iMac won't start after installing SSD and dust cleaning

@lemerise - The display panel was removed, so, LVDS was not connected there. However, I did remove the hard drive connection from the logic board (both SSD and regular 3.5” hard drive connection, just left the optical drive connection there), but issue is the same, any thoughts?

would you try to let the two drives disconnected and just connect the screen and try to start the machine ? I'm not a iMac specialist but maybe the machine need to see a screen connection to fully start. If it start then the hard drive/SSD connections would have to be investigated.

@lemerise - Here is the update, I removed the logic board from the shell case and did the connection again, and found the followings:

1. Connect nothing at SATA 0 through 2, LED 2 is stable and booting continues.

2. Connect only optical drive at SATA 2, leave SATA 0 and 1 open (without any hard drives), same as #1 above.

3. Connect optical drive and one hard drive (either at SATA 0 or 1), LED 2 can stay with LED 3 lights up for about 10 or 15 seconds, then both LED 2 and 3 turned off, and continue this loop.

4. I physically check the SATA 0 and 1 connectors on logic board, they look fine to me. The SATA and power cables are OK (as it was tested on one of my other iMac desktop).

So, can I conclude that something is wrong with SATA 0 or 1 connectors at logic board itself? Any thoughts?

Thanks,

Did you try to start up the system via USB with an external drive (both internal drives disconnected) or with the installation disk that came with the iMac ? If it boot OK then you can investigate your drives and the internals connections. Also reseat your ram sticks just in case.