MacBook permanently lost brightness control after PRAM reset?

[user1690]

Hello all!

So my Mid 2010 MacBook required a PRAM reset after it started acting strange (got itself stuck in a bit of a boot loop with the Recovery HD, so to get out of it i tried a PRAM reset), however ever since then my MacBook will NOT turn on the screen AT ALL until OS X has loaded, the only way i could even find out that the screen wasn't faulty was to boot up a old Lion DVD i made a while back because once that loaded the screen sprung to life (I let out a sigh of relief!)

But this means i can no longer take advantage of things like FileVault and such because as well as the screen being off now at boot, the Mac doesn't seem to respond to anything other than me pressing the C key to boot a disk, or the Mac booting the main hard disk.

Has anyone experienced this type of problem? Even in OSX i have no brightness control and i don't remember the MacBook ever listing the display as "SPDISPLAYS_DISPLAY".

I thought maybe a few system files had gone bad, so i took advantage of the Lion DVD i had made a while back and just did a fresh install (for anyone wondering its just the InstallESD from the Lion installer, burnt to DVD, no shady business) but still the same.

Don't get me wrong, the MacBook works otherwise, the Nvidia 320M is fully recognised and usable.

Any info on this would be appreciated!

Heres what i have already tried,

SMC Reset (10+ times (not all at once of course!))
NVRAM Reset (10+ times (not all at once of course!)
Removal of battery from MacBook and waiting 30+ minutes
Trying with no battery and just magsafe
Entirely new installations of OSX (Tried Lion, Mountain Lion and Mavericks)
Inspected hardware itself, cables are all connected, inverter is fine because screen works perfectly when OSX has loaded!

 

[SteveJUAE]

NVRAM you would think is the culprit but sorry I do not know enough to be able to assist further

 

[user1690]

NVRAM you would think is the culprit but sorry I do not know enough to be able to assist further

Yeah this is rather baffling, i think im going to have to just suck it up and deal with it, the MacBook still works perfectly but just no more filevault or anything other than the C key working at boot up. (If filevault is enabled all i'll get is the black screen and i cant even login blind, because the keyboard doesnt initialize (Except for that C key, caps lock and everything else doesnt work))

I have a vague suspicion to what might be going on, i remember that OSX has a hidden partition called EFI, and inside here are relevant files a Mac needs at bootup in order to be able to handle things like Filevault, graphics, recovery, etc so i might take a look here and see if maybe anything is missing or corrupt. That seems unlikely though since this is a new installation but one never knows until they try, right?


EDIT: Well that was a bust, i give up. The MacBook works at least 95% , as i say just no FileVault, and i discovered as well no internet recovery or even the built in Recovery HD. They are there, just not accessible now. so i've made a Mavericks install DVD the same way i did for Lion, i can use the disk Utility there to create and restore backups if need be.

Still, if anyone has any insight as to what may be going on then i'm all ears!

 

[SteveJUAE]

What about getting a cheap small new HDD and installing that from scratch even if it's just to eliminate that side

 

[user1690]

What about getting a cheap small new HDD and installing that from scratch even if it's just to eliminate that side

Well i have a USB drive spare, i tried that and still, no dice. Thanks for the suggestion though! I think the NVRAM has just forgotten there is a display/backlight connected, its not even recognised as "Built in Display" which im sure is what its supposed to say! That may also explain why when OS X loads up the screen comes back to life because the Nvidia drivers kick in and take over from whatever would have been driving the backlight/display before. Also i made another discovery, allowing the computer to go to sleep means the backlight stays off when i wake the machine back up, and since i've lost brightness control i'd have to shine a light real close to the screen to find the shutdown option and do that so that when i start back up the screen works again.

 

[SteveJUAE]

Well i have a USB drive spare, i tried that and still, no dice. Thanks for the suggestion though! I think the NVRAM has just forgotten there is a display/backlight connected, its not even recognised as "Built in Display" which im sure is what its supposed to say! That may also explain why when OS X loads up the screen comes back to life because the Nvidia drivers kick in and take over from whatever would have been driving the backlight/display before. Also i made another discovery, allowing the computer to go to sleep means the backlight stays off when i wake the machine back up, and since i've lost brightness control i'd have to shine a light real close to the screen to find the shutdown option and do that so that when i start back up the screen works again.

That's what I thought on the NVRAM, there is some info on editing a file to cause the system to display the right screen name etc on some of these hackintosh sites it seems, have a google but I'm not sure if it will help directly but certainly give some more insight in to the workings of the NVRAM