Toshiba Satellite LED screen no backlight

[mangkook]

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.

you mean that I have wrong pin (from motherboard) connect to the led (ribbon)? It does says "Toshiba" on one of the socket so put it there obviously. on second thought I think I did mistakenly put it on HP621 socket once but no backlight either.


image upload

@spleenharvester


I will look into that matter and gave feedback soon.

do you mean I need to take the readings with the motherboard power on?

[mangkook]

Re: Toshiba Satellite LED screen no backlight

so I've been busy these 2 days, sorry no report or test yet.

could it be that I mistakenly slip the ribbon upside down to the LED (in my first try) that burn something?

[spidey]

Re: Toshiba Satellite LED screen no backlight

it may say "toshiba" on the board, but dont trust that mark. Compare it yourself, it will be done.

[mangkook]

Re: Toshiba Satellite LED screen no backlight

I will make some drawing of the wiring tonight. thats the only way I can see it straight.. BTW, what would cause the OLD ccfl backlight not lighting up after testing with this new LED? that actually bothers me a lot, like something burn in mobo? or some gpu related?

[spidey]

Re: Toshiba Satellite LED screen no backlight

just measure the connector pins which connected to converter in the photo. Then check lcd panel schematic and change the order of the pins.

[mangkook]

Re: Toshiba Satellite LED screen no backlight

can I use this as reference?

[spleenharvester]

Re: Toshiba Satellite LED screen no backlight

Oddly enough, a lot of those LED converter things have an "L505" or "L500" socket, but not that one. Eitherway I don't think that's your problem now. Also HP621 is in the same socket on a different board

I do have a semi working L500 board I can take some readings off near the LCD connector if you need.

[spidey]

Re: Toshiba Satellite LED screen no backlight

acording to pdf file you posted :

31 GND LCM Ground (LED Backlight Ground)
32 GND LCM Ground (LED Backlight Ground)
33 GND LCM Ground (LED Backlight Ground)
34 NC No Connection.
35 PWM System PWM Signal input for dimming
36 LED_EN LED Backlight On/Off
37 NC No Connection
38 VLED LED Backlight Power (7V-21V)
39 VLED LED Backlight Power (7V-21V)
40 VLED LED Backlight Power (7V-21V)

[DarthChrisB]

Re: Toshiba Satellite LED screen no backlight

Hi
I have a Toshiba Satellite P100 with the same problem. I've already replaced the backlight bulb and inverter with no result. After testing the pins on the inverter when powered on i found out that pin 2 has 12 volts but pin 1 has 0 volts. While supplying 9 volts to pin 1 with a battery the light turns on.

So my question is how can I track down to the root of the error. I couldn't find any fuses around the lcd connector and the few other fuses that I found are working.

[fddizon]

Re: Toshiba Satellite LED screen no backlight

Hi
I have a Toshiba Satellite P100 with the same problem. I've already replaced the backlight bulb and inverter with no result. After testing the pins on the inverter when powered on i found out that pin 2 has 12 volts but pin 1 has 0 volts. While supplying 9 volts to pin 1 with a battery the light turns on.

So my question is how can I track down to the root of the error. I couldn't find any fuses around the lcd connector and the few other fuses that I found are working.

trace it back to mobo

[DarthChrisB]

Re: Toshiba Satellite LED screen no backlight

trace it back to mobo

I know it's the mobo, that's basically what I concluded in my first post. My Question is how can I find the component that needs to be replaced?

[firefoxie]

Re: Toshiba Satellite LED screen no backlight

Hi, I just wanted to say: thank you. This thread set me off in the right way. And I just got an LCD panel backlight back to life in a mysterious way. I hope to share my experience here.

First, thanks for this thread. I have a faulty Toshiba L500-128 with la-4981p mother board that has no backlight after a water damage incident (glass of drinking water). Ordered a new inverter, still nothing.

I've measured +3.3v on pin 40 (BKOFF), +19 on 33-35-37-39, 0v on 9 (DAC_BRIG), but only 0.1v on pin 11 (INVT_PWM). Now I read somewhere (please correct me if wrong) that DAC_BRIG can be zero, but INVT_PWM should be between 3.0v-3.6v (analog reading of PWM signal).

OK, well the laptop is already a write-off. So I shortcut BKOFF and DAC_BRIG to get +3.3v on INVT_PWM, to have at least some sort of 50% brightness, which is better than no backlight at all. This worked to expectations.

Now comes the weird part. While probing I actually touched this INVT_PWM quite some times with the +3.3v from BKOFF, and at some point it just stayed on all by itself (!?). My plans to solder them was not necessary.

My theory here is that -maybe, just maybe- , the chip that sends the INVT_PWM needed a little help "starting up", or getting "unstuck" after the short circuit of the water damage.

Allright. Some pictures included. Thanks again.
Laptop is up for an hour so far and still works.

[techman1025]

Re: Toshiba Satellite LED screen no backlight

Hi you must have left the battery in when replacing screen that's what's happen if all voltage is present then you killed the display cable you could test with ohm meter pin to pin end to end all resistance should be the same or close if any missing or way off replace it and you will be sent to go.
Techman1025

[rickybucalan]

Re: Toshiba Satellite LED screen no backlight

i did this kind of trouble you have now. try to find my thread lenovo g450 no backlight on led screen.i t might help you.

[eniac22]

Re: Toshiba Satellite LED screen no backlight

where can buy the motherboard LVDS connector?

[xquang77]

Re: Toshiba Satellite LED screen no backlight

laptop toshiba Satellite L550-10N, when I turn power is Fan CPU run 30s and then off, but power light still lamp. someone help me please ! Thank You !

[xquang77]

Re: Toshiba Satellite LED screen no backlight

aptop toshiba Satellite L550-10N ( KSWAA LA-4981P ), when I turn power is Fan CPU run 30s and then off, but power light still lamp. someone help me please ! Thank You !

[passete]

Re: Toshiba Satellite LED screen no backlight

aptop toshiba Satellite L550-10N ( KSWAA LA-4981P ), when I turn power is Fan CPU run 30s and then off, but power light still lamp. someone help me please ! Thank You !

Check GPU, need maybe a reball or a reflow.