Motherboard, CPU, or PSU?

Question

Processors

Generally. Friends, such a story. PC crashed the other day. Everything turns on, it buzzes and makes noise, the indicators are on, they do not blink. Resetting the BIOS did not help, removing all the components too. Took it in for repair. All components are in order. Launched on another mother. I left my mother for repairs, took the hardware home, started everything on the old motherboard, sat for half a day - everything was covered with the same problem.
Mother first - ga-z77p-d3
Proc - e3 1280
Ozu 2x4g 1600
Video -1060 6g
Everything is new, except mother and processor, they are from China.
Old mother b75m d2v
PSU chiefteck eco 600w also new
What could be the matter?
Known solutions to such problems are northbridge, southbridge, and the processor socket.
But why were two motherboards bent?

Answer 1

Well, let's repeat the diagnostic procedure for a million second time:
Turn off everything in general, leaving only the motherboard and processor - turn it on - listen to beeping. There is no beeping - you can not continue, you need to check only 3 things, replacing them with known good ones.
There is a beep - insert one of the RAM sticks - turn it on - listen to the beep.
And then add one component at a time.