Then you can keep using it but if the noise is too much, a better tech can fit a fan but the service cost means the better deal is a new power supply.
I don't see a make, model for this desktop PC but will give nods to best sellers on Amazon which thankfully are all single rail which is technical but keeps builders and repair folk out of trouble.
This is often a do it yourself repair with many youtubes and articles about this but check with forums to see if your new PSU looks to be the right one by supply PC details and a link to the PC maker's site for your model and a link for the new PSU.
Note: PSU is short for power supply unit.
I have this issue for about 2 monthes , every time im just opening the pc and cleaning him and it fix it for a few days but i understand that the problem isnt the dust because how much dust can ebter in a few days... i suppose that the fan of the power suplly makes the noise but i dont know why..and how can i fix that ?

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