When you say - No Signal. What you mean. Absolutely no lights, no fans spinning, no beeps, no Bios display, no Windows?
I don't want to give you false hope, or a false diagnose. The Q6600 was highly compatible so the fact you're saying it's not showing any life might be down to the chip itself. You've re-installed your old one successfully so we presume you know what your doing.
The first place to go and check is your motherboard manual and particularly the Supported CPU list, and the BIOS revision needed. It should be available on-line if you don't have the physical manual anymore. Assuming the board and the Bios are compatible with the chip then clearing the CMOS might bring it up. Particularly if you've moved any Bios setting from AUTO with your E2620.
So the Q6600 is working now? That's good news. Running Hot should be solvable. It's a matter of airflow, cooler and a good thermal paste seal. The last point is important if you've installed-removed-reinstalled-removed, and on and on. Put simply you should clean both the chip and heatsink before you apply new paste.
yes but it runs at 70 idle and 80-90 under load. which is not normal i already ordered a better cooler and thermal paste . i added an old r7 250(working perfectly) to this build and at random times the pc shuts down(.gaming or browsing) removing it solved the problem. (graphic drivers were updated). adding a gt 730silent or a 750ti doesn't cause this issue. the psu in this build is a cheap 450w no branding. why is the r7 shutting down?