12-28-2007, 02:16 AM

2Ghz Intel Core Duo 20" White iMac Mac OS X (10.4.9)


Hey everyone.

Recently, my white iMac has been locking up a lot lately (forcing me to hard-reset, boo) and horizontal lines have been appearing. It freezes most often during more graphically-intense applications like games and Pro Tools. It's not the regular Mac freeze, where the grey dialogue box politely and multi-ligual-ly informs you that you need to reset. When my computer freezes, things just lock up, or the screen will go black.

I thought since I had not done a whole lot of computer maintenance since the day I bought it, there was a possibility it was just a horrible software glitch.

So I zero'd my hard drive and reformatted. Almost immediately the lines returned. Interestingly enough, I don't need a digital camera because these awful lines can get captured by screenshots.

The lines are typically pinkish or black, but if you look close, the individual pixels in the lines seem to be coloured arbitrarily. If the lines appear on a window, I can drag it around and the lines will follow. If I resize the window, the lines disappear.

Here's a screenshot. Note how the lines only affect the one window, and do not span the entire screen.
http://img161.imagevenue.com/img.php..._122_708lo.jpg

These lines aren't bound to a particular window, just the desktop as a whole.
http://img142.imagevenue.com/img.php...122_1119lo.jpg


Having reformatted, I feel it's a monitor or graphic card error. Apple ships hardware that can't last 2 years? Am I going to get shafted if I try to call them? Is there possibly a fix for this?

Thank you everyone for taking the time to read my post, and thanks in advance if you have some advice or want to express that you share the same issues.

12-28-2007, 04:00 PM

Have you picked up a trojan from some site?

12-28-2007, 05:56 PM

Originally Posted by harryb2448

Have you picked up a trojan from some site?

Alright, I'll make another post in case no one actually read my first one...


I zero'd my hard drive. I reformatted my computer. The lines showed up before I could start installing applications again.
I'm basically positive that NO software could cause this to happen.

Anybody familiar with Graphic cards? Could mine be fried?

Thank you.

12-28-2007, 06:27 PM

It appears as you have stated you are having a hardware issue. The graphics part of the logic board maybe going bad as you suggest. I don't think the graphics part is separtate from the logic board. You may have to replace the how thing.

Hopefully someone with a little more knowledge of the iMac will stop in and make things a little more clear.

12-28-2007, 07:06 PM

Originally Posted by rman

It appears as you have stated you are having a hardware issue. The graphics part of the logic board maybe going bad as you suggest. I don't think the graphics part is separtate from the logic board. You may have to replace the how thing.

Hopefully someone with a little more knowledge of the iMac will stop in and make things a little more clear.

Much appreciated.

I believe I have also heard that the graphics card is not separate.

If anybody else can even speculate what might be wrong, or if they can tell me if my assumptions/logic are full of crap, just about anything would be appreciated.

01-23-2009, 03:22 PM

Hey there TheNewFlesh, can I ask if you managed to get to the bottom of your issue - My Mac Pro has started to show exactly the same lines -

strange lines across my screen

Can you please let me know, if you have resolved this

01-23-2009, 03:39 PM

I just read the same thing on a prepress forum

Apple - Support - Discussions - 24" Imac Horizontal Video Lines Video ...

We have a White iMac but it is using Tiger also and we do not have the issue and it is now 2 1/2 years old. There is a thinking that Tiger/Leopard is overheating the graphics chip with the use of Quartz Extreme or something like this. One reader install the fan widget and increased the fan speed and it helped bring down the temperature.

01-29-2009, 09:57 PM

dont know how to fix that but i got the same problem with the same exact white imac.

01-30-2009, 04:38 AM

Originally Posted by watherton

Hey there TheNewFlesh, can I ask if you managed to get to the bottom of your issue - My Mac Pro has started to show exactly the same lines -

strange lines across my screen

Can you please let me know, if you have resolved this

It is the graphics card. If you have the ATI X1900XT in your MacPRo, as I have, you will find that many people, including me, have come across this when the card overheats due to dust on the card. For example, check out the comments in the Apple Store to the ATI X1900XT or google it and you will get loads of comments about this.

02-26-2009, 10:01 PM

Originally Posted by rogerinlondon

It is the graphics card. If you have the ATI X1900XT in your MacPRo, as I have, you will find that many people, including me, have come across this when the card overheats due to dust on the card. For example, check out the comments in the Apple Store to the ATI X1900XT or google it and you will get loads of comments about this.

Not I, said the guy with the nVidia 7300 GT.

Further more, if you think horizontal lines are bad - you should try playing World of Warcraft. Holy crap! Entire landscapes of strangely mapped polygons. Characters where polygons continue into infinity.

Strangest so far if you ask me; When I use Yahoo video chat, I'll get a green, static-pixelated bar across my video (self view) pane. Then the person I'm video chatting with me will comment, "Hey, there's a green bar across your video." YES! That's right. THEY CAN SEE MY VIDEO SCREWING UP!!! How freakin' weird is THAT?!?

02-26-2009, 11:43 PM

I'd agree, it sounds like something graphics related is happening to your computer.

If you have a 24" iMac then you can replace the graphics card by its self, unfortunately they are like $250 or so.

If you have a 20" then your stuck with on-board graphics, but sometimes this is still fixable.

Check and see if the issue is heat related . . . I know this sounds really strange but is it possible to put your whole iMac in your fridge and give it a shot. Be careful and don't leave it in there too long or use it excessively in there as it may cause condensation on your Logic Boar, rust, and cause archs between contacts.

The next thing to check is the capacitors. I think all white iMacs suffered from crappy capacitors (stolen electrolyte formula from Taiwan in the late 90s got taken to China and didn't end up so well).

Lemme know how it goes. . .

--Garrett

EDIT: NVM I don't understand what ancient post such as this surface. Sorry all.

03-16-2009, 01:26 PM

I have an ALU IMAC that exhibits the same problems.

Random horizontal lines.

Sometimes it broken up, other times it is a solid line.


When I re-log, it usually goes away...

03-28-2009, 06:18 PM

I am having the EXACT same problem with my white iMac

06-23-2009, 12:40 PM

I have this problem too, and it seems to be related to overheating. It's definitely something to do with the gfx card or logic board. The corruption is "logical" rather than physical, it can be copied & pasted etc, suggesting that garbage is getting into the graphics memory.

Could be temperature related, the GPU diode reads a good 10C hotter than the average of the other temp readings in my system. I don't know what the normal temps of the GPU are. Am going to find out how to dismantle my imac as I'm well out of warranty and see if cleaning all the air-ways & vents etc helps.

06-25-2009, 10:31 AM

I am having the same problem. I have a MacPro G5 tower running 10.5.7.

I have read everything from Graphics card and drivers to things from " revoved the prefpanes for APE, Dejavu, windowshade, little snitch and USB Overdrive"

It only occurs in a window not across the entire screen. It seems to happen more often when I have multiple windows open. Also, if in firefox I have a window open and it has the line going across it if I hit apple-n for a new window I usually get a window with out a line, but not always.

Any help is greatly appreciated! Thanks