Dell 7391 2 in 1 i5 10th gen

[ss45]

Hi I've got dell with no backlight
The display is pitch black but if I shine light into the panel, I can see image just fine.

I have check lcd LED power fuse, ok, voltage is around 8volt.

I don't know which pin is lcd backlight enable, so if anyone know, please.....

Since it is 2 in 1 touch , lcd panel is strongly glued to top panel, it's hard to take of and probe the lcd connector directly....

There is possibility that Lcd inverter MOSFET could be bad, which is a nightmare to replace, since I need to teardown the upper panel and LCD itself...

Any help appreciated.
Thanks

[mon2]

Re: Dell 7391 2 in 1 i5 10th gen

See attached. Meter in DC volts scale.

Measure the voltage for pins 1, 19-30. The pins 2-16 can be skipped since you can see the graphics / text on the screen with a flashlight - so the eDP data lines are working fine.

Post your measurements.

[ss45]

Re: Dell 7391 2 in 1 i5 10th gen

Thanks will check it this weekend

By the way forgot to mention.

When I first booted it, it prompted me to choose which model that PC is, there were 3 options 7791 2 in 1, 7591 in2 in 1, and 7391 2 in 1. I chose the last obviously, since this board is 7391

Also after that it gave me message that service tag hasn't been programmed.
After rebooting, service tag displayed in bios and back of bottom panel differs.

Quite a strange case... Haa anyone had this kind of experience ?

[ss45]

Re: Dell 7391 2 in 1 i5 10th gen

Here is the measurements

30-28 8.2v
27 x
26 1.5v
25 3.1v
24 2.3
23 0v around 125ohm to ground
22-19 3.3v

[mcplslg123]

Re: Dell 7391 2 in 1 i5 10th gen

Pin26 needs to be 3.3V.

[ss45]

Re: Dell 7391 2 in 1 i5 10th gen

Edit

Wrong measurement
Pin 26 is around 3.1v

So does this mean I need to disassemble the panel ?

[ss45]

Re: Dell 7391 2 in 1 i5 10th gen

So after opening the panel there was indeed blown fuse inside between 8v.v line and led driver. Luckily no short on the driver. Phew....... Replacing that fuse fixed it

Thank you all guys