Delta 400w psuWhat's the make and exact MODEL of your PSU ? How old is the GPU ? Are you on Windows 10 OS ?
Delta 400w psu
while i am using pc it starts showing blue red checker(small cubes)
Average temp is 86CThe thing is that buying used GPU can go good way or a bad way but looks like you been sold an GPU that has artifacts or it could be that the gpu is overheating so check the temps
How can i test gpu properly