Question When I mount to processor cooling fan, the processor no longer works

[garrettb2019]

I am building a PC and have run into a problem.
In essence: When I mount to processor cooling fan, the processor no longer works.

Details:
Motherboard: Asus Prime B450M-A
Processor: AMD Ryzen 3, which comes with its own cooler fan

I went ahead and built the PC, turned it on, and not much happened. Fans went on, but the processor did not POST. I undid the build and started troubleshooting bit by bit.

Symptoms
When processor and RAM is in the board, and I power the system up, the processor POSTs and I see on my monitor the start of the ASUS BIOS screen.
If I power off and then mount the cooler fan on the processor, and screw it to the board, the next time I power up, the processor does not POST – no beep codes, nothing.

I have tried this several times. I have tried removing the heat paste and re-applying fresh paste.

The motherboard comes with a back plate for use when mounting the cooler fan. These cooler fans have 4 spring loaded screws. It is quite some job to try and get them to catch.
I have tried, using a star method, to tighten each opposite screw a bit, and so son, until they were all tight.
I
So when I mount the cooling fan, the processor no longer POSTs. When I remove the fan, the processor does POST. (Although sometimes, the processor does not POST after the fan is removed, so I remove the processor, and then re-insert it, lock it back in, and it does work).

Questions
Has anyone come across this before? And if so, what was the cause?

My thoughts:
This has to be one of the following
Damaged processor (although I cannot see any damage)
Damaged motherboard (although I cannot see any damage)
Some error in the process of mounting the cooling fan

Any help / suggestions would be greatly appreciated

Garrett

 

[Dragos Manea]

Also too much presure on CPU can casue this, it may be also a short on the back when you mount the backplate. Look carefully when you mount the backplate to not short anything, also try to not tight the screw at maximum, because of the spring system you dont need too, just a little to be sure it is not wabbly.

 

[garrettb2019]

Thank you for the suggestion. I will try it out this evening and post the results

 

[Skazzi]

It's highly likely there's damaged electrical contact between the socket and the board.
Usually this often occurs with the socket if cooler doesn't have backplate.
If there's backplate and motherboard is new, most likely it's manufacturing defect, board should be replaced if seller provides warranty.

 

[garrettb2019]

This is frustrating. It is not a short at the back plate - the back plate has a non-conductive face on it.
Without mounting the fan, when I run the system, it POSTs.
When I powered up the CPU while pressing down on the CPU, it did not POST.
The nest time I pressed on all four corners, and it did POST.
I mounted the fan without screwing it in - it did POST
I secured the fan very slightly - it POSTed.
I tightened it a bit more. It didn't.
I loosened, tightened etc., and in the end... failed
I still don''t know what the real issue is...

 

[garrettb2019]

It's highly likely there's damaged electrical contact between the socket and the board.
Usually this often occurs with the socket if cooler doesn't have backplate.
If there's backplate and motherboard is new, most likely it's manufacturing defect, board should be replaced if seller provides warranty.

Thank you for this comment. I went ahead and returned it today. Sometimes, after exhausting all options that can be thought of, this is the best and only solution.
FURTHER UPDATE: Skazzi - your theory was correct. The failure was due to a damaged/faulty CPU socket. Replacing the motherboard solved the issue. I was able to return the original to the seller, and got a replacement. All's well that ends well.

 

[Skazzi]

Also i'd add to warn - when performing any mechanical operations with AM4 socket it's necessary to keep in mind that AM4 socket has very thin electrical contacts (1331 contacts overall, that is about 390 contacts more than on AM2/AM3 sockets) which often get damaged in case of removal processor cooler improperly.
Mechanical impact (directed to an opposite side from the board) to the socket's electrical contacts due to cooler removal, depending on the thermal grease condition might be enough to cause damage (tear off) to some contacts.
If thermal grease is viscid or dried up, probability to cause such damage to the socket is high.
Warranty for the motherboard is void if such damage takes place.

There are several ways of safe cooler removal, such as heating cooler up (that makes thermal grease less viscid), carefully twist or drag cooler to the sides (making thermal grease less adhere), unlocking the socket before cooler removal (not always possible), etc.. Though this subject is for another thread...

 

[garrettb2019]

Also i'd add to warn - when performing any mechanical operations with AM4 socket it's necessary to keep in mind that AM4 socket has very thin electrical contacts (1331 contacts overall, that is about 390 contacts more than on AM2/AM3 sockets) which often get damaged in case of removal processor cooler improperly.
Mechanical impact (directed to an opposite side from the board) to the socket's electrical contacts due to cooler removal, depending on the thermal grease condition might be enough to cause damage (tear off) to some contacts.
If thermal grease is viscid or dried up, probability to cause such damage to the socket is high.
Warranty for the motherboard is void if such damage takes place.

There are several ways of safe cooler removal, such as heating cooler up (that makes thermal grease less viscid), carefully twist or drag cooler to the sides (making thermal grease less adhere), unlocking the socket before cooler removal (not always possible), etc.. Though this subject is for another thread...

Thanks for the extra info. It will be helpful if any future surgery is required. I am stunned by the total number of pins!