Apple IMAC User Manual - Page 103

Troubleshooting Symptom Charts/ Video Problems - 2 1 A predominant color tint or color covering the screen. 1 Verify that the iMac unit is not near other equipment (such as speakers, radios, phones, fluorescent lighting, magnets, or other electronic equipment) that could affect the video display. If necessary, move the iMac computer to another area and restart the unit. 2 Reseat the video cable connecting from the interconnect board to the main logic board. Make sure that both ends of the cable are firmly seated into their connectors. The interconnect board to logic board video cable routes behind the CD-ROM drive. If the connection to the interconnect board is not firmly seated, pushing on the CD-ROM drive can move the video cable enough to cause an intermittent connection. 3 Reseat the internal RGB cable at J5 on the A/V interconnect board and at P301 on the analog/video board. 4 Replace the analog/video board. Exhange like-for-like, there are two versions of this board. 5 Replace the internal RGB cable that runs between J5 on the A/V interconnect board and at P301 on the analog/video board. Erroneous text or characters appear on the screen 1 Boot off the system CD that came with the unit. Do you see a normal screen display now? Yes: Reinstall system software. (You must use the system software CD that came with the unit to get the correct version of Mac OS with the appropriate iMac enablers.) No: Go to next step. 2 Remove any VRAM DIMMs and restart the unit. Does the screen display appear normal now? Yes: Replace the existing VRAM DIMMs with known-good VRAM DIMMs. No: Go to next step. 3 Replace the logic board.