Member Avatar for SimonTB473

Hi all,

Here's a strange one - just replaced a screen backlight inverter on a toshiba satellite U-400. All works fine. Then it becomes intermittent.

When I close the laptop lid (Laptop goes into hibernate) and open it again, the screen invertor won't work - the unit boots up and the screen is there (if you shine a flashlight onto it - you can see the desktop).

So, I shutdown the laptop, re-boot and put inot sleep then hibernate, then sleep etc. and all is fine

Then I shut the lid, wait for it to hibernate and open the lid - no screen backlight

Any ideas ?
Screen/backlight?
Invertor ?
lid switch ?

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Dani AI

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Quick, practical follow-up for (and thanks to for flagging the hibernate/driver angle). The symptom you describe (image visible with a flashlight, backlight fails after resume, inverter recently replaced) narrows the likely causes to three areas: the hinge/display cable or connectors, the power/ACPI resume sequence (drivers/OS), or a faulty/incompatible inverter or panel. Work through the cheaper, lower-risk checks first to isolate hardware vs software.

  • Verify panel type and connectors: confirm whether the U400 uses a CCFL (needs an inverter) or an LED panel (no inverter). If the part you fitted does not match the panel type the symptom can be intermittent.
  • Wiggle/reseat test: with power off, remove the bezel enough to access the display cable and inverter connector. Reseat both ends, inspect for bent pins, and look for frayed wires at the hinge. Reassemble and open/close the lid slowly while watching for the backlight to flicker. If movement changes the symptom, the hinge cable is the usual culprit.
  • Software/ACPI checks: temporarily set "When I close the lid" to "Do nothing" and test manual hibernate/resume. Disable hybrid-sleep/fast-startup (if present), and try a clean reinstall of the video driver or a driver rollback. After resume, try the brightness keys; some drivers resume with brightness set to minimum.
  • Quick isolation: connect an external monitor and resume from hibernate. If the external display is normal, the GPU and OS resume path are likely OK and the problem is local to the LVDS/eDP path, inverter, or panel.

Safety note: inverters and CCFL backlights carry high voltage — do not probe the inverter outputs unless experienced. If reseating and simple driver changes do not fix it, the most common repair after intermittent resume failures is a damaged display cable or a faulty panel; replacing the whole LCD assembly is often faster and more reliable than repeated inverter swaps.

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Member Avatar for rubberman

It sounds like the system isn't restarting the backlight when coming out of hibernation. Did you talk with the techs? I'm sure there is some connection that was either not done, or not done properly that has to be used to trigger restarting the backlight. Since it works if you shut down the system and restart it, then it may be a hibernate or driver problem. I'm just guessing here since I haven't seen this problem myself.

Last question: did you replace the backlight yourself, or had it done by some service?

Member Avatar for SimonTB473

Hi rubberman,

Thanks for the input.

I can't see a driver error on the event logs and yesterday after I wrote the post, the backlight didn't work at all, no matter how I shutdown/re-booted.

I replaced the inverter myself as this was the original issue. I haven't yet looked at the backlight as its part of the screen and dont want to buy one of those just yet !! might just be worth telling my customer to get a new laptop !!

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