A soft drink spilled on my unplugged PC. I cleaned it with distilled water and 99% isopropyl alcohol and let it dry for several days, but it still won't pass POST.
The build has a B650M Pro RS WiFi motherboard, a Ryzen 5 7600X and Crucial DDR5 memory. The memory and graphics card weren't installed during the spill. Can I use another motherboard to test the CPU and RAM, or does it need to be the same model?
You don't need the same model. An AM5 motherboard with DDR5 support can be used to test that CPU and memory. Check the board's CPU support list and BIOS requirements before buying, though, since compatibility can depend on the installed BIOS version.
A replacement board is still a purchase just for a test. If it works with your parts, that points toward the original motherboard or another part of the original setup, but it doesn't by itself explain the damage.
Before buying anything, check the motherboard's diagnostic LEDs. They are labelled CPU, DRAM, VGA and BOOT, near the memory slots. Note which one stays lit when the startup attempt stops.
That gives you a starting point, not a guaranteed diagnosis. For example, a DRAM light means memory initialization is where it got stuck, but it doesn't prove the stick itself is bad.
Try a bare-bones setup outside the case to rule out a case short. Disconnect power first, then put the motherboard on plain cardboard and connect the CPU and cooler, one RAM stick, the power supply and a display. The 7600X has integrated graphics, so you can use the motherboard's video output without the graphics card.
Leave storage and other peripherals disconnected for the initial test. Make sure the board is completely dry and inspect it for any remaining sticky residue before applying power. Liquid can get under components or into connectors, where a surface cleaning might not reach.
The RAM and graphics card being out during the spill is encouraging, but it doesn't establish whether the CPU or motherboard survived. If a minimal setup still fails, a repair shop is another option to weigh against the cost of buying a test board.
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42v~grommet_815:
Do repair shops use boards with better diagnostics, or are the LEDs about all there is?
x7!lunchpail_406:
Some boards have numeric POST code displays, and repair shops may also use dedicated diagnostic tools. The LEDs are less detailed, but they're a useful place to start.