No visdeo ASUS X580

[dclass-pro]

Hi guys, an asus vivobook with X580VD REv2 mainboard arrived in the laboratory and it turns on and I have video on the hdmi output but no on the internal monitor.
The problem happened after the internal monitor flex cut and shorted out. I changed monitor and gflat and setsso problem, I have nothing on video, I changed bios and same thing. From the diagram I checked and on U4501 I have 3v input but 0v output and on pin 3 I have about 0.14V. On the display connector on pins 26 27 28 I have 3V and on pins 36 37 38 I have 19v, what can I check?

[mon2]

Re: No visdeo ASUS X580

What is the voltage to ground at pin #1 of U4501?

U4501 is an active high load switch so pin #3 has to be a logic '1' (high) to enable.

The output voltage from this load switch is powering the eDP pins 26..29.

So the voltage level should be the same at each label with netname of +3VS_LCD.

[dclass-pro]

Re: No visdeo ASUS X580

on pin 1 have 0,14v and pin 3 is 3,3V

[mon2]

Re: No visdeo ASUS X580

With care and flux, remove u4501 off the board.

Then check again if the voltage on pin #3 of u4501 pcb pad remains.

[dclass-pro]

Re: No visdeo ASUS X580

yes confirm remains 3v on the pin of the printed circuit

[dclass-pro]

Re: No visdeo ASUS X580

i tried to change u4501 to a new one but the result is the same

[mon2]

Re: No visdeo ASUS X580

Does this lcd have a touch panel? The same pin is being used for the touch panel interface over USB.

[dclass-pro]

Re: No visdeo ASUS X580

no it doesn't have a touch panel

[dclass-pro]

Re: No visdeo ASUS X580

but what do you think is the problem? shouldn't pin 3 be high? because from the diagram I see that the chipset manages it...

[mon2]

Re: No visdeo ASUS X580

Trying to understand the purpose of U4501.

U4501 is a load switch (aka solid state relay / switch) that should enable ONLY when the EN pin is a logic high = '1' = 3v3.

Then the input voltage will be passed onto the display panel but you always have 3v3 present on the LCD panel so what is the purpose of this switch?

Also, EN is a logic LOW so this switch is OFF.

From is this voltage being supplied onto the LCD pins?

Remove all power and check the resistance to ground of pin # 3 on U4501.

Also, then use DIODE mode on the meter. Remove all power.

RED meter probe, yes RED to ground.
Black meter probe to pin # 3 of U4501.

Correct that the PCH is driving the enable pin of U4501.

[dclass-pro]

Re: No visdeo ASUS X580

between pin 3 and ground in diode mode I have 0.590 on the tester

[mon2]

Re: No visdeo ASUS X580

So pin 3 is not shorted with this diode reading.

[dclass-pro]

Re: No visdeo ASUS X580

exact and therefore what may depend on the fact that I have no video on the internal monitor?

[Bartoloni]

Re: No visdeo ASUS X580

OMG, i have the same motherboard and the same issue... destroyed LED panel.. and video output only on HDMI ... i was thinking was the GTX1050 to reflow, but after this nothing changes.. i also noticed an high frequency noise coming from the GPU when LED panel is connected