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Bought a used iMac A1311 without a display screen. It was tested before I bought it and was released by an apple tech as it functions as intended. Bought a screen and installed it. Turned it on and got 3 beeps. Checked and fixed the RAM and tried again. This time got the Apple chime could here it booting but screen was black. Also replaced cable #593-1280 A. Double checked everything still a black screen. Haven’t tried an external display yet, had to order a Mini DisplayPort adapter. In the meantime any ideas what I can try while I’m waiting for this adapter. Any help will be appreciated. Thank you Lynn Your other posting: Bought this iMac used from a reputable seller of macs. He tests everything he sells. All it needed was the screen which I bought separately, also replaced the main cable 593-1280A. I did have trouble plugging it into the logic board, tight squeeze! But the vertical sync cable won’t connect where it’s supposed to go. One Mac has a plug in cable and the other has a ribbon connection. The ribbon looks damaged could this be it?
@lynnwood53 either you identified your iMac incorrectly or you do have the wrong parts. The attached image will show you the proper part numbers for your iMac if is it indeed a Mid 2010. You do want to go ahead and verify that. You also want to let us know which panel part number you bought so we can verify that for you. It does sound like you have the wrong parts.
Update (12/13/2018) @lynnwood53 your iMac is a “Core i3” 3.06 21.5-Inch (Mid-2010). The panel for that is a LM215WF3 (SD) (A1) Apple part number 661-5536. The panel you have is a LM215WF3(SL)(A1) which is Apple part number 661-5303 and is for a iMac 21.5" Late 2009. They are NOT compatible. The connections on CN1 are wired totally different. That V-sync cable helps the larger displays to stay,well in sync. Without it you would hear a high-pitched whine from the display and there will be flickering, harmonic vibration in the image.It forces the images displayed to be shown as a whole.
First restart your system in a darkened room, do you see any glow from the screen? If you do, try placing a flashlight on the screen at a sharp angle you should be able to see the faint image of desktop icons and background. If you don’t see the glow but do see the screen image with the flashlight then the backlight circuit needs repairs. If you do see the glow but don’t see the screen image either the LVDS display cable needs replacing or the GPU logic need repairs. Does the external display work once you get the adapter?
