The iMac display has no video. The computer has a startup sound, the LED is on, and the hard drive starts up.

This article covers repair procedures for authorized service providers on selected Apple products, but we have published them in the Knowledge Base for the general public for educational purposes. At this time, there are a limited number of repairs that a customer can perform and these are covered under the customer installable parts program http://www.info.apple.com/installparts . If you have not been authorized to perform these procedures, please contact Apple (800-APL-CARE in the USA) or your local authorized service provider to schedule a repair.

DANGER! This procedure exposes you to high voltages that can result in death or serious injury. DO NOT ATTEMPT THIS PROCEDURE IF YOU HAVE NOT BEEN CERTIFIED AS AN APPLE-AUTHORIZED TECHNICIAN.

Symptom

The iMac display has no video.

Products affected

• iMac (Slot-Loading)
• iMac (Summer 2000)
• iMac (Early 2001)

Solution

1. Reset parameter RAM. Press Command-Option-P-R during startup before "Welcome to Macintosh" appears.

2. The system software could be damaged. Start up from the system CD that came with the computer. 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.
No : Go to next step.

3. Press the PMU chip on the logic board with the AC power cord disconnected. For more information on resetting the PMU chip, refer to article 95002: " Resetting the Power Management Unit (PMU) on the Logic Board ".

4. Verify that the video board cables, the RGB video cable, and P701 (the deflection yoke cable on the power/analog board) are attached securely. Refer to article 31263 :" iMac (Summer 2000): Troubleshooting the Power/Analog/Video Board" for additional information. If the problem persists, go on to the next step.

5. Remove the CRT video board. Check that the pins on the CRT neck are not bent. Carefully reseat the CRT video board and power on the computer. Do you get video now?
Yes : Run MacTest Pro diagnostics and return the computer to the customer.
No : Go on to the next step.

6. Check for trickle power on the logic board. Refer to article 95001: " iMac: Testing for Power on the Logic Board" . Trickle power is present as soon as the power cord is plugged into the computer. Did you measure +5 V trickle power on pin 1 of connector J9?
Yes : Go to the next step.
No : Refer to article 95003: " iMac: No Power ".

7. Check for DCO voltage at location C10 on the logic board. Refer to article 95004: " iMac: Testing for DCO (Down Converter On) Voltage at C10 on the Logic Board ". Did you measure approximately -1.2 volts?
Yes : Go to the next step.
No : Replace the logic board.

8. Replace the internal RGB video cable that attaches to the power/analog/video board and to the logic board. The cable is screwed to the divider panel, and is located near the AC power plug on the power/analog board. If replacing the RGB video cable does not solve the issue, go on to the next step.

9. Replace the power/analog/video board.

10. Replace the CRT.