Hi @donfurlan ,
Here’s some images taken from the schematics for the motherboard.
First check if there is power on the eDP connector pins 21-22-23. This is the VIBL12 power supply for the backlights.
If there is no power there then check the input pin 5 of U9. If not there check resistor R361.
If there is power on the eDP pins then you may have to check the backlight enable circuit as there is always backlight power to the panel but it is turned on and off in the panel by a signal on the Backlight ON lead connected to pin 25.
The lid sensor is just one component that can turn the backlights on or off by sending a signal to the motherboard chipset which then places or removes a signal voltage on the Backlight On lead
(click on images to enlarge).
Hopefully a start
Hi @donfurlan ,
It seems as though the power to the backlights is there all the time but relies on the lid switch telling the chipset that the lid is open so turn on the power to the lights.
I can’t see it from your image but the lid switch is connected to pin 6 of JBTN1 (power button board) connector so presumably when the lid is closed it appears that either a voltage signal which is on pin 5 is connected to pin 6 or perhaps an earth from pin 7. It could also be that the voltage signal (or earth) is removed when the lid switch operates as I don’t know which way it is and the circuit doesn’t show.
The voltage on pin 5 comes from fuse F36. I think that the voltage should be 3V but not totally sure about this.
Here’s an image showing the lid switch connection and also the fuse etc. The image on the right is just to show where it gets into the chipset which will be hard to measure but try measuring at D801 (both sides - test the diode as well) if you get any voltage/earth condition changing on pin 6.
(click on image to enlarge)
Note: I don’t know if it is a magnetic switch or a light sensor switch so if you measure between pins 5-6 (6-7?) of the button board connector it should change if you wave a magnet over it or cover it up to stop the light. If it is a sensor than you may have to have power connected for it to work whereas a magnetic switch may be mechanical in operation.
If you get no power on pin 5 check the fuse. If you get power on and off (switch operating/releasing - again I don’t know which way but it should change state) check that it gets through the diode.
If you prove that the switch is working OK check and you get power on/off? at pin 4 of U9 when the lid is open and closed perhaps U9 is faulty as it needs to turn on to connect power to the backlights.
Sorry to mislead you before but this one is different to others I’ve worked on it the past.
Also ifixit has an option to post images in your QUESTION, you can’t post them in Comments. Here’s how to do this Ajout d'images à une question existante
@donfurlan
I’ve been fixating on the lid switch and remembered that you said that there was no voltage on pins 21, 22 & 23 on the video cable connector so I thought it may be worth checking back from the video cable connector instead of forward from the lid switch, if you get what I’m saying.
Doing it this way I found that there is a fuse in the backlight power supply (eventually found it). Check if fuse F7 is OK.
If the fuse is faulty, search online for 0438003.WR 3A 32V ceramic fuse to find suppliers that suit you. Here’s an example to give an idea of the cost. Unfortunately with this example the minimum order is 10 pieces but it is hard to just get the one fuse. You may have better luck.
The fuse is an 0603 smd size i.e. 0.06” x 0.03” (metric equivalent is 1.6mm x 0.8mm) but it is always listed in inches by supppliers so you can also search for an 0603 3A 32V ceramic fuse if you can’t find a suitable supplier using the first search method above.
Here’s an image to show where it is located
(click on image to enlarge)
Apologies for not thinking of doing this earlier if it turns out to be the fuse that was the problem
I'm getting too old. ;-(
