Screen Too Bright and Lacks Contrast

Question

Screen Too Bright and Lacks Contrast

Haven't seen this exact problem mentioned. I have a iMac G4 that's about 3 years old. Yesterday I noticed that the screen seemed a little brighter than it had been. Today, it was so bright that text was barely readable and the letters appeared to be ringed with red or other color artifacts, and images were way too light. Turning down the brightness in the Control Panel only darkens the screen and does not help readability issue. Tried resetting PRAM, but it seemed to have no effect. Any other ideas? Might this be an inverter board issue that I've read about on this board? Don't want to spend a fortune repairing this machine though it has been trouble free up to now.

I have a suspicion that a freak (this is December, after all) lightning storm the other night might have been the culprit, as I discovered the screen issue the next day.

PowerBook G4, Mac OS X (10.4.3)

Posted on Dec 6, 2005 8:24 AM

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Answer 1

Dec 6, 2005 8:41 PM in response to Nick Giamarino

First go to system prefs>universal access and be sure the contrast slider is at Normal. If that didn't do it:

Go to system prefs>displays>color calibrate and check the Expert Mode box. Click past the first screens with the apples on them without changing anything. When you get to gamma, check the box that says "Use Native Gamma", then click through to the end and name and save the profile.

If neither of those helps, you can try running Profile Repair in the colorsync utility (applications>utilities) and if it still looks bad (check with other users, too) then it's probably a hardware problem.

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Answer 2

Dec 7, 2005 1:32 PM in response to Nick Giamarino

It's the monitor itself that has gone bad. It's gone totally grey now. I connectd an old ViewSonic CRT monitor, and the computer works great. I'm just having a hard time getting used to the clunky size of the CRT! I want my 15" Flat Panel back again!!

That being said, does this narrow down the actual culprit any? Since the computer itself seems to be working fine, I assume that the logic board is still OK. Could it be a bad inverter board after all? If so, how do get at it, and where can I get a new one?

I don't really want to turn the iMac into a 'headless mac".

PS: what tool do I need to remove the tiny fasteners used on the monitor? I have a bunch of hex wrenches, but none that tiny!

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Answer 3

Dec 8, 2005 12:08 PM in response to Nick Giamarino

Hi Nick,

Bad inverters and backlight issues tend to give you a black screen. If it's the backlight, you can still see a faint image if you shine a flashlight on the screen.

Given that you can run another display OK, it's not the graphics card or the motherboard (they're both integral in the iMac anyway).

What you are experiencing could have more to do with the articulating monitor arm. If you want to try to get your flat panel monitor back, it's definitely worth your while getting it to a repairer for evaluation - it could just be some bad connections.

Cheers!

Karl

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Answer 4

Dec 8, 2005 12:58 PM in response to Karl Texler

Thanks for your input Karl. I tried looking into the screen with a flashlight, and no image is visible at all. I noticed, however, that the small indicator light located at the bottom right hand corner of the screen frame/bezel still glows, and the "Brightness" slider control in the System Preferences > Hardware >Display makes the flat screen lighter or darker (but oddly has no effect on the temporary CRT monitor I'm using). Might this mean that the backlight(s) are still functioning?

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Answer 5

Dec 8, 2005 2:57 PM in response to Nick Giamarino

Hi Nick,

It sounds as though the backlights are OK. You are getting a "black" video input, so the signal is not getting from the (functional) graphics card to the display.

Having it professionally attended to will rule in/out inverter and physical connection issues.

Cheers!

Karl

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Answer 6

Feb 28, 2006 6:32 AM in response to got_the_feelin

I too have a iMac G4 with a 15inch LCD attached with a tube, and it turns white when I leave it on for too long, then it has to sleep to get its normal color back. Anyone know the answer here??
Bruce Bodner
bebgsurg@massmed.org

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Answer 7

Feb 20, 2006 12:31 PM in response to Nick Giamarino

Did you reslolve this issue in the end? If so, how? I have exactly the same problem!

Imac g4 Mac OS X (10.2.x)

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