Macbook screen dimming, flicker!

May 31, 2009 5:02 PM

My Macbook Core Duo 1.83 GHZ experiences random dimming of the screen, like a flicker, from time to time. I just bought it from my sister in law and installed Leopard on it. She said she'd never had this problem while she was using it, when it had Tiger.

I've been reading up on the issue on various Mac forums and some people say it's a screen power inverter issue, which is a hardware issue and would cost money to fix, since the laptop has long been out of warranty.
Others say that the automatic light sensor should be disabled, from somewhere in System Preferences/Display, but I don't have that option.

The dimming and brightening does not occur all the time, but still, it's pretty annoying when it occurs.

Is there a fix for this?

Thanks MeFi!

posted by spacefire to computers & internet (17 comments total)

Want my guess?

You are, inadvertently and without knowing it, jiggling the power connector. By default, OSX uses a different backlight brightness setting when it's running plugged in than when it's running on battery. So, when you jiggle the cable (like it's unplugged for about a quarter to a half second), the OS dims your screen and then brightens it when it's plugged back in. By installing a new OS, you reset that setting to default.

I'm wrong if it happens even when the machine is running on battery power. But, if it only happens on AC power, and you use the machine on your lap (or bed, or couch, or chair, or carpet), it's my guess.

My wife also points out that it needn't be the magsafe power connector itself. It could be an intermittent disconnect anywhere along the power adapter.
posted by Netzapper at 5:10 PM on May 31

sorry. but it also happens when on battery power.
posted by spacefire at 5:19 PM on May 31

This also happens to my laptop but only when the screen is at a pretty low brightness setting. I don't think it's a software issue, but perhaps the upgrade to Leopard changed your power settings and the screen gets dimmed more often?

I'm pretty sure it's the inverter. If your problem is anything like mine, check to see if this is happening when the screen is on full brightness and possibly turn off auto-dim if it's the case.
posted by bsdfish at 5:25 PM on May 31

It sounds suspiciously like the problem my black MacBook developed. It was more like the screen would oscillate rapidly between the AC brightness and battery brightness. And, like you, it happened while on battery. It was intermittent.

The ultimate answer the inverter. I have AppleCare for the unit but since was intermittent Apple didn't see it the first couple of times I brought it in. Finally, one of the service people saw it as I was attempting to demonstrate it for them and they replaced the inverter.

m
posted by tcv at 5:39 PM on May 31

This happens to my Macbook and has done so pretty consistently for about 2.5 years. I never got it replaced and it's never gotten worse. It mainly happens when the screen is cold.
posted by proj at 5:53 PM on May 31

I've had similar issues a couple of times after large point upgrades to 10.4.x. What has sorted it for me is to:

• Do a "Repair Permissions"
• Reset the PMU (or whatever it's called on Intel Macs; despite owning a Core2Duo MacBook I can never remember the new term...)
• Create a custom profile in 'Energy Saver', reboot, then go back to the profile you normally use

I don't think MacBooks ever came with an ambient light sensor, only the MacBook Pros...
posted by Pinback at 6:32 PM on May 31

Yeah, this sounds like a problem my MacBook had. Whenever the flicker started happening, I found that I could make it stop by adjusting the angle my screen was at. If the screen started flipping out, I would push it back a bit and the flickering would stop at the new angle. It did this for about a year or two but doesn't do it anymore. Go figure.
posted by losvedir at 6:39 PM on May 31

I had a similar problem on the same model, somtimes at random and often when the computer was moved .As time went on the back light would start to go off completely after the flicker.

The problem for me turned out to be a loose wire from the inverter and was pretty easily fixed.

It is sort of a hassle to get the case open, but if you are comfortable with a little computer surgery, it might be a worth your time to open it up and check the connections.
posted by St. Sorryass at 6:42 PM on May 31

System Preferences > Displays > Display > Automatically adjust brightness when ambient light changes.

System Preferences > Energy Saver > Options > Automatically reduce the brightness of the display before putting to sleep

These are the two 10.5 (Leopard) settings I know of which relate to automatic adjustment of screen brightness. If these are both unchecked and it still does it, it's certainly a hardware issue.
posted by cj_ at 7:10 PM on May 31

My girlfriend's MacBook of a similar vintage had the same problem (with Tiger, btw). She took it to the Apple Store for an unrelated issue and mentioned it, and they said that it was the inverter and repaired it. Since then, there hasn't been any flickering, and the screen tends to look a lot better in general.

She had AppleCare; I think the repair would have been kinda expensive otherwise.
posted by miraimatt at 8:51 PM on May 31

Want my guess? You are, inadvertently and without knowing it, jiggling the power connector.
MacBooks all have that magnetic cord connector thing, so there's no real cord jiggling to be had—the cord's either firmly plugged in, or firmly not.

I just took my MacBook in for this problem last Friday. The trouble I was having was maybe once a day, the screen would go black for about a quarter-of-a-second and then come right back on. I have AppleCare (through next February), so I went online, booked a Genius appointment, and took it in.

The Genius guy said that this was a known issue and that it usually resulted in one of two things: what I was seeing, or a constant wavy brightness on the screen. They had to replace the inverter thing that is located inside the hinge part of the MacBook. They had the part, so the repair took about 5 hours. But again, this machine was still under AppleCare so the repair was free.

I don't know if you can buy AppleCare for the MacBook now (or if Apple'd be suspicious if you bought AppleCare for an old computer and then brought it in for repair the next day) but if you could, it might be cheaper to do that than to take it someplace to get it repaired. (I recall when I had a hard drive installed on my old iBook, the Mac place that did it charged me about $80 an hour just for the labor)

Unsolicited advice to previous posters who've noticed this problem: if you have this problem from time to time and you have AppleCare I'd take your machine in. It's a quick one-day fix. The issue means you have a bad part in your machine (which is at best going to limp along, at worst, going to get worse or fail—probably the day after the AppleCare runs out). Use your AppleCare free repairs while you can!
posted by blueberry at 9:18 PM on May 31

You can only purchase AppleCare within the first year of ownership of a Mac. After one year, a computer is not eligible. In cases where a person doesn't know the purchase date of a computer, Apple can tell the manufacture date from the computer's serial number. This is to prevent people from doing what blueberry is talking about: paying for AppleCare on an older machine to fix a very expensive part (LCD, logic board, etc.).

spacefire, I see you're in NYC. If you email me or IM me (info in my profile), I can give you some information on NYC area Mac shops and individuals that do out-of-warranty repairs.
posted by mrbarrett.com at 5:04 AM on June 1 [1 favorite]

@mrbarrett:

thanks for the offer, I'd rather not spend any money on this right now...I was wondering if there was a DIY fix for it or maybe it was a software issue.

I said, the problem does not occur constantly, rather, it seems, it happens about five minutes after every restart, for a few minutes, then it goes away..again like many posters said this could be from a loose wire or from the inverter.

I already resetted the PRAM and NVRAM but that didn't alleviate the issue. I will try the PMU reset next.

If I were to replace the inverter myself, would that be cheap? Maybe less than $30?
Would it be doable by a relative novice? I have taken Macs apart before and swapped parts, and I have a busted screen iBook G3 for 'practice', but I've never soldered anything.
posted by spacefire at 8:52 AM on June 1

Here's a MacRumors forum post where they talk about replacing the inverter and mention two possible ways to go about it. I think for something like this, you'd want to make sure that you have all of the proper tools, and a free stress-free afternoon with a big clean tabletop to work at.
posted by blueberry at 12:26 PM on June 1

my mac had the exact same fault, developed after three months of ownership. I took it to the school repair lab as I couldn't send it away to Apple (and was nowhere close to an Apple Store), and they fixed the fault by getting to the invertor, seemingly not finding a problem and putting it all back together again. therefore I suspect mine was a loose wire which they tightened in trying to find the problem. They never even phoned Apple, I just printed them off everything I found on the internet about the fault, so they knew where to look. You could probably try and find someone to do the same or try yourself. The fault never came back for me, and that mac is two and a half years old now. Now hoping my new one doesn't do the same!
posted by nunoidia at 12:30 PM on June 1

Mac Book Pro's autodim when the room itself gets dim. Sometimes the sensor is a little aggressive. I had issues when I was working in a sunny office and the trees would blow in the breeze, casting complicated shadows on my Mac. Luckily I now work in this fabulous cube with completely uniform lighting.

Uh, yeah, it's probably the inverter.
posted by chairface at 4:11 PM on June 1

Purchased from Apple (via an Apple Authorized Repair Center, or perhaps on the grey market):

Inverter board = $29.00
Inverter cable = $7.00

The time it takes for this repair is the killer. Were this in my hands, I'd want a solid two hours to get this one done. It's not quite as involved as replacing the LCD, but it's up there. I'd ask for $75/hour, but people's prices vary.

The other problem is that while we think this is the inverter board, it's possible that it's some other component that's failing. Yes, the odds are great that it's the inverter board, but the only way to guarantee a fix is to replace parts until it's fixes, which sometimes means a higher cost.

And you can reset your PRAM, SMC, PMU, and reinstall your OS until you're blue in the face, but if it's actually the inverter board (as we think it is), the only fix is to replace the failing component.
posted by mrbarrett.com at 4:11 PM on June 1