So i thought i would treat myself to a new GPU and i got the VTX3D AMD Radeon HD 7850. I put in into my pc and everything seemed ok i played a few games and was really impressed with the card.
Then I played Far Cry 3, here is were the fun begins. My psu went bang and wouldn't reboot. Luckily for me only the Kettle lead fuse had gone, But i changed the psu anyway just to be safe from a 500 to a 650 (also a new kettle lead)
It seemed fine again i played Dishonored, Bad company 2, and the Witcher 2. Then i decided to try Far cry again and the same thing happened it blew the fuse in my lead.
My pc was running fine before my new card, I just don't understand why it happens on Far cry 3 im guessing its just coincidence and it is the new card which is faulty.
Well, at least you know which game places the greatest demand on your PSU.
Your kettle lead is underrated for the application. The 650W PSU will require a 5 amp fuse for it's input, it sounds like you are fusing it with a 3 amp fuse. Ensure your kettle lead will accommodate 5amps capacity and re-fuse it. If it doesn't accommodate 5 amp fusing, buy one that does. The reason your fuses keep blowing is because of the current draw of your new GPU. You have all the protection you need built in to the PSU, you just need a more capable kettle lead.
DO NOT just put a larger fuse in your current kettle lead unless you have documentation on-hand stating that it can handle it. 5 amps (at 240Vac) on a 650 watt PSU should be adequate to the task, 3 amps, not so much.
BTW, as a general rule of thumb, the cheaper the PSU, the greater the input current requirements for a given output wattage (read: efficiency). There was probably no problem with your 500 watt PSU, but I hope you spent at least £70 on the new one.
If it was a 5A fuse that blew (5x230=~1150W, an 80% efficient 650W PSU shouldn't require more than 810 watts input ever) then I'd say you have an issue with the GPU. Especially if the machine plays well for any period of time prior to blowing.