Avatar of 1namyln
1namylnFlag for United States of America asked on

Video issues with iMac 20"

I have a client whom has a 20" iMac running 10.6.8 with 2.16 C2D CPU.  The problem they've been experiencing is sometimes there will be a diagonal line in the screen that just appears and it will not go away until the system is restarted.  When playing Hulu and other video the video will sometimes freeze and the sound will continue.  Shortly there after the sound stops and the entire machines freezes.  Only way to correct this is to hold the power button down and then turn it back on.

I've had the machine for a day now and have not been able to recreate these issues.  I've tested it with the Mac diagnostic mode by holding the D key while booting.  The short and extended test finish with no issues.  

I have a hunch these issues are related to the video card but I don't know how to stress the card in a Mac.  First thing I've done is remove all dust from the machine.  Thanks in advance.
Apple HardwareApple SoftwareApple OS

Avatar of undefined
Last Comment

8/22/2022 - Mon

I also test the memory using UBCD.  Found no issues.
Eoin OSullivan

Log in or sign up to see answer
Become an EE member today7-DAY FREE TRIAL
Members can start a 7-Day Free trial then enjoy unlimited access to the platform
Sign up - Free for 7 days
Learn why we charge membership fees
We get it - no one likes a content blocker. Take one extra minute and find out why we block content.
See how we're fighting big data
Not exactly the question you had in mind?
Sign up for an EE membership and get your own personalized solution. With an EE membership, you can ask unlimited troubleshooting, research, or opinion questions.
ask a question

The Mac came with a hardware test on the install CD. See:  http://support.apple.com/kb/HT1509

Run the hardware test.

Isn't that the same test I spoke about in my original post or is this a different type of test?  Any idea if this video card is replaceable without having to replace the entire logic board?
Experts Exchange has (a) saved my job multiple times, (b) saved me hours, days, and even weeks of work, and often (c) makes me look like a superhero! This place is MAGIC!
Walt Forbes

Right. I missed that. Sorry.
Davis McCarn

That iMac has an MXM ( http://www.mxm-upgrade.com/types.html ) video card which means it can be replaced; but, I need to know the part number of the iMac: http://support.apple.com/kb/HT1758
The x1600 cards is notorious for overheating and subsequently failing.  If you are lucky, we'll be able to upgrade it in the process.

Run one of the many available stress testing applications, and stream an endless loop of youtube videos in a couple browser tabs  (endlessvideo.com).  

Based on the model and symptoms you describe, I concur with everyone else that you likely have a video card issue.  I've seen more video card issues in the 20" iMac than any other model.    I recommend getting the exact same card, rather than trying to upgrade to a different model.. it wouldn't help you much to eliminate one issue, but then get a kernel panic or something else. ;-)

Good luck
Get an unlimited membership to EE for less than $4 a week.
Unlimited question asking, solutions, articles and more.

I'm not sure how to tell which version iMac 20" this is but I've pasted the more info about this Mac below.

  Model Name:      iMac
  Model Identifier:      iMac5,1
  Processor Name:      Intel Core 2 Duo
  Processor Speed:      2.16 GHz
  Number Of Processors:      1
  Total Number Of Cores:      2
  L2 Cache:      4 MB
  Memory:      3 GB
  Bus Speed:      667 MHz
  Boot ROM Version:      IM51.0090.B09
  SMC Version (system):      1.9f4
  Serial Number (system):      QP7010V4VUV
  Hardware UUID:      00000000-0000-1000-8000-0017F2CE229A

ATI Radeon X1600:

  Chipset Model:      ATY,RadeonX1600
  Type:      GPU
  Bus:      PCIe
  PCIe Lane Width:      x16
  VRAM (Total):      128 MB
  Vendor:      ATI (0x1002)
  Device ID:      0x71c5
  Revision ID:      0x0000
  ROM Revision:      113-xxxxxx-139
  EFI Driver Version:      01.00.139
  Resolution:      1680 x 1050
  Pixel Depth:      32-Bit Color (ARGB8888)
  Main Display:      Yes
  Mirror:      Off
  Online:      Yes
  Built-In:      Yes
Display Connector:
  Status:      No Display Connected

I will try the endless stream.  I've tried looping dual and more 1080p within YouTube and have yet to be able to recreate this since I've had it in my shop.

Sometimes it can take a while to reproduce.  

Type the serial number into this Apple site, and it will tell you what model you have:


Looks like a Late 2006, based on the information you pasted.
All of life is about relationships, and EE has made a viirtual community a real community. It lifts everyone's boat
William Peck
Log in to continue reading
Log In
Sign up - Free for 7 days
Get an unlimited membership to EE for less than $4 a week.
Unlimited question asking, solutions, articles and more.

I've recreated one of the issues.  I get a line in the video.  If I minimize the video the line isn't in the screen.  If I bring the video back up I can see the line again.  If I change the video to full screen the line goes away.  I've yet to get the machine to lock up fully.  Trying endlessvideo using high HD video.  Ran both xbench and novabench.  The system finishes the test with no issues I can see.

If I play a game like reversi, I can see the video from behind flicker occasionally through the game I'm playing.  It flashes very quickly.
Davis McCarn

Ther isn't much you can do with bad hardware except to replace it!
Get an unlimited membership to EE for less than $4 a week.
Unlimited question asking, solutions, articles and more.

Understood.  I was just trying to verify these issues were video card related.  In the past when I've experienced lines, dead pixels, etc. they stay on the screen.  This one is different so I was hesitating before coming to the conclusion the video was faulty.  This is only my 5th Mac repairing.

From what I'm reading this is common.  That being said, I don't think I can recommend replacing the logic board with good conscience as the new board may have the same issues at some point, correct?
Davis McCarn

The user must be hypervigilant about keepin the cooling fans free from dust!  If you got very little out of your cleaning process; then, yup, it ain't worth repairing.  If it was quite dusty, then the replacement might be worth the cost.
This is the best money I have ever spent. I cannot not tell you how many times these folks have saved my bacon. I learn so much from the contributors.

Do you have an opinion about this program  http://www.macupdate.com/app/mac/23049/smcfancontrol and its ability to help my problem?
Davis McCarn

It may delay the inevitable; but, you either have silicon which is damaged or a part which needs reballing.

Late 2006 system might be worth $500 maximum if everything was working perfectly.  It's likely uneconomical to replace the logic board.. but  I would let the owner of the system make the call.  Like Davis said earlier, with bad hardware you just replace it most of the time.  If the damage has already been done, manipulating the fans will not help much.
Get an unlimited membership to EE for less than $4 a week.
Unlimited question asking, solutions, articles and more.