Here are the following steps you will need. Let me know if there is anything else i can help with. The glass panel is held in place by magnets in the rear housing. So follow these steps:
- Lay display on its back and press clean suction cups in opposite corners on glass panel. I strongly recommends wearing clean, lint-free gloves whenever handling the glass panel, to reduce cleaning required on reassembly.
- Lift Glass panel straight up and off.
- Remove suction cups and slide glass into protective microfoam bag
- Remove 6 T10 screws: 3 on each side of the LCD panel.
- Raise bottom edge of LCD a few inches using black mylar tabs.
Careful! There are 4 cables to disconnect.
From Left to right:
- Cable 1. Ambient Temp Sensor
- Cable 2. AIO Video
- Cable 3. LCD Function Interface
- Cable 4. LED Driver (Backlight)
- Lift LCD panel straight up and off.
Disconnect power supply cable from logic board. Verify cable voltage at connector between Pin 1 and chassis ground (GND) is 14.3–15.8 VDC. No power or incorrect power to logic board. Most likely:Replace power supply. If the power checks out do the following steps..
Disconnect all connectors from the logic board EXCEPT the power supply cable. Verify voltages on logic board between test points TP61 (3.3VDC) and chassis ground (GND) is 3.1–3.5 VDC, and between TP13 (12VDC) and chassis ground (GND) is 11.4–12.6 VDC. IfPower supply OK.
Suspect possible short, damaged connector, or faulty sensor/ fan/speaker. Reconnect connectors one at a time and retest for 3.3VDC at TP61 and 12VDC at TP13. Replace affected part that causes the 3.3VDC or 12VDC voltages to disappear. If everything checks out ok, Replace logic board.
here is the link to go with the steps. It will have a pic of the logic board and spots to check.
Thanks for your detailed info and picture responding to the ACD LED 24" question on the ifixit board.
I'm in a similar situation. I was given a 24" that wouldn't display anything. I'm able to plug the display in and get the speakers to work, charges macbook, camera works, USB works . . . but no image - blackness.
When I go into the display preferences it doesn't recognize the display. So . . . I followed your handy steps and took the beast apart for some testing. I was able to verify 14.7 VDC from the power supply.
Then I disconnected everything but the power connector to the Logic board and was able to verify all of the correct voltages (per your brilliant share of the photo/info). I reconnected everything one by one and still verified correct voltages. The only thing I didn't reconnect/check were the connections going to the LED display - "Cable1. Ambient Temp Sensor,Cable2. AIO Video,Cable3. LCD Function Interface,Cable
I reconnected LED just to double check if it was a loose connector - still no love.
If I'm reading your directions correctly - this would seem to indicate it's time to replace the logic board - yeah? Is there anyway to test the LED? Or should I just bite the bullet and order a new logic board?
Thanks so much for taking the time to post and respond. Any insight/tips would be greatly appreciated.
Ifixit sells the suction cups required to repair but they aren't listed on the right hand side.... Hopefully they add it...
Two 2.25" diameter suction cups used for lifting display glass off Aluminum iMacs. A must-have tool when repairing or replacing broken, cracked, or shattered iMac screens. — 50+ available at 14.95 each.