HI All，I have an IMac 27''(A1312). Several days ago, I left it with sleep, and yesterday I pulled the cord out. Then the machine won't start up anymore. It doesn't have any chime or HDD start voice. I checked the forum and tried reset the SMC and RAM and even switched a plug, but it still doesn't work. Could anybody give me some advice on this? Since apple said it won't under warranty anymore for I add a SSD to my Imac last year.Thank you in advance.