Laptop Inverter Problem?

[quizbowler1057]

A few posts ago I mentioned a laptop that I fixed, then came back three days later. Now I'm finding I need a little help on it:

Background: A client brought over a PC while I was out of the office and didn't leave much info on it. Quick test showed it was a battery issue. Battery and AC, laptop worked fine. No AC, laptop shut down after a second or two.

Replaced the battery, sent it back to its owner. Three days later he comes back, says the screen is dark. Tried the BIOS and keyboard brightness buttons to no avail. Dead lamp. Let it sit for a few days while I do some other stuff, come back to it, power it on, full brightness! Power it off, power it back on, no backlight.

Maybe the inverter's fritzy. Order a new one, replace it, same problem. Ok, now I'm ticked. Take the screen apart, no black around the bulb, no obvious signs of damage on the cables. Checked the AC adaptor, the power cord and the power jack - all look fine. I have to build a lamp tester still to test CCFLs and I'll get to that soon, but short of a trying a new lamp, what's left? All mobo connections were solid as well - though that has nothing to do with brightness.

It's an Acer Aspire 3000. I suspect the gentleman that owns it tried booting it up in his cold car, but can't prove it. That would have shocked the inverter anyway which I've already replaced.

 

[PcTestCard.com]

Hi,

try use external monitor to test the laptop.

Also check the backlight and the connectors.
Besides make sure your KB "FN" key is working.

Hope this helps!
Bill

 

[usacvlr]

If the system outputs to an external monitor as the above poster said or if you see drive activity(lacking a monitor) then most likely it can be easily fixed depending on the model. What model is it?

 

[quizbowler1057]

Sorry, took a vacation.

It's an Aspire 3000. The inverter was replaced and it didn't do anything. It still has intermittent backlighting. We're replacing the lamp as I type. New policy, since they are so cheap, any PC that comes in with faint display is going to get the inverter and lamp replaced at the same time.

 

[usacvlr]

You may find that it is not the lamp..however what it actually may be is a secret and I'd have to ,, well you know the joke.

 

[quizbowler1057]

Well it's actually a very weird problem:

New lamp and new inverter doesn't work.
Old lamp and old inverter doesn't work.

New lamp and old inverter works.
Old lamp and new inverter works.

The original inverter and the new inverter are physically and electrically identical. The original lamp and the new lamp are physically identical.

Over the weekend I'm going to make a little jig up to test lamps and make this easier in the future, but this whole situation was weird.

 

[i2omani]

newer HP laptops having the same issue , it turns out that the have a defect.. symptoms: black screen! same as your situation here...but its not the inverter or the back light ... ready " its the Lid switch" disconnect it and it will work just fine weird huh so i don;t know if you having the same thing here.

hope that will help a little

 

[usacvlr]

newer HP laptops having the same issue , it turns out that the have a defect.. symptoms: black screen! same as your situation here...but its not the inverter or the back light ... ready " its the Lid switch" disconnect it and it will work just fine weird huh so i don;t know if you having the same thing here.

hope that will help a little

don't forget to kill him... Nearly every Acer that comes into the shop has this problem... Cheap little piece of crap switch that sticks.

 

[quizbowler1057]

Sorry guys I wish it were that simple. Besides a stuck switch would mean it wouldn't display an image at all, not display an image with no backlight. I had a gut feeling after monitoring the laptop for a few hours.

I let the laptop sit on AC all night, making sure the battery was firmly seated (keep in mind this is a brand new replacement battery). I turned the laptop on today and, voila, no back light again. I unplugged the AC and let the laptop run. After about 5 seconds it completely shut off (same problem as before the battery replacement).

After it shuts off I can turn it back on but it does the same thing. Attempting to go to Safe Mode yeilds the same results as does "Last Known Good Config". The PC was cleaned with air in a can and I don't believe it's an overheating issue.

The key thing here is that once the battery has drained slightly whether you use the battery or plug the AC back in, I get a backlight.

 

[quizbowler1057]

Even more info:

I started thinking beyond a simple electrical issue. Letting the PC idle on the menu: Safe Mode, SM w/ N, SM w/ CP, LKGC and Start Normally (with no plugged in AC) prevents the computer from shutting down, meaning it's either a Windows issue or an overheating issue when the computer starts to try to load Windows. I still have a backlight.

So are there multiple problems? Does a full battery with/without AC knock out the backlighting? I'm going to load a linux CD and attempt to run the PC to see if it shutsdown due to overheating. I'll post more later, I want to go enjoy my vacation.

 

[usacvlr]

The screen will still draw even if the switch is turning off the inverter. The inverter just lights the lamp and the switch usually has no effect on the lcd itself.

 

[Rider]

Have you tried disconnecting the switch yet? I wouldn't rule out a power problem either. Are you sure the battery is charging? You may have a bad power jack.

 

[quizbowler1057]

Checked the switch. Even with a dim LCD hitting the switch turns off the picture. Even if you shine a flashlight in the corner to backlight the image, the switch turns it off which is why I think the switch doesn't just affect the light.

The jack is fine as is the power cord, tested both.

Setting the restarting issue aside, I let the battery run all the way down to dead by leaving the PC on a DOS menu. I then charged it back up again. When the battery is fully charged, the PC has no backlight. If allowed to run for even a few minutes with no AC, the backlight comes right back on, sometimes without having to turn the computer off at all.

 

[usacvlr]

It sounds like the driver circuit for the inverter is bad. Usually the inverter gets 5 volts or so from the board along with some control signals to control brightness. Somewhere in there is the problem but frankly it's not worth troubleshooting to find it. New board.

 

[i2omani]

lid switch

have you disconnected the switch or no?
try to solve 1 issue at a time, you can't just solve all of them at one time if so m$ is hiring

do you have a structure you are following, or you just hoping you will stumble on the correct fix? am not trying to be rude... its like networking issue problem were a host is not getting an ip address , and you start your troubleshooting form the L7?? although it might fix it but you will not have an ip if nothing is at L1 so you will work your way from L7 .....L1 and see that there is no cable connected?

rip the whole thing apart and connect it to an external LCD. all what you need is CPU and memory, i don't think you need the HDD.