No Power on Gigabyte Motherboard GA-Z77X-UD5H

Hi All

I managed to build my system last week which is:


- Corsair 800W PSU Gaming Series (originally Corsair 750 W Enthusiast Series)
- Antec P280 Case (size, air flow, sound proofing, wiring)
- Gigabyte Motherboard - GA-Z77X-UD5H
- CPU Processor: Intel Core i7-3770k
- Corsair Vengeance Ram - 8 GB X 4 (32 GB Total and maximum for this motherboard)
- SanDisk Solid State Drive (main boot) - 240 GB
- Seagate 3TB internal drive
- Asus GEFORCE GTX 660Ti 2 GB Nvidia Graphics Card
- Samsung 27" Monitor with internal speakers (S27B55VS)
- Logitech K120 Keyboard
- Logitech G400 Gaming Mouse


However on Friday, installing Mac OS and Windows 7 Home edition (plus updates) all seemed to go well untill I then shut down the system and then restarted or tried to re-power the system.


For some reason there was no active power on the motherboard, usually the internal power up switch next to the LED Debug Code display area on the GA-Z77X-UD5H is red however there was no red light on.


I assumed the fault was with the power supply unit and tested this I tested the power supply using a PC/SPS Tester and seem to getting green lights where i expect. However I did notice that for the 24 pin adapter which when plugged into the tester activates the power to the case so the fans work but the readings were green for:


+3.3V
-12V
PG
+5SB
+12V
+5V


However I notice there is no reading for -5V and wondered if this was the cause of the problem.


I could not find any documentation which would tell me what actual power was required by the mother board from the 24 pins please can anyone advise on this problem - ty.


Regards,


Graham