Following clocker's recent puzzle, I got another for some of you to try to figure out.
I'm building a new system for my brother, he only wants it for internet/business so no fancy graphics required.
So I got him a Biostar 6100/M9 motherboard, Athlon64 3200+, 1GB Corsair VS cas2.5 memory, 80GB Maxtor Sata drive, NEC 3550 DVD writer, Cheap aluminium case (but seems well designed), Akasa Paxpower 400W PSU (Which I believe is a rebadged Seasonic S12-430).
I initially put the processor, memory, motherboard and PSU together to bench test these components. All the fans powered up but it wouldn't post. I took my own system apart and substituted the cpu and memory, both were fine. Next I tried the PSU in my system, that too was fine, so the only thing left was the motherboard. I quickly checked that the DVD writer and HDD were ok, and headed back to my supplier with the motherboard.
Of course it is Saturday morning, and they've only got a skeleton staff working in technical support (most of their business if Mail Order, Mon to Fri), so their stated policy is book it in and leave it for testing. However, I know from experience that if it is easy to diagnose they will often test it while you wait. I'm lucky, they aren't too busy. They test it and it works perfectly.
I take it back home, plug it together again, it doesn't work. However, I've seen it working (with their cpu and memory). So I put the cpu and memory from my own system in, it still doesn't work. I remembered at this point that they had been using a PSU with a 20 pin plug, so I get out the cheap and nasty PSU that came with the case, plug it in, and straight away the system posts.
The puzzle for you to work out is why it posts with the cheap PSU, but not an expensive one. I warn you, I hadn't actually done anything wrong, so it's going to be a little harder to work out than clocker's problem.