Member Avatar for deegiee

I have a Toshiba P100 with a faded LCD screen, I can connect it to an external monitor and everything works fine on the external monitor, but I can barely see anything on the laptop screen. I replaced the inverter first but that didnt help, so I replaced the LCD convinced that that was the problem, but still the same problem persist - works on the external monitor, faded on the new LCD screen. Can anyone help?
thanks
regards
don

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  • Latest Post Latest Post by kaninelupus

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Good points from and useful context from — focus the next troubleshooting on the display backlight and its power path rather than the video output. The following checklist is model‑agnostic and meant to isolate lamp, inverter, cable, or motherboard faults so replacement parts are used only where they’re actually needed.

  • Flashlight test: with the laptop powered on, shine a bright flashlight at the screen from a sharp angle. If a faint image is visible, the panel is receiving video but the backlight is not lit — that narrows the fault to backlight/inverter/power wiring.
  • Physical inspection and reseat: power down, remove battery/AC, open the bezel and inspect the LVDS/backlight cable where it passes the hinge. Look for pin damage, crimps or broken insulation and reseat both panel and motherboard connectors carefully.
  • Confirm part compatibility: check the sticker/part number on the replacement panel and confirm whether it uses CCFL or LED backlight. Incompatible inverters or wrong-panel types will never light the lamp even if mechanically identical.
  • Inverter power check (if comfortable using a DMM): with the system on, confirm the inverter receives its DC supply and an “enable/on” signal. If neither is present the problem is upstream (cable or motherboard); if present but the lamp stays dark the inverter or lamp inside the panel is bad.
  • Swap with a known‑good item: the quickest definitive test is to plug a known-good inverter or tested panel into the system. If bench‑tested parts are not available, source “tested” replacements from reputable suppliers.

Safety note: avoid probing connectors or working powered with exposed boards unless experienced. If the inverter shows no input power after these checks, a repair shop can trace the board fuse/enable line; if the inverter is powered but won’t light a tested lamp, replace the panel or inverter with a verified part.

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Member Avatar for kaninelupus

Check you power options - have the ability to set the screen brightness for plugged in and on battery... may need resetting

Alternatively, most notebooks have hotkeys to adjust screen brightness.

Sometimes these settings are universal (ie, for both inbuilt and external monitors), but often they are not

Member Avatar for deegiee

In the power options settings, display is set to never turn off and brightness is set to maximum.

Member Avatar for kaninelupus

Have a look , as may be a back-light issue (had assumed back-light was actually part of monitor, so never thought to suggest).

Let us know if this helps, as may well be useful to others.

EDIT: Found guide, which is same topic but specific to Toshiba notebooks, so might be more helpful :)

Member Avatar for deegiee

Thanks kaninelupus, thats an excellent website. I dont think its the backlight as the LCD screen is new, I have a feeling my replacement inverter is faulty too. I got it off ebay.

Member Avatar for kaninelupus

Thanks kaninelupus, thats an excellent website. I dont think its the backlight as the LCD screen is new, I have a feeling my replacement inverter is faulty too. I got it off ebay.

LOL. I by a lot of IT stuff online, but almost NEVER from eBay... usually from reputable on-line merchants. Saves a world of grief. Well, you live and learn :-/

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