Apple imac 20 inch early 2008 User Manual

iMac (20-inch Early 2008) 
  —  Sym pt om   Char t s    2 41
No Video, Boot Chime Heard
The computer will turn on, the boot chime is heard and fan or drive activity can be heard, but the 
display has no picture or color.  
1. Make sure all software updates have been applied to the computer.
2. Check if the computer is sleeping. Press the space bar to wake the computer from sleep mode. 
Did the computer wake from sleep?
Yes: Put the computer to sleep from the Apple menu and wake the computer again to...

iMac (20-inch Early 2008)  — Symptom Charts  242
completely black, or can you see a dim light or purple glow to the display? 
Completely black: Replace the inverter.
Dim light or purple glow: The inverter and panel backlights are functioning. Replace the 
LCD display panel.
LED # 4 is Off: The video card and logic board are unable to communicate to generate video. 
Replace the video card.
Display is tinted another color
The iMac computer has a tinted glass panel covering the display, giving it a new look...

iMac (20-inch Early 2008)  — Symptom Charts  243
When displaying a single color over the screen area, the LCD panel shows one or 
more pixels that are not properly lit.
Active-matrix LCD technology uses rows and columns of addressable locations (pixels) that 
render text and images on screen. Each pixel location has three separate subpixels (red, green, 
and blue) that allow the image to be rendered in full color. Each subpixel has a corresponding 
transistor responsible for turning the subpixel on or...

iMac (20-inch Early 2008)  — Symptom Charts  244
Hard Drive
Flashing question mark, or an alternating question mark and Mac OS (face or a 
folder)
Note: When troubleshooting hard drive problems it is a good idea, if possible, to back up any 
important data. Some troubleshooting steps may require erasing the contents of the hard drive.
Boot from the system CD that came with the computer, and open Disk Utility. Does the hard 
1. 
drive show in Disk Utility? 
Yes: Run Repair Disk and Repair Permissions to...

iMac (20-inch Early 2008)  — Symptom Charts  245
Hard Drive Information
Note: The following information is for Intel-based and PPC Macintosh drive compatibility
Drives to be used in booting Intel-based Macintosh hardware should be formatted and 
• 
partitioned with an Intel-based Macintosh disk utility running on Intel-based Macintosh 
hardware. That should ensure you get the correct default partition map and structure for 
reliable booting.
Intel-based Macintosh CPUs in Target Disc Mode will only mount...

iMac (20-inch Early 2008)  — Symptom Charts  246
Optical Drive 
Optical drive won’t eject media
Carefully remove the EMI tape on the top of the optical drive.  1. 
Caution: The optical mechanism is VERY delicate and should be handled with care. Handle 
the drive by the sides and the back edge. Avoid touching the front of the drive and putting 
pressure on the top and bottom cover. 
Verify that two or three black clips (as shown below) are positioned on top of the optical 2.  
drive mechanism. Note:  The...

iMac (20-inch Early 2008) 
 — Symptom Charts 
 247
Remove the optical drive. Look at the optical drive from the front. Inspect the carrier 3. 
opening, make sure it’s even all the way across. If a clip is caught under the optical 
mechanism, the optical drive mechanism will be bowed or warped. Is the mechanism bowed 
or warped?  
Yes: Remove the four T8 shoulder screws on the carrier. Reseat the carrier so the black clips 
are visible on top of the optical mechanism. Test the optical drive. If the...

iMac (20-inch Early 2008)  — Symptom Charts  248
Replace the optical drive.
9. 
Replace the logic board10.
  

iMac (20-inch Early 2008) 
 — Symptom Charts 
 249
CDs or DVDs don’t show up on the Desktop
Select Preferences from the Finder menu and make sure the option to show CDs, DVDs and 1.  
iPods is checked: in the General window as shown below.   

iMac (20-inch Early 2008)  — Symptom Charts  250
Select System Preferences from the Apple menu and open the CDs & DVDs preferences 
2.
 
window. Make sure that audio CDs are set to launch iTunes and movie DVDs set to launch 
DVD Player when those media are inserted, as shown below.  
Check that the drive can read discs normally. Insert an audio CD and check whether it shows 3. 
up on your desktop or launches iTunes.  
Does the audio CD mount on the desktop or in iTunes? 
Yes: The drive seems to read CD...