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mad cow disease · Sep 23, 2010, 02:24 AM

I have a used black Macbook I recently purchased. The backlight seems to turn on and off randomly depending on where force is applied to the screen and where the screen is positioned at 90 degrees or so. Fully extended, no problem. Runs for hours without so much as a flicker.

Sounds like an inverter problem, but given that the flicker has to do with the angle of the hinge, I am thinking a partly or shorted cable. Anybody with experience doing this sort of repair? Is it doable? I've built PCs from scratch so I am comfortable messing around with the innards, but if it's going to require a complete disassembly I may just live with it as is.

Thanks in advance.

Spheric Harlot · Sep 23, 2010, 03:35 AM

Replacing the display cable requires a Complete Disassembly.

I have the same issue, and while I have friends who do this kind of stuff, they've made it clear that asking them to do this would be heavily stretching the limits of goodwill.

Waragainstsleep · Sep 23, 2010, 04:27 AM

Its a pain in the ass to rebuild a MacBook display. Its not hard so much as fiddly. For the record it could also be the inverter cable which is faulty and/or the LVDS.

mad cow disease · Sep 23, 2010, 10:55 AM

Hmm. I hesitate to disassemble the entire thing, although the parts are cheap. I am still leaning toward a crimped cable, given that the screen is fine at a certain angle. Would popping off the top case allow me to verify this? Also, any way to narrow it down to one or the other?

Everything I have seen thus far seems to point to inverter...

olePigeon · Sep 23, 2010, 11:23 AM

I had a MacBook sent in for repair that had a flickering display, and the technician replaced the screen. It still flickers. Going to send it back in.

ibook_steve · Sep 23, 2010, 09:43 PM

Do the new LED-based backlights still use an inverter? If so, why would LEDs require high voltage?

It's been ages since I've opened a top case, and I don't know much about how LED backlights work.

Steve

ghporter · Sep 23, 2010, 10:11 PM

I can't see why an LED illumination system would require an inverter. The inverter creates an AC (or pseudo-AC) signal that is used to step up a low voltage to a higher voltage for rectification back to DC, or for direct application to an AC device. LEDs are pure DC devices, and low-voltage DC at that.

Wiskedjak · Sep 23, 2010, 10:23 PM

I know so many people who have display issues with their Mac laptops, myself and present company included. I don't think my next computer is going to be a Mac laptop.

Waragainstsleep · Sep 24, 2010, 04:42 AM

Mac laptop screens are fine. PCs have just as many issues, the parts are pretty much the same.

LED backlit screens do not have inverters, they have LED driver boards. Black MacBooks are NOT LED backlit though. The inverter is in the clutch cover with the hinges. The LVDS (which has USB as well) goes through the left hinge, the inverter cable and mic cable go through the right hinge. I have seen inverter cables cause this issue before. There is a small chance its the panel but these are not expensive if you source one somewhere other than Apple. eBay is your best bet.

To confirm your theory, you could remove the display. Again its fiddly. There isn't much slack on the cables. You want to get it so you can physically wiggle the cable with your hand while its running.

Spheric Harlot · Sep 24, 2010, 05:28 AM

Originally Posted by mad cow disease

Hmm. I hesitate to disassemble the entire thing, although the parts are cheap. I am still leaning toward a crimped cable, given that the screen is fine at a certain angle.

FWIW, this issue has appeared on laptops for about ten years - I remember that the first chiclet iBook G3s would eventually develop this flickering at certain angles - and it's almost *always* been the cable failing due to the hinge being constantly opened and closed.

Wiskedjak · Sep 24, 2010, 08:20 AM

Originally Posted by Waragainstsleep

Mac laptop screens are fine. PCs have just as many issues, the parts are pretty much the same.

Yes, but Apple's laptop designs seem to push the limits of the parts further than many PC laptops.

mad cow disease · Oct 2, 2010, 01:41 AM

I have gone parts shopping, and wow, they're cheap! The inverter is like five bucks! The LVDS, a bit harder to find, but still cheap. This is on eBay, of course.

I notice there are a lot of parts sellers from China shipping FREE. From China...which makes me a bit nervous as to the authenticity/reliability of the parts. These parts together will cost upwards of $100 on iFixit and Powerbook Medic, so I am leaning toward eBay...but then, this repair takes ~2 hours or more so I'd rather not have to repeat it.

Anybody care to share experiences from eBay-bought parts? Thanks.

wannadance · Dec 24, 2010, 01:48 PM

I have had a similar problem with the screen randomly dimming. After a bit a surfing for clues, someone said that the 2 ambient lighting detectors are behind the 2 speaker grills. It did seem that when I had the problem my hand was near the speaker grill. I tried covering both speakers with my hands and voila, the screen dimmed. In display settings in system preferences, I unchecked "Automatically adjust brightness as ambient light changes". Again, I covered both speakers and the screen did not dim.

If this is not your issue, I hope yours is as easy to solve.