HP A420n won't start after memory upgrade

[vahidm]

I added correct memory and after that the PC will not even power up. I did the basic trouble shooting. Remove the new memory. Swaped the meory around. Checked all the connection and incoming pwer, and checked the power out of Power supply. I do have 5V but no 12V.
PC only has soft start, so I don't know if the processor would tell the PS to turn on or not. Because nothing works, no fan, nothing. I removed the battery and drained the CMOS as well. Still nothing. The only thing I noticed is a blinking green light in the back of PS which used to be solid green when it would properly come on. I do get the solid green if I disconect it from the mother board.

Please help..... Thanks

[rokcwlr]

Check your main atx power plug into the MB. wiggle it allitleto see if the ps light goes solid.
Mine was bad, so i replaced MB and PS. Problem solved.