Computer with recently RMA'ed parts won't POST. Worked 2 days prior

[Asics]

Hi guys, I'm having trouble with a computer I built. Sorry for the long post but I've tried numerous troubleshooting steps, RMA'ed multiple components, and am at my wits end about it.

Tl;dr computer won’t POST, worked two days prior with same setup. Recently warranty returned power supply and motherboard. Skip to the last paragraph for the most recent update.

Build – https://pcpartpicker.com/list/CgffGf (Links to an external site.)

I built a computer in November 2016 and it worked well until the end of December 2016. On New Year’s Day, I found it powered on with a black screen that was unresponsive to input so I turned it off by holding the power button. I waited a minute to try turning it back on but it wouldn’t respond. I tried a few more times and found that about 9 times out of 10 the power button didn’t do anything. The other 1 time, the computer would receive power for a split second and then turn back off. The symptoms sounded like a power supply problem so I warranty returned it. This power supply is different than the one listed in the build: the original one was a Corsair CXM650.

The RMA was being delayed so I requested a similar model to expedite the process to which Corsair agreed: they changed my PSU to a Corsair RMx650. While waiting, I tested my computer with a different and known working power supply; an EVGA 430w model. It produced the same symptoms so I requested a warranty return with the motherboard manufacturer.

When the new power supply and what I assume was either a repaired or replaced motherboard came in (ASUS didn't say), I “breadboarded” the components one at a time and used the motherboard LEDs to judge if the computer could detect the components. I don’t have a speaker to listen for POST error codes. Each worked so I assembled the components inside the case. I could boot into Windows. While using the computer, I could use programs including a hardware monitor (Speccy) that said only 1 of 2 RAM modules were detected. I was not able to test the graphics card. Temperatures were normal and the computer seemed to be operating normally.

A couple of days later I attempted to turn the computer on. When the power button was pressed the machine sounded like it was turned on with all fans spinning but there was no display. I turned it off and opened the case and tried again. The MemOK! LED was lit and not blinking, possibly a RAM problem? I tried every combination of RAM: no RAM and then each stick tried in each slot. I tried plugging the HDMI into the motherboard, tried removing the graphics card, resetting the CMOS battery (which produces its own separate symptom: on a cold boot the machine will power up for a second, power down, then power back up and become stable). I tried pressing the MemOK! Button next to its LED; it resets the machine and produces the same symptoms but the MemOK! LED is lit and blinking. The blinking starts slowly but gradually changes to a faster blink. When the memory LED changes speeds, the CPU LED flashes, unsure if related but relevant.

Worth noting that both the warranty returns were accepted, does that imply that both were defective? If so, what other problems could arise from a faulty PSU and motherboard?

[moremana]

Take the cpu out and look real carefully at it..seriously.

[Asics]

Take the cpu out and look real carefully at it..seriously.

Looking for bent pins? I consulted the photos I took when I received my motherboard and I didn't see any bent pins. Also I don't think I bent any myself but its worth a look.

Does the fact I was able to use the computer a few days prior to it not being able to POST matter at all?

[Akainakali]

Does the fact I was able to use the computer a few days prior to it not being able to POST matter at all?

It's impossible to say if that matters or not.

It's entirely possible for a bad PSU to kill a MB or that some sort of a powersurge that fried the PSU to also damage the motherboard. Likewise something that caused issues with the PSU and MB, could also easily damage the CPU or memory.

It's always handy to have a known "good" set of components you can swap stuff into, but that can get expensive quickly for obvious reasons.

I assume you've turned off all overclocking of any sort for any of the components?

I would google to see if your motherboard has any quirks. My motherboard is fairly old and in general I don't think this is the case for most current motherboards, but you did have to make some non-obvious changes to settings to be able to use a lot of common ram on it.