Asus X453MA Rev 2.0 Backlight and fan

[Christian0734]

Hello,
I brought an Asus X453MA into the workshop, its owner tells me that it doesn't work on battery despite having replaced it with a new one and that it's making noise. I diagnose and find, firstly, that the fan is constantly running at full speed. Secondly, that the computer works on battery but there's no backlight when the charger is not connected. I look at the screen connector because I see that the adhesive is not holding. I observe that there probably was a short circuit. I isolated everything with hot glue and reassembled it, I don't think it needs to be replaced. The BIOS is in its latest version, everything works normally, the PC doesn't overheat, just the fan running at full speed and the backlight that turns off when the charger is unplugged. The display itself, it works. I inspected the motherboard under a microscope, I saw nothing abnormal, I did not identify any short circuit. Do you have any ideas?

[mcplslg123]

Try replacing the coil marked "100" on the screen card. thats the solution for backlit issue on many asus platforms. Weird but works.

[Christian0734]

Try replacing the coil marked "100" on the screen card. thats the solution for backlit issue on many asus platforms. Weird but works.

Thank you for this response. Point to consider:

the screen backlight works on mains power. It also works when an external monitor is connected to the HDMI port in battery mode. The battery is new, and the phenomenon occurs with both the old and new batteries. The computer and display work normally on battery, it's only the backlight in battery mode that does not work. In this case, can we suspect a problem with the inverter or a component on the screen's board?

[mcplslg123]

This trick works exactly in the scenario you described. backlit works in adapter mode but flicker/not work in battery mode. At the outset i said its weird but works for many people.

[Christian0734]

This trick works exactly in the scenario you described. backlit works in adapter mode but flicker/not work in battery mode. At the outset i said its weird but works for many people.

Ok, thank you for the information, I will dismantle the screen.

[Christian0734]

This trick works exactly in the scenario you described. backlit works in adapter mode but flicker/not work in battery mode. At the outset i said its weird but works for many people.

I disassembled the screen, I found three coils with the number 100 (see photo), none of them are cut...

For the fan, however, it's fixed, it was the NCT7717U thermal sensor that must have acted as a fuse.

[mcplslg123]

The coils are never broken or cut in this scenario. the smaller coil marked 100 is to be replaced near the backlit controller.

[Christian0734]

The coils are never broken or cut in this scenario. the smaller coil marked 100 is to be replaced near the backlit controller.

Is there an explanation for this? I am surprised. The photo is misleading, the two coils circled in red in the photo are exactly identical and have the same resistance to current flow 0.2 Ω.

[mon2]

Post the full top side markings of the nearby backlight IC.

[Christian0734]

Post the full top side markings of the nearby backlight IC.

The IC on the first photo between the two coils: U2 CM512
The other one completely to the left next to the largest coil: U5 CM509A

[mon2]

The following website (translated) states the cm509A can be replaced with a Richtek:

https://monitor.net.ru/forum/threads/679804/

[Christian0734]

The following website (translated) states the cm509A can be replaced with a Richtek:

https://monitor.net.ru/forum/threads/679804/

Thank you for the message. I do not plan to change the integrated circuit. It was only a matter of coils in the message from "mcplslg123". However, do you think that if the backlight does not work on battery but does work on mains power, could it be due to U5?

[mon2]

To me, the coil does not sound like the solution since it is only a piece of wire. Respectively, the suspect is more likely the switching regulator and the quality of the design. Never heard of CMI semiconductor before this thread. My bet would be more on the actual backlight led IC and that should fire up every time and not be flaky with the selection of the inductor onboard nor the power path. Just my 2 bits.

[mcplslg123]

I'll still bet for the coil marked "100". Search for threads within this forum about asus backlit and see for yourself it worked for so many people. I had success with this method on 2 times in asus.

[Christian0734]

I'll still bet for the coil marked "100". Search for threads within this forum about asus backlit and see for yourself it worked for so many people. I had success with this method on 2 times in asus.

Yes, indeed, I have browsed through the forum and found what you were talking about. However, I can't seem to identify which coil is being referred to. I have three where it is marked "100"

[mon2]

These parts are very inexpensive. Replace all 3 of them. Also consider to source the replacement component from Richtek if available to you from Aliexpress or similar. Suggest to measure the pad to pad spacing of the inductor pad / width of the inductors for the proper replacements. You will need to flux and apply proper heat with low air pressure to remove each such inductor.

[Christian0734]

These parts are very inexpensive. Replace all 3 of them. Also consider to source the replacement component from Richtek if available to you from Aliexpress or similar. Suggest to measure the pad to pad spacing of the inductor pad / width of the inductors for the proper replacements. You will need to flux and apply proper heat with low air pressure to remove each such inductor.

It's not so much about the cost of the component, but the shipping fees and availability. I have a few broken screens, so I might just find what I'm looking for...
Do you think these two coils are equivalent?

[mon2]

Yes. Just be sure to align the bottom side solder tabs / bar onto the PCB in the same direction as the original.

[Christian0734]

Yes. Just be sure to align the bottom side solder tabs / bar onto the PCB in the same direction as the original.

Wow! Incredible, it works, I only replaced the one I took a photo of and I got the Backlight working on battery! Sincerely, thank you mcplslg123 et lundi2

[mcplslg123]

I told you right from the beginning its weird but works.