[SOLVED] Using a broken USB port led to no POST - PSU issue?

[neonplants]

Hey everyone,

My new-ish PC has been working perfectly for 6 months or so, but recently froze and now won't POST. The CPU diagnostic light on the motherboard is lit up, and I'm having trouble finding the source of the problem.

This all started when I pulled a USB 3 (type A) cable out of its connector on the front of my case, and the guts of the connector came out with the cable. I very stupidly plugged a different USB cable into the broken connector, which continued to work for a day or two. At some point, however, the PC froze, and has been unable to boot since. Everything lights up, fans spin, etc, but no POST. My guess is that using the broken USB port fried a different component.

I immediately disconnected the USB3 connector from the motherboard, and it still wouldn't boot. I re-seated the CPU with no luck, then replaced it with a different CPU. I got the same result both times, and no pins appear to be bent on either CPU. So I did a motherboard bench test, pulling all components except the CPU, and even with no RAM, the CPU diagnostic light stayed lit. Replaced the motherboard with a different board, put all components back in (except the broken USB3 connector), and the PC still won't POST. The CPU light is lit up on the alternate motherboard as well, with fans spinning and everything superficially working in the case.

EDIT: now the BOOT light is lit up, instead of the CPU light. I'm at a loss.

Here's my parts list:
PCPartPicker Part List: https://pcpartpicker.com/list/tttz9N

CPU: Intel Core i9-9900K 3.6 GHz 8-Core Processor
CPU Cooler: Scythe Mugen 5 Rev. B 51.17 CFM CPU Cooler
Motherboard: MSI MPG Z390 GAMING EDGE AC ATX LGA1151
Memory: G.Skill Ripjaws V Series 32 GB (4 x 16 GB) DDR4-3200 CL16 Memory
Storage: PNY CS900 500 GB 2.5" Solid State Drive
Storage: Samsung 970 EVO Plus 2 TB M.2-2280 NVME Solid State Drive
Storage: Seagate Barracuda Compute 2 TB 3.5" 7200RPM Internal Hard Drive
Storage: Seagate BarraCuda Pro 10 TB 3.5" 7200RPM Internal Hard Drive
Video Card: Gigabyte GeForce GTX 1650 SUPER 4 GB WINDFORCE OC Video Card
Case: NZXT H510i ATX Mid Tower Case
Power Supply: Thermaltake Smart 600 W 80+ Certified ATX Power Supply
Capture Cards: Elgato Game Capture HD60 Pro, stream and record in 1080p60, superior low latency technology, H.264 hardware encoding, PCIe (x2)


Thanks so much for your help.

 

[mdd1963]

Could be a PSU and/or a mainboard...

Most would try a PSU first. (When you try a PSU, ensure you do not mix any modular cables from old PSU with new one, or, vice versa, as pinouts at PSU insertion points differ greatly)