My Emac moniter won't turn on, please help


So I've had my emac for almost 4 years and it started freezing along, which I'd id have to restart it to stop the freezing screen, It started showing symptoms of the classic grey screen issue but none of the ways to fix that worked and I took it to apple to have it looked at and they didn't know what was wrong, after they looked at it the screen stopped coming on, the computer works but the moniter (which is attached) won't show anything but black, its like the moniter is broken, please if anyone knows what to do or has had the same problem id really appreciate a reply :(
If you look at the serial number sticker, inside the CD door, you can see which eMac you have (the processor speed is listed there). I'm going to guess that you have a 1.25 GHz processor, which has had many problems with swelling capacitors. One of the symptoms of that problem is freezing, and loss of video - or video corruption. Sometimes, the eMac simply stops turning on at all.
Here's one thread (among many) that discusses that issue -
and how to check (open up the access panel on the bottom, and look inside.)
If you do see any swelling (or leaking) capacitors, the only fix is to replace the entire logic board, or find someone who can replace the bad capacitors, which should fix your problem. There are kits for the repair, but they rely on you having very good soldering skills.

Another report page about your issue: