Backlight issue - a strange one.

[Wessex_Electric_Nutter]

And yes, its weird:

Someone I know off came to me with a problem on their laptop, which naturally, did not work, the computer functions and works properly, but the sreen didn't. The story behind it is they started it up, went away and the computer died (screen went black), which I have been able to reproduce. I've changed the old display for a new one to which the inverter failed as well as I've guessed this is an inverter related problem. When I plugged the old screen back in, it works perfectly, but I can't seem to trace the inverter failure after checking the cables to begin with.

The video controller seems to be ok (as it outputed to another screen via the VGA connection) and as far as diagnostics, this is as far as I can go, I maybe able to source some other tools (multimeters, osciliscopes, etc), to determine the problem, but I just want some heads to be banged together to see if I've overlooked something. Has anyone else got any suggestions?

 

[clam1952]

And yes, its weird:

Someone I know off came to me with a problem on their laptop, which naturally, did not work, the computer functions and works properly, but the sreen didn't. The story behind it is they started it up, went away and the computer died (screen went black), which I have been able to reproduce. I've changed the old display for a new one to which the inverter failed as well as I've guessed this is an inverter related problem. When I plugged the old screen back in, it works perfectly, but I can't seem to trace the inverter failure after checking the cables to begin with.

The video controller seems to be ok (as it outputed to another screen via the VGA connection) and as far as diagnostics, this is as far as I can go, I maybe able to source some other tools (multimeters, osciliscopes, etc), to determine the problem, but I just want some heads to be banged together to see if I've overlooked something. Has anyone else got any suggestions?

Dry joint somewhere which got disturbed when taking it to bits and is now connecting again? or an intermittent break in the wiring maybe, try opening and shutting the lid a few times and see if it reoccurs, or check if any plugs if there are any, are a bit loose.

 

[Wessex_Electric_Nutter]

Dry joint somewhere which got disturbed when taking it to bits and is now connecting again? or an intermittent break in the wiring maybe, try opening and shutting the lid a few times and see if it reoccurs, or check if any plugs if there are any, are a bit loose.

Dry joint is a possiblity, or intemitttent break, swinging the LCD doesn't reproduce the problem any more.... hmm Nor does tapping the area, so.... its alll a bit.... interesting. I don't recall any plugs being loose, the one on the inverter is hard to get off and the one under the keyboard was flat.

 

[JCitron]

Dry joint somewhere which got disturbed when taking it to bits and is now connecting again? or an intermittent break in the wiring maybe, try opening and shutting the lid a few times and see if it reoccurs, or check if any plugs if there are any, are a bit loose.

I was thinking the same thing. We used to call them cold solder joints where the solder cooled off before it had a chance to adhere to the circuit pad, or to the wire and only on the pad. Heat, wiggling around, and or any kind of movement can fix or break the equipment. This can also be cause by contamination on the lead (pronounced leed), or on the circuit pad on the PCB.

@ Wessex -

Try tapping or moving the display and see if it fails again. Intermittent problems can be rather pugnacious and difficult to track down. It's sometimes easier to fix something that's 100% broken than one that's intermittent because you think you've fixed the problem only because the device is working at that moment!

John

 

[Wessex_Electric_Nutter]

@ Wessex -

Try tapping or moving the display and see if it fails again. Intermittent problems can be rather pugnacious and difficult to track down. It's sometimes easier to fix something that's 100% broken than one that's intermittent because you think you've fixed the problem only because the device is working at that moment!

John

Funny, I had exactly that idea, I've tapped several times around the area where the backlight is, so I've decided the best way is to give it back, say I'ved tried, the old screen is now working but keep an eye on it and tell me if it fails again.