820-01069-b board with no display after upgrading the RAM.

[Estee]

Good morning to you all.

I have same 820-01069-b board with no display after upgrading the RAM.
Removed the new RAM and put back Original RAM, No Display.
SMC and PRAM reset also no help.
Not connecting to External monitor also.
LED 1, 2, 3 ok. But the 4th LED not coming up.
No Apple chime.
The display is working well with another imac.
Nothing wrong with both power and display cables.
What could be wrong?

[reformatt]

What year is this? If the 4th LED isn't coming up, it means it's not communicating with the display. I've had some display cables go faulty on me on some of the old ones. You might need to seat the cable a few times to get the display to come up. Can be the connector is faulty or the fuse is blown for the backlight.

See if it's booting first by running the board with a chipmunk USB tester. Green LED should flash if the port is being probed.