Z390 stuck pre-POST on code "7F"

Hello,

I recently changed my CPU cooler from an old Hyper 212 to a nicer, much better, Noctua DH-15S. I have the ASRock Z390 Taichi with an Intel 9900K and Asus Geforce GTX 1660 Super in there, BIOS version 1.8 and was having ZERO issues with the machine before replacing the cooling tower.

After replacing the cooling tower, I wanted to add another SATA device and plugged one in at which point the Dr. Debug LED showed me a SATA error, so I powered the machine off and disconnected the SATA drive, leaving only my main SSD plugged in. The next time I tried to boot, and every single time after, the Dr. Debug LED shows the code "7F" for about 30 seconds, and then the machine attempts to restart only to show the same message...again.

I've reseated EVERYTHING more than once, tried with just the CPU and one stick of RAM and nothing else (aside from the cooler)....no luck. I left the motherboard disconnected from power for many hours just to make sure there was absolutely no chance of any remaining electricity...still nothing.

Can anyone help? I have tried everything I can think of, but I don't think I'm actually managing to clear CMOS (have disconnected it from power, used the power button to draw any remaining, cleared all cables and removed the battery, used both the CLEAR CMOS "smart button" as well as a jumper on the two pins (the motherboard doesn't come with a jumper, but I have an old one that should still work fine), even going to the point of shorting the positive and negative BIOS battery circuits. Still, I have the blue glow of RGB preferences I set in the BIOS (its the only visual cue I get, since I get no display output). Can anyone tell me maybe what the default RGB color is so that I might recognize it? Shouldn't/wouldn't a CMOS reset change it back to default?

I've contacted ASRock technical support about this, but since its been 3 days since I first contacted them I thought I'd go ahead and see if any of you fine folks have heard of/seen this issue.

If I could even get a solid reason for the "7F" I would be happy - the machine is new enough that if necessary ANY of my components could be RMA'd (though, since like I said, they were working until I made my "upgrade" to the cooling, so I'm not sure its an issue best solved by a RMA). But it's not well-documented in the manual, and I can find NOTHING about it (except as it relates to EVGA and AMIBIOS products, not ASRock). Anyone who can help point me in the right direction is doing me a huge favor.

Thanks in advance for reading this (and hopefully replying :D)!

Yup, tried all of that and were a bit more. The RAM and CPU are confirmed working (they work perfectly sitting in a Gigabyte AORUS Pro as I right this).

It doesn't much matter, since customer service already issued me an RMA and the motherboard is on its way back to the RMA department also as I write this.

Thanks for trying, though.

You can try opening a support ticket with ASRock directly:
https://tw.asrock.com/events/tsd.asp