Réparez vos affaires Communauté Boutique

The Lenovo Thinkpad X380 Yoga is a 2 in 1 laptop created by Lenovo as a part of the Thinkpad X series in 2018.

4 questions Voir tout

Options

Where is the backlight fuse?

After changing the keyboard, the LCD backlight stopped working. I think whoever changer the keyboard didn’t disconnect the battery and popped the fuse in the process. I'm thinking of changing it, but I can't find it. I’ve tested continuity in some components of the board, but I didn’t find anything wrong

This is the first time I use this site, so I don’t know if the images are what or where they’re meant to be, so tell me if something’s wrong

Also, if you think the problem is something else, please let me know.

Block Image
Block Image
Block Image
Block Image
Répondre à cette question J'ai le même problème

Cette question est-elle utile ?

Oui Non
Indice 0
1 commentaire

Hello all,

I have a similar problem.

Lenovo T495,

Display renewed

Switched on everything great,

Then display was dark, I think I have killed by trying fuse.

Can someone help me where the display fuse is located?

par

Ajouter un commentaire

1 Réponse

Filtrer par :
Les plus utiles Les plus récentes Les plus ancien(ne)s
Réponse la plus utile

Options

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

Block Image
Block Image

(click on images to enlarge).

Hopefully a start

Update (01/30/2022)

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.

Block Image

(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

Update (03/25/2022)

@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

Block Image

(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. ;-(

Cette réponse est-elle utile ?

Oui Non
Indice 6

8 commentaires:

Oh my, thats a lot of information. I'm going to try everything you told me tomorrow (it's late where I live), but thank you very, very much anyway, I couldn't find answers anywhere else (this is my first reply I got from like 10 forums), even if this doesn't work I'm hugely grateful.

I'll keep you updated

par

@donfurlan

Further bit of info for you is that the lid sensor is usually found in the Power On button board, so if power is at the eDP connector check the lid sensor circuit next.

Only suggest this as you said that the keyboard was replaced and maybe the power button board connection was affected. Just a thought.

par

Hello!, I think I tested everything you told me and I got some information from it, but I'm not sure what to do with it:

eDP Pins 21-22-23 don't have power. Pin 5 of U9* does have power, and what I think is R361 has continuity (the little one on it's side also works). This is shown here: https://imgur.com/a/K4eHF6c

I'm not quite sure how to test the lid sensor circuit, but I did test the continuity between the magnet part and the rest of the board, and it doesn't change no matter if the lid is open or closed, there is always continuity. This is shown here: https://imgur.com/a/ZchTW0F

Do you know how should I proceed? because I'm not really sure. Thank you very, very much in advance

*Changed U6 to U9*

par

@jayeff Hello, Just in case I'll clarify that I posted an update in an answer because the character limit wouldn't let me post a comment

par

@jayeff Hi Jayreff, I'm back. First of all I wanted to apologize for being absent these weeks, I was using my holydays for other projects, but now it's time to return to this malfunctioning device.

To begin with, I want to clarify that I'm not a technician, so I don't know exacly what these numbers mean, but I measured continuity with my multimeter (based in what you told me) and I wrote down the values that I got (I'm not sure what unit these values have, I don't know if they are Ohms or microohms or other unit, it's what the multimeter gives in continuity):

First, the connection betweet Pin 5,6 and 7 of JBTN1:

Without the battery and the lid closed:

- Resistance from pin 5 to 6 of JBTN1= 750 continuous

- Resistance from pin 6 to 7 of JBTN1= 1370-1900 and it cuts instantly

- Resistance from pin 7 to mass= 595 continuous

Without the battery and the lid open:

- Resistance from pin 5 to 6 of JBTN1= 732 continuous

- Resistance from pin 6 to 7 of JBTN1= 1200-1800 and cuts instantly

- Resistance from pin 7 to mass= 595 continuous

With the battery and the lid closed:

- Resistance from pin 5 to 6 of JBTN1= (-1310) continuous

- Resistance from pin 6 to 7 of JBTN1= no continuity

- Resistance from pin 7 to mass= (-1375) continuous

With the battery and the lid open:

- Resistance from pin 5 to 6 of JBTN1= 089 continuous

- Resistance from pin 6 to 7 of JBTN1= 178 continuous

- Resistance from pin 7 to mass= (-1375) continuous

Now, for U9 and pin 25 of the eDP connector:

Without the battery and the lid closed:

- resistance from U9 pin 4 to eDP 25= 500-1500 and quickly cuts

- resistance from U9 pin 5 to eDP 25= 1725 and quicly cuts

without the battery and the lid open:

- resistance from U9 pin 4 to eDP 25= 500-1500 and quickly cuts

- resistance from U9 pin 5 to eDP 25= 1795 continuous

With the battery and lid closed:

- resistance from U9 pin 4 to eDP 25= 100 continuous

- resistance from U9 pin 5 to eDP 25= 249 continuous

With the battery and the lid open:

- resistance from U9 pin 4 to eDP 25= 100 continuous

- resistance from U9 pin 5 to eDP 25= 249 continuous

By the way, the lid switch is magnetic, and it seems to work just fine. Waving a magnets over it changes values.

Also, I couldn’t test the chipset connections, because I literally cannot find the chipset itself. They usually look like small processors but there are none in sight.

So this is the information I have so far, and it makes me suspicious of U9, but I can't confirm it, what do you think?

And finally, do you have any idea what voltage the backlight leds use? So I can test them and make sure that the leds are not just burned.

As always, thank you very, very much for all the help you are giving me. Thanks to you I’m learning a lot about a world that I never thought I would explore.

par

Voir 3 commentaires en plus

Ajouter un commentaire

Ajouter une réponse

Lucio sera éternellement reconnaissant.
Nombre de vues :

Dernières 24 heures : 3

7 derniers jours : 14

30 derniers jours : 50

Total : 2,371