AM5 build won’t POST. No-RAM shows DRAM Q-LED, but any DDR5 installed = PSU click and dead

padams81

Hey all - I’m stuck on a new AM5 build and I’m trying to figure out if this points to a bad motherboard vs PSU.

Parts: Ryzen 7 9800X3D,

ASUS TUF GAMING B650E-E WIFI,

Corsair RM1000x,

RTX 3080 (tested with and without),

Samsung 990 Pro 4TB,

32GB DDR5 (and I also tested a known-good DDR5 UDIMM from another PC).

Setup: board is on my desk (no case, and on the motherboard cardboard box), started by shorting PWR_SW pins. 24-pin ATX + CPU EPS 8-pin connected, CPU + cooler installed, one fan on CPU_FAN. Minimal config.

Behavior:

Standby power works (rear USB can charge phone)

With no RAM installed, board consistently shows yellow DRAM Q-LED (it knows that theres no memory in there)

With RAM installed (my kit or known-good DDR5), pressing power/shorting PWR_SW makes the PSU click but there are no LEDs, no fan twitch/spin, no Q-LEDs, nothing

Troubleshooting done: cleared CMOS multiple times, reseated CPU and inspected socket, tested single DIMM in A2/B2, tried known-good DDR5, updated BIOS via USB BIOS FlashBack (LED blinked then stopped)

Does this symptom pattern sound like a bad motherboard (memory power/init path), a PSU tripping, or something else I’m missing? Any last tests you’d recommend before I try to RMA the board or another component?