Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Laptops, Portable, and Mobile Devices
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 04-17-2017, 10:38 AM   #1
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Lenovo Y50-70 (not touch) - Screen LED Backlight

Hi all,

I need a little help with my second Lenovo y50. Board schematic is attached.

Little explanation, the 40 pin connector for the LCD was broken, I made the replacement and it looks fine. I can see the screen showing some images.

Problem here is that the screen backlight doesn't turn on (tried also the FN + ...). Screen is working fine on my other y50 laptop (cable also).

Could you help me to identify what is wrong on the board? I think about something wrong with pin 28 of the LCD connector but that it...

Thanks a lot !
Attached Files
File Type: pdf compal_la-b111p_r1.0_schematics.pdf (1.94 MB, 160 views)
Kashi1712 is offline   Reply With Quote
Old 04-17-2017, 11:29 AM   #2
piernov
Moderator
 
Join Date: Jan 2016
City & State: Valbonne, 06
My Country: France
I'm a: Knowledge Seeker
Posts: 1,670
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Please post a picture of the area you worked on.
Also, what voltage do you get on pin 28, 29 and 40 of LCD connector?
__________________
OpenBoardview http://openboardview.org | IRC #openboardview@irc.freenode.net
piernov is offline   Reply With Quote
Old 04-17-2017, 02:14 PM   #3
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Hello Piernov,

Thanks for the answer, here is the picture.

Regarding voltage, i get 0V for the 3 pins (28 -29 -40)

Thanks !
Attached Images
File Type: jpg IMG_20170417_205821.jpg (97.8 KB, 87 views)
Kashi1712 is offline   Reply With Quote
Old 04-17-2017, 03:26 PM   #4
rookieme
Badcaps Veteran
 
Join Date: Oct 2014
City & State: Athens
My Country: Greece
I'm a: Knowledge Seeker
Posts: 204
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

There you should have 19V in order to get backlight.
Check R375 and measure voltage at both sides at R375.
R375 is 0 ohms and acts as a fuse.
If it is burned no voltage could pass through to drive the backlight.
rookieme is offline   Reply With Quote
Old 04-17-2017, 03:36 PM   #5
piernov
Moderator
 
Join Date: Jan 2016
City & State: Valbonne, 06
My Country: France
I'm a: Knowledge Seeker
Posts: 1,670
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Not so pretty but it should do the job. Not sure about the 4th and 5th pins from the left though.

Could you mesure all the voltages on PU1203 pins?
piernov is offline   Reply With Quote
Old 04-17-2017, 03:55 PM   #6
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

The 4th and the 5th from the left, there was a scratch, I verified, and both pin join to the ground, so it should be fine.

To solder the connector, I've used my smd rework station with soldering paste, as this is really small, it is really difficult to make it really clean.

I'll measure voltage right now ! Thanks !
Kashi1712 is offline   Reply With Quote
Old 04-17-2017, 04:14 PM   #7
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Is that normal that there is no chip on the pu1203? I will do measures tomorrow as it is quite difficult to access (under the heatsink)
Kashi1712 is offline   Reply With Quote
Old 04-17-2017, 04:23 PM   #8
rookieme
Badcaps Veteran
 
Join Date: Oct 2014
City & State: Athens
My Country: Greece
I'm a: Knowledge Seeker
Posts: 204
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

yes it's normal, you get 19V via R375, R205 doesn't exist [it has @ sign] and schematic has is as it's an option but not used
[pu1203 is a boost converter for 12V]
rookieme is offline   Reply With Quote
Old 04-18-2017, 12:51 AM   #9
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Ok, so the pu1203 has 12 pins

1 - 0v
2 - 0v
3 - 0v
4 - 5.17v
5 - 0v
6 - 0v
7 - 0v
8 - 0v
9 - 0v
10 - 0v
11 - 0v
12 - 0v

This 5v is strange.. sometimes it drops to 3.5v and then go back to 5.17v...
Kashi1712 is offline   Reply With Quote
Old 04-18-2017, 02:29 AM   #10
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Quote:
Originally Posted by Kashi1712 View Post
Ok, so the pu1203 has 12 pins

1 - 0v
2 - 0v
3 - 0v
4 - 5.17v
5 - 0v
6 - 0v
7 - 0v
8 - 0v
9 - 0v
10 - 0v
11 - 0v
12 - 0v

This 5v is strange.. sometimes it drops to 3.5v and then go back to 5.17v...
From the schematic, I think pins are not really the same... I guess that the 4th pin is actually pin 8 (so the 5v input is correct)
Kashi1712 is offline   Reply With Quote
Old 04-18-2017, 04:46 AM   #11
rookieme
Badcaps Veteran
 
Join Date: Oct 2014
City & State: Athens
My Country: Greece
I'm a: Knowledge Seeker
Posts: 204
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

have you measured voltage at R375 ?
rookieme is offline   Reply With Quote
Old 04-18-2017, 04:48 AM   #12
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

I've tried to find that one, but don't know where it is located on the board. Any clue?
Kashi1712 is offline   Reply With Quote
Old 04-18-2017, 05:06 AM   #13
rookieme
Badcaps Veteran
 
Join Date: Oct 2014
City & State: Athens
My Country: Greece
I'm a: Knowledge Seeker
Posts: 204
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

you can follow the trace from the pins of the lvds if that is possible
a boardview can help you to find it at the moment if you can find one for this board
rookieme is offline   Reply With Quote
Old 04-18-2017, 06:11 AM   #14
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Didn't find the boardview, I will check if it is visible or not.... Looks difficult
Kashi1712 is offline   Reply With Quote
Old 04-18-2017, 06:16 AM   #15
rookieme
Badcaps Veteran
 
Join Date: Oct 2014
City & State: Athens
My Country: Greece
I'm a: Knowledge Seeker
Posts: 204
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Last option is to run a cable from 19V [B+ or CPU_B+ or anything that suits for you] and solder it at lvds pins 38-40.
A better option is to use a zero ohm resistor as a fuse or a use of 2,5- 3A between the cable and the pins.
With the 19V you'll get your backlight.

Last edited by rookieme; 04-18-2017 at 06:18 AM..
rookieme is offline   Reply With Quote
Old 04-18-2017, 07:51 AM   #16
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

the 19v wire is not too risky? I can see on the schematic that there a some resistor/capa.

I would not take the risk to damage the LCD that is working... But if I can rewire 38-40 pin in another way that is not risky, i'm ok with that.
Kashi1712 is offline   Reply With Quote
Old 04-18-2017, 10:39 AM   #17
piernov
Moderator
 
Join Date: Jan 2016
City & State: Valbonne, 06
My Country: France
I'm a: Knowledge Seeker
Posts: 1,670
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

R375 should be the component circled in red in the following picture. Maybe yours is blown too.

(Source: http://www.elektroda.pl/rtvforum/topic3228153.html )
Attached Images
File Type: jpg 4156723500_1469006658.jpg (1.92 MB, 82 views)
piernov is offline   Reply With Quote
Old 04-18-2017, 10:47 AM   #18
rookieme
Badcaps Veteran
 
Join Date: Oct 2014
City & State: Athens
My Country: Greece
I'm a: Knowledge Seeker
Posts: 204
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

nice photo, this should do the job
rookieme is offline   Reply With Quote
Old 04-18-2017, 12:08 PM   #19
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Ok from the point next to pu1101, I get 7.8v. on the other one, 1.30v

I've tried to put 19v from the 16th pin on the pu1101 but laptop shuts down immediately. Still doesn't work
Kashi1712 is offline   Reply With Quote
Old 04-18-2017, 01:03 PM   #20
Kashi1712
Member
 
Join Date: Jan 2017
City & State: Brussels
My Country: Belgium
I'm a: Knowledge Seeker
Posts: 39
Default Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

I will post a picture of it, mine looks just fine
Kashi1712 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2019
Powered by vBulletin ®
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 10:26 PM.
Did you find this forum helpful?