Apple IMAC User Manual - Page 100

Troubleshooting Symptom Charts/ Video Problems - 1 8 Yes: Replace the power supply to power filter cable. No: Go to next step. 7 Possible bad power supply board. Replace the power supply board. Video Problems No video, the screen is either completely black, or you will see horizontal rolling lines. There will be power to the system, however, which is evidenced by an illuminated amber LED, and a running fan. 1. Reset parameter RAM. Hold down during startup but before "Welcome to Macintosh" appears. 2 Reset the CUDA chip and try again. If the problem persists, reset the logic board. (See "The CUDA Chip" and "Resetting the Logic Board" earlier in this chapter for instructions.) 3 Do you hear a normal boot chime at startup? Yes: Go to next step. No: Follow these steps to resolve the problem: 1. Reseat the SDRAM. 2. Reseat the processor module. 3. Replace the processor module. 4. Replace the logic board. 4 Verify that the following cables are attached securely: • Internal RGB cable that attaches to the A/V interconnect board at J5. • Internal video cable that attaches to the logic board at J16 and the A/V interconnect board at J2. • Internal RGB cable that attaches to the video portion of the analog/video board at board at P301. 5 Replace the analog/video board. Exchange like-for-like, there are two versions of the board. 6 Replace the internal video cable that attaches to the logic board at J16 and the A/V interconnect board at J2. 7 Replace the A/V interconnect board. 8 Replace the logic board. 9 Replace the internal RGB cable that connects at the A/V interconnect board at J5 and the analog/video board at P301. 1 0 Replace the CRT.