Rebuild issue.

[Fossaw]

In the summer this year, I rebuilt one of my machines. It had a 2.4 GHz Core 2 processor. I rebuilt with a 4GHz i7, huge heatsink, on an ASUS Sabertooth, (their spelling), Z170 motherboard and 16GB RAM and a Corsair CX750 PSU. Case, SSD and other stuff remained. I was REALLY pleased with it, so much so, that I advanced my timescales and decided to rebuild my other machine this year as well. Exactly the same parts. It didn't start. I've just compared the spaghetti of twisted pairs between the two machines figuring a goof there, easy to do, but it seems okay. Now, of course, I can start swapping pieces between machines to see if I've got a dodgy part, but that is a real pain. Anything simple I can look at or try before going there?

[GReaper]

It doesn't start at all? Then it "must" be either the CPU, RAM sticks or motherboard. Start by taking the ram sticks out and replacing them one at a time. If that doesn't work, consider swapping the CPU.

Messing something up is easy. Double and triple check your wiring.

Check your MB's docs, it may tell you which diagnostic LEDs mean what.

If nothing works, then your PSU or your MB may be damaged/faulty.

[Mario F.]

Yeah, the Z170 has leds for almost anything. It even has an always ON green led that I came to understand it means that the coffee is ready.
Check the board during POST and the manual will tell you what's wrong.

[Fossaw]

It does absolutely NOTHING! No beeps, no clicks, no LEDs, no fans, nothing at all. The reason I checked the twisted pairs is I wondered if I had goofed the power switch connection, but it seems not. Mario, I'm guessing coffee isn't ready.

[Mario F.]

Damn right. Coffee's not ready. That would be the power input led (or somesuch) and if it doesn't even blink, I think you have a busted PSU... again!
It's extremely rare for even a broken motherboard to no react in any way. So I'd check the PSU first.
Get the good PSU from the other machine and test with that.

EDIT: And I have never met anyone so unlucky as you.

[Fossaw]

My wife is nagging me to get ready to go to her sisters place for Christmas, so I'll have to put what I want to do on hold until we get back, but I'll start there, the PSU is not the worst thing to swap. Bad luck has been a constant companion since 2008.

[Fossaw]

I survived my sister-in-laws place, which went very well actually. Back here and to the PSU swap. Stripped both out, put the known good unit in the non functioning machine and the unit from the prviously non functional machine in here. All cabled up and this machine starts without a problem, (actually one minor problem - I'd put the speaker jack in the mic socket and the mic in the speaker socket hey, it's dark), but it started crunching BOINC tasks as it had been earlier today. The previously non working machine also started without issue. So, a result. A little puzzling though, the power cables have clips on them which click into place and are fiddly to remove - all were fiddly on both systems. It surprises me a little that they can click in, and yet fail to make a good contact, but there you go.

[Fossaw]

It still is not running. Curious that. All is the same as the working system, yet when starting up, the BIOS says there is a problem with the CPU fan. The CPU fan is, I assume, the fan on the heatsink, it is there, and it is spinning. It is connected to the same power pins as the heatsink fan on this machine, yet stubbornly refuses to accept the fact. The only fan difference I have is that this machine has an exhaust fan on the back of the case which the other does not, I would not expect that to be the issue though. The motherboard manual does not identify a specific set of pins for the heatsink fan.