Toshiba Qosmio Wierd Backlight Issue

[jft135]

I replaced a bad LCD cable (no image on screen whatsoever) in this Toshiba QOSMIO X505-Q880 and at first the screen would turn on for 10 seconds or so then go dark. Now the backlight never comes on. I've tried 2 known good screens and 2 different inverters just in case my vendor sent me a bad one. I can't find anything online about an onboard fuse anywhere. I'm at the end of my rope, but thought I'd ask on here before I wrote it off. Does anyone have any ideas?

 

[Skillachi]

It could be a bad motherboard or a damage graphics chip on the motherboard

 

[jft135]

It could be a bad motherboard or a damage graphics chip on the motherboard

An external display works great, so that would (usually) rule out a MB or GPU issue. I can tell that the on-board display works too, but there is just no backlight. My next step at this point is to try a little percussive maintenance.

 

[smashedbotatos]

Just because an external monitor works, doesn't rule out a problematic gpu or mb. If you have tried with known good cables, screens, and inverters. I would suggest the gpu or mb is problematic. It maybe a simple bad low level component between the gpu and the LCD output.

 

[jft135]

Just because an external monitor works, doesn't rule out a problematic gpu or mb. If you have tried with known good cables, screens, and inverters. I would suggest the gpu or mb is problematic. It maybe a simple bad low level component between the gpu and the LCD output.

That's what I'm afraid of. I just wanted to make sure I'm not missing anything here. It is a really high end laptop and I hate to tell the customer that it is toast.

 

[River Valley Computer]

You might check the MOBO for a blown fuse. Harder than ever to find but once you do just use an ohmmeter to check it. Typically Toshiba uses green fuses about 1/4" square.

 

[jft135]

You might check the MOBO for a blown fuse. Harder than ever to find but once you do just use an ohmmeter to check it. Typically Toshiba uses green fuses about 1/4" square.

I've seen the fuses before, but usually I can find a picture that tells me roughly where to look. I can't find anything about a fuse on this one, and I'm hesitant to strip it back down and look for it manually when I've already lost so much time on this.

 

[JustInspired]

I replaced a bad LCD cable (no image on screen whatsoever) in this Toshiba QOSMIO X505-Q880 and at first the screen would turn on for 10 seconds or so then go dark. Now the backlight never comes on. I've tried 2 known good screens and 2 different inverters just in case my vendor sent me a bad one. I can't find anything online about an onboard fuse anywhere. I'm at the end of my rope, but thought I'd ask on here before I wrote it off. Does anyone have any ideas?

So is there an image on the screen? Just no backlight?
Possible bad (new) cable?
Trapped or pinched cable?
Lid switch problem like a wayward magnet?

 

[jft135]

So is there an image on the screen? Just no backlight?
Possible bad (new) cable?
Trapped or pinched cable?
Lid switch problem like a wayward magnet?

Sorry it wasn't clear, but yes, after I replaced the cable I'm now getting an image with no backlight.