Question Motherboard hangs with an i5 9400f

[Xenone]

I recently bought a used i5 9400f, the buyer was unable to confirm if the CPU worked or not, I decided to take the risk. I tried to post the CPU on my Asus tuf h310m-plus gaming motherboard since it's the only motherboard that I own that supports 9th gen (I never had a 9th CPU in it before so I have no idea if it posts with 9th gen CPUs but the BIOS is updated to latest which does support 9th gen, the CPU that I use in that m/b is Pentium Gold G5400 and it works fine.) When I have my Pentium G5400 in it, after turning it on, the motherboard will beep once very shortly and post, with the i5 9400f, after turning it on, the motherboard turns on as usual and all the fans spin but it doesn't beep, nothing happens, the motherboard stays on and fans keep spinning but nothing happens, no beep codes or reboots. When touching the bottom of the CPU cooler, I can feel the i5 getting warm.

Another interesting thing is, if I take out all of my RAM out and try to post with the G5400, it will give me 1 long beep and 2 short which means no memory/error with memory which makes sense, when I take out the RAM and turn on the motherboard with no RAM, just i5 9400f and GPU, the motherboard turns on and stay on with no error codes, not even regarding no memory. I tried cleaning bottom of the i5, I reseated it probably like 5 times now and I just can't get it to post, it just turn on and stays on and nothing else happens. Not sure if this could be the CPU fault since the buyer doesn't know if it works or it's a motherboard issue. I did contact the buyer and he is more than happy to take it back for full refund but I was wondering if theres anything else I can try. Thanks

 

[Justin Sisti]

You're in a tough spot it seems, if you cant confirm the mobo works then I think you should return the CPU. No point in driving yourself mad if you have 2 potential points of failure and no way to check.