need help with my Toshiba l755 backlight

[new]

i have a problem with my Toshiba satellite l755 . there's a very dark faint light that i can hardly see the image . when i plugged it to external monitor it is working fine . replaced the lcd cable and replaced the screen itself . still the same problem .. can someone please tell me where could be the problem . i have tested the power and the PF2 fuse they are ok . where is other fuses i can check . i appreciate the help .

p:s it was working fine till it bricked due too bad flash rom then i gave it to someone to reflash the bios . he brought it back working with no backlight .

can reflashing the bios cause this issue ?does the bios has anything to do with the led backlight being so dark .
thanks

[ktmmotocross]

Re: need help with my Toshiba l755 backlight

maybe. u better try flashing it again

[Agent24]

Re: need help with my Toshiba l755 backlight

Never heard of bad BIOS stopping backlights but I suppose it's possible depending on how it all works.

Unless he screwed something when he had the thing apart.

[siddiq]

Re: need help with my Toshiba l755 backlight

You need to specify your motherboard model number so I can look at a schematic and help you out.

[new]

Re: need help with my Toshiba l755 backlight

i have read online that EC bios control part of the backlight so not sure if is it possible flashing the wrong EC bios can cause the backlight to back out .as i said there is display only you will notice it if you look very closer with a light on .you will notice a very faint image .but still work just fine on external monitor

[new]

Re: need help with my Toshiba l755 backlight

just my question here , does the EC has anything to do with the backlight ??? i read some post from someone here . he had the same issue as me and a guy told him you either have a faulty dim switch or dead EC ???? so i believe if the EC totally dead the laptop won't boot at all . right ?

[khaahk]

Re: need help with my Toshiba l755 backlight

EC usually has output that drives the backlight enable circuit. Sometimes just this output of ec is dead, then the laptop will work fine otherwise.
If the schematics is correct, then DISPON signal is not driven by EC in your case

[Agent24]

Re: need help with my Toshiba l755 backlight

I forgot about the EC. That makes sense, it could affect it

[new]

Re: need help with my Toshiba l755 backlight

so reprogramming the EC can fix that issue ? or the chip needs to be replaced ?

[Agent24]

Re: need help with my Toshiba l755 backlight

It would need to be reprogrammed, just like main BIOS. Since you had a bad flash that is possibly the problem.

[new]

Re: need help with my Toshiba l755 backlight

this board is intel not AMD .. the guy who programmed the bios told me he programmed U29 the main bios and he programmed U10 the EC bios ..... just wonder maybe he programmed the wrong chip

[Agent24]

Re: need help with my Toshiba l755 backlight

I don't think there are any other chips to program.

[new]

Re: need help with my Toshiba l755 backlight

so the EC and the main bios is only one chip or 2 separate chips ?

[Agent24]

Re: need help with my Toshiba l755 backlight

Physically separate. That's why you have two different reference designators, U29 and U10. You should be able to find them on the schematic.

[new]

Re: need help with my Toshiba l755 backlight

so u10 and u29 is the right chips ... there are lots of chips on this board looks like the bios ...

[new]

Re: need help with my Toshiba l755 backlight

can someone provide me with the right U10 and U29 rom files i can pass them to him to reprogram he might got the wrong files . i appreciate all the help

[new]

Re: need help with my Toshiba l755 backlight

the motherboard is intel not AMD

[new]

Re: need help with my Toshiba l755 backlight

also when the backlight very dim (very dark)you can't see it till you put a flash light on the screen . is that a sign of bad EC ????

[Agent24]

Re: need help with my Toshiba l755 backlight

also when the backlight very dim (very dark)you can't see it till you put a flash light on the screen . is that a sign of bad EC ????

Just means the backlight is not on. Doesn't tell anything of why. There are many things that could cause the backlight to fail.

EC was suggested as he reprogrammed it, if it does indeed control the backlight it may be wrongly controlling it if it has wrong or corrupt firmware. But I can't say for sure it is the problem.

[new]

Re: need help with my Toshiba l755 backlight

can someone please provide me with the right EC firmware to try with . i'll give it to him to reprogram the EC again . hopefully this will fix the issue