Laptop screen light turns off after a minute or two.

Compaq R3000 laptop.

This laptop came to me several weeks ago with display lighting up only a few seconds after powering up, then going out.

First Attempt: I replaced the inverter and all seemed to work well for a week or more. Then the same result as above.

Second Attempt: I replaced the CCFL and it worked for about fifteen minutes, then same as above again.

Third Attempt: I replaced both the CCFL and the inverter at the same time. It worked for about ten minutes and then began a rapid on and off flashing of the screen about three- or four times a second, increasing gradually to about eight times a second. The rapid flashing lasted about a minute and then it went off completely.

I turned it off and back on and the screen worked fine for about three minutes. Then it repeats the same flashing process again.

I can see a faint image on the screen in all the above scenarios and when it is connected to an external monitor, it works fine.

All parts replacements were bought from ebay "Top Rated" sellers and all parts were advertised as new, and looked new. The CCFLs both came with pre-attached wiring harness. Parts all came from different dealers each time.

What could be causing this?

 

Power - or rather, bad power would be my guess. And sadly, I would suspect it is the power regulator/charging circuits inside the notebook - that is, a motherboard problem. This assumes you were using the correct replacements parts for the inverter and light.

 

Bill,

It looks like you have guessed it. I ordered another inverter which came today. The first thing I noticed when removing the last-installed inverter was that the plastic shrink-wrap was misshapen and torn characteristically of overheating. I installed the new inverter and after about two minutes, the screen dimmed as I heard a faint high-pitched hum and the inverter was very hot to the touch.

It may be each inverter took progressively less time to fail, maybe because the power supplied from the main board was getting progressively further off specs. Or maybe the inverter is not the correct one for this CCFL.

As for the parts being the correct ones, I have no way of verifying that independently. Both CCFLs came from different dealers and were the correct length for the screen. The inverters came from different "Top Rated" dealers and were advertised as "new ".

The CCFLs and the inverters were advertised as being for this R3000 model and for the 15.4" screen. As far as I know, there were only two screen sizes for this model and 15.4 was one of them. One peculiarity is that the naked screen measures about 15.55 inches and the bezel opening about 15.4.

It appears this laptop is good for only when connected to a desktop monitor.

 

At least that way, you can use a larger screen, full sized keyboard, real speakers, and mouse! That said, if the computer works fine otherwise, then not sure the power problem is with the notebook's charging/regulator circuits, but rather power to the monitor. At any rate, too much heat typically indicates too much current, typically caused by a short, or near short somewhere. Keep a close eye on it.

Sorry I did not have a magic pill to fix all.

 

Either that or improper voltage being supplied to the inverter.

 

Good point - but then that would be two bad inverters - certainly possible, but it makes you wonder.

 

That kind of heat can have two causes. Either the CCFL is demanding more current than the inverter is designed to deliver, or the motherboard is delivering higher voltage than the inverter is designed for.

In the realm of possibilities, there is one other. Based on the fact the screen works fine for a minute or more, there is the possibility the inverters I have been getting could be designed for a fourteen-inch screen instead of my fifteen-inch.

It seems strange that I could get three inverters from three dealers that were all designed for the smaller CCFL. But the manufacturers of these items are limited; maybe there is only one. Maybe they are marketing those inverters incorrectly to the retailers and all the retailers are getting then from the same source.

Of course, all of this is academic at this point because I don't have any way of independently verifying whether these inverters are the correct size. Then there is the consideration that I know for a fact this is the same symptom that presented after several years of perfect operation with the original parts. That would seem to go against the "wrong inverter" theory.

 

Well, not sure it is worth anything, but I agree with your assessment.