Apple IMAC User Manual - Page 112

Troubleshooting Symptom Charts/ Sound Out Problems - 3 0 Sound Out Problems No sound coming from the internal speakers, external speakers (connected via the I/O panel to the speaker connector on the logic board), or both. 1 First, disconnect any external microphones, speakers or headphones. Next, verify that volume setting in Control Panel is adequate and that mute is not checked. Test the for sound coming from the internal speakers. Do you have sound now? Yes: If the initial sound out problem was with the internal speakers, the problem is solved. If you reconnect the external sound out device and it is not working, the problem may be with the external device itself or its cable. Replace the external microphone, speaker, or headphone in question with a known-good device. If the problem persists, replace the logic board. No: Go to next step. 2 Reset parameter RAM. Hold down during startup until "Welcome to Macintosh" appears. 3 Verify that both ends of the internal speaker cables are attached securely. 4 Reseat/replace the audio cable going from the A/V interconnect board to the main logic board. Make sure both ends of the cable are firmly seated into their connectors. 5 Reseat/replace the audio cable (922-3624 or 922-3836, Rev. 2) at the A/V interconnect board and the power/ headphone board (922-3568). 6 Plug known-good headphones or external speakers into the external jack. Do you get sound? Yes: Go to next step. No: Replace the logic board. 7 Replace the A/V interconnect board. 8 Replace the power/headphone board. 9 Replace the logic board.