Issue Asus Z97 model of motherboard -

[Addiepower]

Hi, originally had an Asus Z97 Pro Wi-fi AC motherboard - 650W PSU, Intel Core i7 4790T CPU, 4x 8BG Kingston DDR3 1333 Ram.  Was working in the morning and when returned home went to use PC, which was still running but screen blank like it was hibernating.  No response so restarted it. 

It then would start to boot for around 0.5s, then switch off for 2 secs, try and restart for 0.5s switch off for 2secs. and continue this cycle.  Knowing this was either PSU, Motherboard or Memory I tested PSU by crossing the two pins on the main 24 pin ATX cable which started the fan on the unit but it wouldn't remain running when I removed the paperclip from the 2 pins.  I replaced the PSU.  This didn't fix the issue. 

I then isolated the issue to the extra 8 pin EATX12V connector to MB. That is, the PSU would fire up if I only had the 24 pin connector on MB, but it would cycle on and off if I also had the additional 8 pin connected (in manual says this is mandatory or else system won't boot up).   After looking again online found that this seems to be an issue with these MB (from Reddit) due to a chip (No29) failing after some years.   

MB is the issue. Found similar model online which was cost effective Asus Z97 - AR model.  It arrived new (they must have some left-over end-of-life stock in China) without a CMOS battery.  No problem I used my old battery. Connected everything up and now it all switches on but won't get to the POST screen, and the DRAM LED stays LIT.  There was no issue with the RAM on my original model and looking at the manuals of both models the wording around which RAM to use is identical.  I checked the RAM, cleaned it, tried each stick separatley etc and no luck.

So, as it happens, I had a backup CPU from a year prior,  as there was an issue with my CPU back then.  Before this new CPU arrived, I was playing around reseating it and practicing putting the thermal paste on it etc and all of a sudden the old CPU worked again.  So I have this backup CPU unused.  This gave me the luxury of replacing the CPU.  This STILL hasn't fixed the issue of me not getting any signal out of the PC.  I am using the onboard HDMI output at the moment, even though I also have a dedicated graphics card, but won't install these peripherals until I get a POST signal at the very least.  CAN ANYONE OFFER ME ANY HELP HERE, besides bite the bullet and buy a brand new latest MB, CPU and new RAM.   I really cannot afford the A$1000 roughly to buy these latest components new when I was still happy with how the old PC was performing for at least another 12 months.

[Addiepower]

Thank you, I can't believe how quickly you reply here!  The REPLACEMENT MB is the Z97-AR.  So I am using all the components that I had in the original Z97 Pro Wifi AC.  From what I've read in the two manuals nothing should be an issue there.  I shall try your suggestions and get back to you.  I've unplugged anything that isn't needed to get to the POST screen. I'd be happy if I saw any life at all on the monitor at this stage.  By the way I konw the monitor works as I am writing this with my work laptop and use the monitor as an extended screen.  

Just for you info, the original Z97 Pro Wifi AC motherboard became faulty as the PSU would start up for 0.5s then shut off for 2 secs and repeat this cycle over.  The only way I stopped that was unplugging the 8 pin EATX from the MB and this let the PC start but it won't boot up without that 8 pin connected, hence getting a new, similar MB.

[Addiepower · Accepted solution]

Hi - Unfortunately I tried all that you suggested one by one and nothing would get it to boot into the POST stage.  The company from ebay in China that sold me the board also because involved and asked me to "Please prepare a dry toothbrush. Use a toothbrush to brush the CPU base pins and memory slots. This can solve most problems. Then use an eraser to wipe the back contacts of the CPU. Then try again".  This wasn't good advice as I got an old soft toothbrush and gently brushed the memory slots first, then went onto the base pins on the motherboard CPU are and this is what happened (see image).  The first pass i gently ran the toothbrush over the  pins it has created a slight bend in a few and this now will be useless.  You can see the pattern where they have been bent.  I can guarantee those weren't there before as I inspected the whole motherboard for any signs of over heating or damage to fine detail like that.  So you can shut the case as the MB has been ruined. 

Regards Adam.