PSU failed after two days, can MOBO be cause, how to check MOBO for shorts?

I need some advice...

I purchased a Gigabyte Gaming X Z390 MOBO, an Intel I7-9700K CPU, an Intel SSD 665 1TB, and 32 MB of Corsair memory from Micro Center. I also got an EVGA 110-BQ-0600-K1 PSU, a Scythe Mugen 5 Rev.B cooler, and a Corsair 100R case from Amazon for the build. I reused a Seagate Barracuda 1TB HDD, a Gigabyte Radeon HD 7800 video card, and an optical drive from my old computer. I did not put the video card in the first day.

The build went well with YT help from Carey Holzman, and the machine ran perfectly for two days. I was using Open Hardware Monitor to check temps and another (cpuid) monitor for SSD temps. Assorted processing was excellent

Then the PSU failed and the machine would not respond to the power switch even though LED's were lighting up.

I disconnected the PSU and used a multimeter to ascertain that some 3.3 V pins were live but all 12 V pins were dead (using MOBO manual to id pins). Amazon is shipping me a replacement PSU.

The problem may have been a surge (my SP was very old) due to a charging item on the SP and possibly a vacuum cleaner trying to eat a rug corner. -- OR -- it may have been a short somewhere on the MOBO. I might have heard some faint clicking but am not completely sure.

Now, before I put in a new PSU, is there a way to verify the MOBO is not shorting? Can Micro Center test bench it for me?

Thanks -- JD