OK, socket was damaged, so obtained another m/b a Gigabyte Z370 HD3. So carefully put my original i7 6700 in mounted the board in the case, made all the connection. I turn it on and it comes on for a second and immediately shuts down. By disconnecting various peripherals it appears that the A1 power cable that plugs in just above the CPU is the culprit. When it is disconnected the PC runs for another 5sec before it shuts down. So I changed the power supply to a new 650 wattage now a Azersize Jans 650 W F-Power, this gives the same result. Given that the original PSU ran this set up before I assume it is not a lack of power. I also tried this with the i7 770k chip and the same result.
So could it be that both the processors were damaged when fitted to the damaged socket?
You can buy every Z370 motherboard on the market and you'll never get either your i7-6700 or i7-7700K to work on any of them for the simple reason that you cannot run Skylake or Kaby Lake processors on anything but 100 and 200 series motherboards. 300-series motherboards are completely incompatible.
Again, this is where doing homework is important. Just like you never, ever, ever update a BIOS unless you're using the exact correct BIOS, you never, ever, ever buy a motherboard without verifying CPU compatibility.
If you checked your motherboard's page (https://www.gigabyte.com/Motherboard/Z370-HD3-rev-10/support#support-cpu
), you would have found only Coffee Lake and Coffee Lake processors, as these were the only ones that ever worked, currently work, or ever will work with this motherboard or any other 300-series motherboard.