1. You can not stand on what other PSU's do. There is no completely stable way of finding out a PSU is bad. On average, amp readings are much more reliable than volt reading.
2. No. That is not right. You say your board powers up and post, yet you have no display. You are going against yourself. You can not say it post if you don't get an image.
3. A bad supply does not mean that it is completely unable to power the system. You could be getting 150 watts on the 12v Rail. Would still power a board, RAM, and CPU, but be well beyond shot.
4. Test the PSU and see. Or as suggested and you agreed before. TAKE IT 2TO A SHOP!
1. For me, it makes sense that the Voltage varies when under different load, and I also heard it many times when I have been researching.
2. I'm not going against my words. I've always said the same mate, I get a short single beep, which indicates a succesfull POST according to my manual, however I get no display. I've always said that...
3.If it power's up the board, RAM and CPU, then what's stopping me from seeing video ? (I'm not using a GPU)Also, As I said, I just find it hard to be a PSU problem, as it has worked great until my first motherboard died. And worked fine when I had display.
4. I have been in touch with the only Local PC shop in my area, They told me they would charge me £30 to test my PSU, and when I asked how would they test it, all they told me was they have a specialised tester to test it. That too me is just a PSU tester. Now I'm not happy paying £30 for someone else to do exacly what I can do.