Odd problem with inverter board/backlight on Laptop

[loavesfishescomp]

Hello All...
So I have a client's laptop, and it had/has the faint images on the screen. I thought it was inverter board, so I bought one, installed it and it lit the screen up for about 5 minutes, then made a faint electrical sound, and went out. I plugged a spare back light into the new inverter board, and it stays lit (for about 5 minutes, then I shut it down-- not wanting to risk burning out another inverter board, which I forgot how I did that).
My question is: Is this a failing bulb? I thought bulbs would work, or not work... The color on the screen is perfect when it works for the 5 minutes the screen's bulb stays lit for.
Also... If I leave the external test back light in (same 15.4" size) might it burn out the new inverter board due to a (possible) difference in specs between the two bulbs?
Thank you in advance...
P.s. External monitor works fine.

 

[loavesfishescomp]

It's an older Compaq Presario R3000 if that helps. I'm stuck. Thank you.

 

[NYJimbo]

As a CCFL gets older it will draw more current or power. Most inverters will shutdown when they get hot from the excess draw, some might just die.

So yes, it does sound like the CCFL is killing the inverter but I dont know if your inverter will just shutdown and need a power cycling or if it will die.

 

[loavesfishescomp]

Thanks Jimbo, that sounds like the problem. I didn't mention this, but I installed a new inverter before this one, and left it plugged in (it felt like it was getting very warm) and it just shut down... and actually died. So I ordered a new one...
Sounds like I need to order a screen and quit using this CCFL... Cheers to you, NY

 

[XFalloutX]

In my experience only 10% of the time it is the inverter. I most of the time end up replacing both the screen and the inverter.

 

[NYJimbo]

I most of the time end up replacing both the screen and the inverter.

Yeah, but thats not really trouble shooting it. I mean you replace everything when you might not need to. What if it is the inverter, do you still replace both?. How do you know its the inverter, what test do you use ?

 

[trapped]

I just had a similar problem. Screen would stay lit for a few minutes and then go out. It was also making a weird high pitched noise. I went though about 4 inverters thinking the ones I was getting were bad. I finally replaced the bulb and it works perfectly now.

 

[usacvlr]

I've got a system here that I've written off and told the customer to pick up. I declare laptop from hell. Black screen.

Tried two other inverters both brand new.
Tried one other lcd cable.
Tried one other motherboard.
Tried one new LCD screen.
Disabled lid detect switch.

Still zilch. So, one of those items above is bad. I know it's not the LCD because the inverters will not light my test lcds. I know it's not the replacement board because the supplier verified it lit an lcd fine.
I doubt it's the two inverters since both were brand new albiet from the same source.
So, I suspect the new lcd cable is bad but I'm not going to waste any more time on this thing. I'm refunding them partially and writing it off.

 

[NYJimbo]

I've got a system here that I've written off and told the customer to pick up. I declare laptop from hell. Black screen.

Tried two other inverters both brand new.
Tried one other lcd cable.
Tried one other motherboard.
Tried one new LCD screen.
Disabled lid detect switch.

Still zilch. So, one of those items above is bad. I know it's not the LCD because the inverters will not light my test lcds. I know it's not the replacement board because the supplier verified it lit an lcd fine.
I doubt it's the two inverters since both were brand new albiet from the same source.
So, I suspect the new lcd cable is bad but I'm not going to waste any more time on this thing. I'm refunding them partially and writing it off.

When you have replaced just about everything I have to wonder what sequence these things were done in.

In theory if you replaced the LCD, the cable, the motherboard, the lid switch and the inverter ALL AT THE SAME TIME then you replaced everything. However I am sure you were replacing them and going back and forth and some sequence might have got past you. Dont get me wrong, I would throw in the towel too at some point, but it appears you have replaced everything at some point so in theory this thing should be working.

 

[loavesfishescomp]

So I went big and replaced the bulb with another used one I had lying around... and it does the same thing!? after about 2 minutes of being lit, it slightly flickers/dims and the inverter board makes this slight electric squealing sound that fluctuates with the picture. Odd to me! I have no clue.
It might be the cable someone mentioned? This is highly uncommon I am * guessing*, without enough experience to back that statement up.
...And this thing has 30 screws on the bottom.

 

[loavesfishescomp]

And another thing. When I decrease the brightness on the screen, the problem doesn't happen.

 

[NYJimbo]

So I went big and replaced the bulb with another used one I had lying around... and it does the same thing!? after about 2 minutes of being lit, it slightly flickers/dims and the inverter board makes this slight electric squealing sound that fluctuates with the picture. Odd to me! I have no clue.
It might be the cable someone mentioned? This is highly uncommon I am * guessing*, without enough experience to back that statement up.
...And this thing has 30 screws on the bottom.

You put a new CCFL in the LCD or just hung it off the wires ?.

The inverter squealing is almost always because of the CCFL. It probably cannot provide the power needed and shuts down. I would think a new CCFL would clear this up but if its still doing it then you might have some weird issue with the motherboard.

Too many variables here, but I still tend to think it is not the video cable, but its possible the motherboard is being "taxed" and the inverter cant handle it.

Gotta walk away from this because I cant see it myself and try some stuff but if everything you are saying is accurate the cheapest next step would be the video cable.

 

[loavesfishescomp]

I understand what you're saying. I installed the used bulb into the bottom of the LCD screen, and then installed the new inverter board, & buttoned it back up.
I suggested that because this laptop is so old, that it really isn't worth spending much money on; partly because it will take me a lot of time to replace a video cable, and that might not even be it.

Thanks a lot Jimbo.