Replaced CPU with i7 - now 1 LED blinking

Hi,

Model: iMac "Core i5" 2.7 27-Inch (Mid-2011)

I replaced the i5 CPU with an i7 2600. But on boot I got a blinking single LED on LED1. Reading up that normally means insufficient power.

The main fan would spin cycle up and down.

I put the i5 back in and it boots fine.

Things I'm not sure about:

• I'm assuming the CPU is good, but can't be 100% sure
• I didn't put the RAM back in when I tested the i7, but normally you'd get a long tone.

Anything else I can try?

I'll have another go when I've got more time and double check I've seated all the cable correctly etc...

Big shame if it doesn't work - I was looking forward to the upgrade :-(

Thanks!