All diagnostic leds on S2600CO4 light up when I turn on the PSU. The 5 V Standby led is GREEN though while the others -- ORANGE. After switching the PSU off and on the ORANGE leds go off and SYS_STATUS (A) fires up (GREEN). I'm at a loss here -- I don't know if it's a typical behaviour as I've never seen a healthy S2600CO Series -- what could be wrong with it?
Besides, when I turn the power on nothing happens or, rather, nothing of importance for over 3 minutes whether it's a cold or hot start -- fans start spinning, CPU warms up, but no leds (barring 5 V Standby), no beeps, no video output.
CPU - Xeon QB79 E5-2680
RAM - HP-branded Hynix 4GB 2Rx4 PC3-10600R-9-10-E1
PSU - Zippy P1H-6400P (400W)
A few things to try: just use a single processor and DIMM, if you currently have more than one installed. if that doesn't work, pull all memory, see if you can get the board to power up and give you three beeps. If it does, you have sufficient power for the processor(s) at least. The power supply should be capable of outputting 24 amps on the 12V rail, peaking up to 28A on boot, potentially.