Backlight goes out as soon as I hit the Login Screen

[Ilikemonkeys12]

Hey all. I just bought a used Macbook pro 13, 2009 model with a bad backlight. I've read about inverter board, inverter cable and logic board issues but I'm not sure what to look at in my specific case. There are two things that it does:

1. If I turn the computer on - The backlight will flicker once and then go out. The computer boots normally otherwise and if I shine a light on the display I can use it just fine.
2. If I do the SMC reset and then turn it on - The backlight will work just fine until I get to the login screen. The backlight will flicker immediately before going to the login screen and then is off.
3. If I hard reset (hold down power switch) and then turn it back on - The backlight works fine. I'll get the Apple logo and the little status bar below it but as soon as it goes to the login screen the backlight goes out.

If I were a betting man I'd assume it's a driver or software fault but I'm stumped. I know my backlight actually works. I think I can rule that out. So what's left? Any help is obviously appreciated. I'd love to get this working. I bought myself a new i7 13" and my wife is so jealous that I got this used one for her. Just got to get it working...

Edit: I have done the PRAM reset as well. No difference.

 

[Ilikemonkeys12]

So I've been searching exhaustively for a few hours now and can't find any other reports of the backlight staying on until you get to the login screen. That sucks.

Has anyone seen this happen before? Even if you don't know what caused it, I'm just curious to see if anyone else has seen it. It's driving me nuts.

Can someone explain what the symptoms of a failing inverter are? Despite searching through about 5 years worth of posts, I can't seem to find that info either.

 

[Hamilton1963]

Click on the Apple
Click on System Preferences
Click on keyboard
Make sure there is a check mark on "Automatically Illuminate keyboard in low light"
And make sure it is set to never turn off. I hope this can help.

So I've been searching exhaustively for a few hours now and can't find any other reports of the backlight staying on until you get to the login screen. That sucks.

Has anyone seen this happen before? Even if you don't know what caused it, I'm just curious to see if anyone else has seen it. It's driving me nuts.

Can someone explain what the symptoms of a failing inverter are? Despite searching through about 5 years worth of posts, I can't seem to find that info either.

 

[Ilikemonkeys12]

Click on the Apple
Click on System Preferences
Click on keyboard
Make sure there is a check mark on "Automatically Illuminate keyboard in low light"
And make sure it is set to never turn off. I hope this can help.

Sorry, I should have mentioned that I'm referring to the display backlight, not the keyboard.

 

[Ilikemonkeys12]

Well I'm not going to continue to spam the board if no one has any clues about what the issue is. So this is my last bump and hopefully the morning crowd sees it. Truthfully I thought someone was going to post within 5 minutes and say something like "Oh yeah... It's xxxxx" but no such luck I suppose.

If anyone has any guesses and they're right I'll Paypal them $50. I'm just not sure what else to do and I'm not going to start throwing parts at it ad nauseum.

 

[blueroom]

Time Machine then reinstall the OS, if this fails to fix the backlight then it's busted. iFixit.com or a trip to the Apple store near you.
PS if you don't have a backup drive now would be a good time to get one.

 

[shardey]

Put an OS X install disc, or the laptop discs that came with you laptop in. This may help you narrow it down.

 

[Detrius]

There's no software reason for the backlight to go out when it gets to the login screen AND to go out immediately after it's powered up. For proof that it's not software: boot the machine holding down the option key and leave it sitting there. The backlight will go out anyway. You almost certainly have a bad LCD.

The inverter is for fluorescent backlit screens. LED backlit screens therefore don't have an inverter.