switch SW6001. I checked it again and it disables the battery only.

Thanks for the reply! Any further ideas?

Power consumption in standby mode looks a little bit too high.
Have you tried to connect tablet to PC? Is this device detected?
Have you noticed the difference in power consumption when you tried to run tablet in recovery mode?
Is there any picture when you connect the device to another display via micro HDMI to HDMI adapter?
BIOS image is currently unavailable, and I don't think that ASUS will share it. Firmware from ASUS support page probably doesn't contain BIOS image in any form.
Below polish translation.
=========================================================
Pobór prądu w trybie czuwania wygląda na zbyt wysoki.
Próbowałeś podłączyć tablet do komputera? Czy urządzenie jest wykrywane?
Czy zauważyłeś różnicę w poborze prądu przy próbie uruchomienia tabletu w trybie recovery?
Czy po podłączeniu urządzenia do wyświetlacza z użyciem adaptera micro HDMI na HDMI pojawia się obraz?
BIOS na chwilę obecną nieosiągalny, nie sądzę że ASUS go komukolwiek udostępni. Firmware ze strony wsparcia ASUS-a prawdopodobnie nie zawiera obrazu BIOS w jakiejkolwiek postaci.
Pozdrawiam

xamledyD написав:Have you tried to connect tablet to PC? Is this device detected?

When the tablet is turned ON the PC detect it as "APX" device, but it can't find driver for it.

xamledyD написав:Have you noticed the difference in power consumption when you tried to run tablet in recovery mode?

In this case the power consumption is 155mA and it remains at this value.

xamledyD написав:Is there any picture when you connect the device to another display via micro HDMI to HDMI adapter?

No, there isn't picture on the external monitor as well.