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Where can I find the backlight fuse?

Hello everyone, I’m trying to find the backlight fuse on my motherboard. I have a chuwi lapbook pro 14.1 and suddenly the display backlight doesn’t work. But the lcd screen work and a second screen with HDMI work as well. I’m trying to find the fuse in order to test if it’s my LED which doesn’t work or the fuse which is blown… Thanks a lot for your help if someone can find this fuse…. I attached picture of my motherboard.

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antonin.gall

I see that you had not uploaded another side of the mainboard.

what had you checked?

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Yes because the backlight fuse should be around the display port

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where it's written EDP it's the display port

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@antonin.gall ,

Don't know the answer but check if there is voltage is on EDP connector pins 27-30. (Not sure of this but maybe worth a check)

If there is, it may not be a power supply problem as such, it might be a BL_On problem.

With some laptops the backlight power is available all the time to the panel and a signal is sent to the panel to switch it on and off. The actual backlight power supply is not turned on and off on the motherboard

Just so that you're aware of this possibility and don't spend all your time looking for a fuse that may not be the problem.

If you know or can find out the model number of the LCD panel, look for the LCD panel data sheet as this will have the pinout for the cable connection.

If you're lucky the panel make and model number is sometimes found on the back of the panel itself.

Alternatively look for the motherboard schematic by searching online for the "motherboard 'board number' schematic"

Just a thought. Hopefully it doesn't sidetrack you too much if it is not the case with your laptop

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Jayeff, thank you for your answer, unfortunately I can't access to the panel LCD because there are bezel cover and metal cover on the back. Sorry but where is the pin 37-40 ? can you show me on my picture please ? Antonin G

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Hi @antonin.gall,

It should be a DC voltage so set the multimeter to DC Volts (start on the 200V scale - it won't be anywhere near this value at all but it is always safer to start high and then lower the scale to get a more accurate measure) and then connect the meter between an earth point on the motherboard and one of the pins.

Be careful not to "bridge" the meter's test probe across two pins and short them out as you may damage something.

Here’s an image from a different laptop that shows what I mean. (sorry that it is a bit small)

Even though it is a 40 pin connector the principle is the same. LED power (VDD LED) is always there on pins 1, 2 & 3 whilst the backlight on (BKLTON) lead is connected to pin 4.

Again this schematic is not the one for your laptop. It is only to show how it might be wired, so the pin connections might not be the same. It is unfortunate that you can’t find the make and model number of the panel to get the datasheet to make it easier. Did you try searching for the motherboard schematics using the motherboard’s board number at all?

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(click on image to enlarge for better viewing)

If there is no constant LED power on any of the pins as you say there is a problem with the LED power supply on the motherboard.

If there is LED power available then it may be a problem with the backlight on circuit, either on the motherboard or in the panel or the LED power circuit in the panel.

That is of course if it is wired like this and I don’t know if it is or not.

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Hi jayeff,

Thanks for your help, after testing the pins. I’m concluding that there is a voltage of each of them so it’s not a motherboard problem. Maybe it could be the flex screen cable the problem ? because I realize that the hinge fix force on the cable and the cable is a little bit cut.

I cannot find the motherboard schematic of my laptop because chuwi is not a famous brand..

Do you know how I can find the reference of my flex cable 30 pins ? Thanks

por

Hi @antonin.gall ,

Perhaps it isn't a motherboard problem although you still don't know if the backlight on signal is being sent from the motherboard unless perhaps voltage on means turn backlight on which does seem logical

It looks like you may have to access the panel anyway so that you can replace the cable if it is faulty or that you can at least check if the same voltages are getting to the other end of the cable or disconnect the cable at both ends and use an Ohmmeter to test each wire for continuity.

Since you may have to do this perhaps there will be a panel make and model number to be seen unless the panel's cable connector is easily accessible and you don't have to remove the panel to get to it. I can't think of any other way to get the pinout for the more unknown brands.

Either the datasheet for the LCD panel or the schematic for the motherboard and you couldn't find that one. Panel datasheets may be easier as the laptop manufacturers don't make the panels. There are specialist panel manufacturers who make to order and usually they are more well known

With a lot of bezels they are removed from the front by gently lifting from the screen side to unclip them from the lid cover, but again I don't know about your laptop

One step forward ;-)

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Please see the image below. I might have an answer to your question.

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As you said Jayeff, one step forward !! and thanks to you.

Look the picture below of my screen assembly.... It's not a plastic frame but glasses stuff so I will try to use a heater and hopefully remove the screen correctly

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HI @antonin.gall,

It definitely looks like it is stuck on so go slowly and carefully.

Is it also a touchscreen model laptop? If so just hoping the the touchscreen is not fused in with the LCD screen and that you're just removing a glass protective panel.

Good luck

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No it's just a protect glass but not tactile. Yes I'm afraid to broke the lcd ... but I have no choice if I want to take off the flex EDP cable

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hola tengo el mismo problema que el compañero con el mismo lapbook, él puede desmontar la pantalla aplicando calor y con mucho cuidado quitando unas gomas hay unas pequeñas hendiduras para poder meter un desmontador e ir despegando la pantalla de la carcasa, el problema creo que es del cable edp, pero buscando por internet no lo encuentro para reemplazarlo. Pongo una foto del cable y del modelo de pantalla por si me pueden ayudar. Gracias

Google translate:

hello I have the same problem as the companion with the same lapbook, he can disassemble the screen by applying heat and very carefully removing some rubbers there are some small indentations to be able to insert a disassembler and detach the screen from the case, the problem I think is edp cable, but searching the internet I can not find it to replace it. I put a photo of the cable and the screen model in case you can help me. Thank you

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Hi,

If you can't find a replacement cable then if you have an Ohmmeter you can check every wire for continuity between the connectors in the cable

Write down the colour of the wire (if possible) and then make up a pin number count (unless it is marked on the connector) so that you know where every wires goes to.

Once you have a wire that you cannot find the other end to, that may be the problem wire.

You may be able to by-pass the wire with a replacement wire.

If it is a broken wire and not a faulty joint in the connector or in the flex cable then use a pin to pierce the insulation of the wire close to the connector so that it touches the wire and connect the Ohmmeter between the pin and the connector pin (front side) that you think it should be on and see if it is OK. Try this at both ends of the wire.

If the connections seem OK then you can cut the wire and solder in a new one to the ends still connected.

It will be more difficult if the wire is broken in the flex cable or if the wire connection in the connector is broken

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Gracias ire probando por si pudiera repararlo.

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