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The back light on my Presario x1050 laptop did not fire up when I turned on today. Prior to this there had been no display problem whatsoever, specifally no flickering, dimming or red tinge.

I have taken the machine apart and wiggled the video connector cable but this produced no effect.

When powered on I can see a very dim image which suggests the LCD is otherwise healthy. If I plug in an external monitor, it works fine during boot up but as soon as windows loads, the picture goes and the monitor turns itself off. This leads me to suppose the video card is OK but there is probably a windows issue preventing using the external monitor. ( I have pressed the function key to allow the external monitor but this does nothing. )

My Question: Do you think this is more likely to be a simple burned out backlight bulb or do you think it is the inverter board? I can get these off ebay but I am not sure which to try first.

Any suggestions would be very much appreciated!

Thanks ..... Nick :)

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Dani AI

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Short, practical diagnostic path and repair order for this kind of Presario lamp/inverter fault. This ties together 's and 's observations and gives safe, actionable steps to separate an OS/driver problem from a hardware failure and then to isolate inverter vs CCFL lamp.

Start by separating software from hardware:

  • Boot to BIOS/POST and then to Safe Mode or a Linux live USB. If the external monitor stays active with generic drivers or outside of Windows, fix the video driver or the vendor "Fn" hotkey utility first (these control the LCD/external switching).
  • If the external goes dark even before the OS loads, treat it as a hardware fault.

Hardware checks and safe handling:

  • Remove the display bezel and visually inspect the inverter board for burned marks, bulging capacitors, or cracked solder. Disconnect battery and AC before disassembly. When you must measure, reconnect AC only while the unit is open and be aware the inverter output is high voltage — do not touch the inverter high-voltage side.
  • A low-risk confirmation is swapping in a known-good donor inverter (cheap and fast). If a donor inverter restores the backlight, replace the inverter. If not, the CCFL lamp (the long fluorescent tube behind the LCD) or its connectors are the likely cause.

Repair order and part tips:

  • Practically, technicians try the inverter first because it is the easier, lower-cost swap. If you replace the tube, use the exact LCD panel part number printed on the back of the panel so the lamp length/connector match. CCFL replacement is delicate; consider a shop if not comfortable with fragile glass and high‑voltage circuits.
Member Avatar for golar

Probabilities?
I've got a similar problem on a 3 yr old Toshiba. Image is there, just dark. External monitor works. From what I've researched, it is either my backlight bulb (CFCL), the inverter, or the flat cable. My system display was flickering for a couple days, then flickered severely to complete black (without moving the display lid). Due to that mode of failure, I'm going to try the Lamp replacement first.

Good luck.

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