Member Avatar for Bob423

Now this is really weird. I have an IBM R40 laptop, several years old. All of a sudden (today), the screen backlighting goes off after 18 seconds. I can get it back on by moving the screen on its hinges (fore and aft), it comes back on for 18 more seconds and then goes off again. The screen is still active (I can see the data on the screen in a bright light), the laptop otherwise works, it's not in hibernation or in screen saver mode).

Today I timed it several times. The backlighting cuts out after exactly 18 seconds but everything else is working! It's just like clockwork: move the screen, it's on for 18 seconds, then the backlight goes off! The laptop otherwise works fine. Move the screen again, and it's on for another 18 seconds then the backlighting goes off again?!?!

Does anyone have any ideas of what could be the problem?

Thanks, Bob

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Dani AI

Generated

The pattern described — the LCD image still visible in bright light while the backlight reliably cuts out after a short interval and is temporarily restored by moving the lid — is a classic hardware-failure signature rather than an OS or power‑management issue. That behavior most commonly comes from a display-hinge/flex cable or its connector losing reliable contact as the lid is moved; movement temporarily re-establishes the connection.

Practical checks and safe diagnostics:

  • Confirm the panel still shows an image with a strong flashlight when the backlight is off. That separates panel/GPU failure from backlight power loss.
  • Before opening anything, shut down, remove AC and battery. If comfortable with basic disassembly, remove the display bezel to inspect the ribbon/cable where it passes through the hinge and where it plugs into the inverter/motherboard.
  • Look for torn insulation, exposed strands, or crushed insulation at the hinge. Gently reseat the cable at both connectors (LCD and motherboard/inverter), then test while slowly moving the lid to see if the fault reappears.
  • Never probe the inverter while powered — it carries high voltage. If you must test while powered, use extreme caution and nonconductive tools, or leave live testing to a technician.

Repair and next steps:
A hinge-harness/cable replacement is often the fix and is far cheaper than replacing the panel. If a new cable doesn’t cure it, the inverter board or the CCFL backlight (R40 era) may be the next suspects. If unsure, note the exact model/FRU from the service label before ordering parts and consider professional replacement to avoid damaging the panel or connectors. ’s follow-up posts may have added hands‑on tips.

Member Avatar for rkv

will post soon

Member Avatar for Bob423

Well, I got my problem solved by replacing the cable to the LCD (that powers the backlight). Everything works fine now. The backlight, the inverter and the LCD was fine, just the cable was bad. It cost $35 for labor and $60 for parts.

Bob

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