Question about Panasonic Toughbook CF-51 Notebook

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Panasonic CF-51 backlight intermittent

Voltage to backlight falls when backlight fails. All voltages measured at motherboard connector to backlight power supply read the same (referenced to ground) whether light is on or off. Simulating a lid closure (with magnet by reed switch) and then simulating reopening (remove magnet from reed switch) causes backlight to come back on (each time) for about 10-30 seconds before failure. Reed switch has been isolated and known good.

Question: Is there other circuitry on the motherboard that may cause this problem (even with the voltages measuring the same at the motherboard connector) or is the problem in the backlight power supply located in the monitor frame?



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  • R Shendo May 09, 2009

    screen barely visible when powered on. closed and opening laptop provides normal lcd brightness for a very limited time. overheating?



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1 Answer

The screen flickers when opening laptop.

It's one of two things, either it's the backlight inverter or it's the switch which tells the laptop the lid is closed.

The backlight inverter is what powers the lamps in the back of the screen.They aren't expensive, but a computer shop will probably charge you an arm and a leg to replace.

The switch tells it to turn the backlight off when the lids is down to save power.

If it's the switch, you can disconnect it by following this guide… and… according to that if it thinks the lid it will turn the blue touchpad LED orange to indicate the touchpad is locked.

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Listen carefully to the HDD bay of the CF-51, If the "Clicking" sound is coming from that area then it is possible that the hard drive is failing causing the whole laptop to freeze up.

If that is the case then you're looking at a new or replacement hard drive.


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I found this via

So try that out. I just got a toughbook cf-51 and will try it soon myself. Mine came with an XP reg code so maybe that can run from a virtual machine inside of linux.
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The hard drive caddy is "the catch", for certain.
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There's one on ebay right now ! check it out fast.

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Your best bet is to probably just have any important files from the laptop extracted by a repair shop and then selling the computer "As-IS" on ebay. Or you could try another local repair shop to take a look at it. I wouldn't pay any money for a diagnostics since it would take most techs about 5-10 minutes to confirm what I just typed.

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