Toshiba Satellite LED screen no backlight

[mangkook]

Hi guys

I have a problem with Toshiba Satellite L500 led / lcd no backlight problem

the chronology is like this:

1. Toshiba Satellite L500, busted LCD, Still have backlight. Only parts of it cracked.

2. Order LCD screen from online, part no: LP156WH1

3. problem with stock lead to replacement with compatible LED screen part no: LP156WH4

4. assembled the LED screen (no inverter obviously) > boot, blank no backlight. image is visible but very faint

5. tested with old LCD + original inverter > boot, also blank no backlight (wierd, used to be OK). image is visible but very faint.

6. tested the vga to external monitor, OK.

Now I've searched the internet and found suggestions that maybe the fuse controlling the power is busted.

Is there anyone with the same experience? please help

1. can it be that the fuse that control the power is busted?

2. Can I fix it?

3. if answer to both question 1&2 is YES, where can I locate this fuse and how to fix it.

if I should post some attachment pic, which part should I capture?

[rievax_60]

Re: Toshiba Satellite LED screen no backlight

The fuse looks like a surface mount resistor, sometimes white or green or black coloured I think and usually marked with a single letter like a "P" to indicate the current rating.
It will feed the 19v adapter supply to a number of adjacent pins on the mainboard connector tied together.
Sometimes when a wrong LVDS cable is used, the control lines to the backlight circuit can be damaged. These control lines usually come from the keyboard controller IC.

[mangkook]

Re: Toshiba Satellite LED screen no backlight

thanks for the quick reply

so I should find this fuse on the motherboard? I already took out the motherboard and still trying to find it using magnifier.

[rievax_60]

Re: Toshiba Satellite LED screen no backlight

thanks for the quick reply

so I should find this fuse on the motherboard? I already took out the motherboard and still trying to find it using magnifier.

Thats right. Often when I dont have a schematic, I look for pins on the mainboard LVDS connector that are tied together and try to trace where the track goes to. When pins are tied together, it is because they are for power rails or ground connections.

[mangkook]

Re: Toshiba Satellite LED screen no backlight

I wonder if the schematic : https://www.badcaps.net/forum/attach...7&d=1373766252 , from older thread: https://www.badcaps.net/forum/showthread.php?t=30076

can be any use?

I'll try to take pic tomorrow. its already too late here in my country and I dont have any camera with me apart from my old phone camera.



update with phone camera, focus on JLVDS part.

[spidey]

Re: Toshiba Satellite LED screen no backlight

find the schematic, check lvds circuit. find Vin(18-19v), on/off(+3v) and brightness(150-200mv to 2-3v). Most probably you dont have vin or on/off signal. trace back this signals and fix the fault.

[mangkook]

Re: Toshiba Satellite LED screen no backlight

the schematic found here: https://www.badcaps.net/forum/attach...7&d=1373766252

are quite similar, its LA-4982P while my board is LA-4981P. perhaps just minor change?

can I use this as reference? I'm very new in this. dont even understand what exactly I'm looking for.

I found many VIN in these pdf schematic but can't decide if they're connected to LVDS.

[alihomee]

Re: Toshiba Satellite LED screen no backlight

you need to test the voltages on inverter one is 18v and other is 3v to turn on the inverter if not present then chech on lcd connector on mother board

[spidey]

Re: Toshiba Satellite LED screen no backlight

they are nearly the same, i have both of them. you can use the schematic.Page 18 of schematic, check for +LCD_INV and, BKOFF#.

[spidey]

Re: Toshiba Satellite LED screen no backlight

if C677, C678,C392 are (or one of them is) not short, and L17 is good too then you should get +18-19v on +LCD_INV. So if BKOFF# is not +3v then it is EC problem. Anyway measure them all, and post back.

[mangkook]

Re: Toshiba Satellite LED screen no backlight

thanks guys

I'm waiting fro my brother who's into electronics to come, for the meantime I'll try to crunch some of the info above and going to find multimeter and learn how to use them

I'll be back.

already spend 100 buck for the LED screen and I'm not going to let this thing die on me!

[spidey]

Re: Toshiba Satellite LED screen no backlight

dont worry, its just a back light. if cant fix the problem, anyway we can make it work.

[speedypro]

Re: Toshiba Satellite LED screen no backlight

Same issue happened to me with my customer's Dell Inspiron M5030. Hope that shine some lights.

[spidey]

Re: Toshiba Satellite LED screen no backlight

for that one, you must open a new thread, with your measurements. Dell m5030 has a known issue, blown fuse near lcd con. on motherboard. check it.

[mangkook]

Re: Toshiba Satellite LED screen no backlight

Ok guys, under my brother guidance,

I can confirm using multimeter that C677, C678,C392 are NOT short

I hope I read it right..


photo sharing sites

[spleenharvester]

Re: Toshiba Satellite LED screen no backlight

Probably isn't this but look top-down into the LVDS connector. Are all the pins straight?

I had this on an L300, and it turned out that because I plugged the connector in at a slight angle, two pins had bent and ended up in the same part of the connector.

[spidey]

Re: Toshiba Satellite LED screen no backlight

would be nice to see inverter side connector, with pin measurments.

[mangkook]

Re: Toshiba Satellite LED screen no backlight

I hope the pic is suffice..


screen shot on a pc

I edit the pic to overlap to show the connector side according to the LVDS socket

also, Ive checked the connector, all of it and cant find anything bend or something wierd.

I post a few pic just to show you guys my current situation







photo storage

[spidey]

Re: Toshiba Satellite LED screen no backlight

ok, you dont have an inverter. it is a led converter. so the problem is wrong connection. just make sure pins located correctly by chaecking led panels circuit schematic. it should work when you find and change.

[spleenharvester]

Re: Toshiba Satellite LED screen no backlight

OP did you get round to taking some DMM measurements on that connector? That all the voltages are there etc?