My 27 inch iMac failed, it has a bad mother board. The Apple service centre told me they can attempt to fix it but they did not believe their efforts were going to be successful. I opted to pull the HD, the memory and order a new iMac.
I will mail the 4 memory sims to anyone who wants them. They were purchased from OWC https://eshop.macsales.com/shop/memo...1/DDR3_21.5_27
in or around Nov. 2011. The product number on them is >OWC13333DDR3S4GB<.
Send me a PM if you are interested.