Question GPU mosfet replacement

[Carlsos]

I have an Asus RX580 Dual (8GB) that has a shorted mosfet that I need to replace, I already removed it and it works without it. I have seen that they say that you have to replace all the mosfets of the same phase even if the others are fine, my question is why is it necessary? This one has 3 mosfets per phase and the mosfet in cutoff had been changed previously.

 

[Darkbreeze]

The answer, literally, is the first google result.

When multiple MOSFETs are used in the same phase of a circuit (typically paralleled to handle higher current), they should ideally be replaced together because even slight variations in their internal resistance ("on-resistance", RDS(on)) can lead to uneven current sharing, causing one MOSFET to carry significantly more current than the others, potentially overheating it and causing premature failure; replacing all MOSFETs in the phase ensures consistent performance and prevents this imbalance.

And now you probably understand why that mosfet failed early and the next one likely would too.

 

[Carlsos]

I have searched on Google and I can't find anything, I don't know what terms to use for the search.

In this case the defective mosfet is a mosfet that is in series with the other two, and is of a different value than the other two, although they are still in the same phase.

If the problem is the internal resistance, then do they have to be mosfet from the same batch? What about the mosfets sold on eBay? I can't even guarantee that they are new.

 

[Darkbreeze]

No idea. The vast majority of us don't repair motherboards or graphics cards. These are basically replacement items in most cases, for most people, when they fail. I've done some mosfet and capacitor replacements on some power boards for TVs but that's a lot less complex.

 

[beyondlogic]

I have searched on Google and I can't find anything, I don't know what terms to use for the search.

In this case the defective mosfet is a mosfet that is in series with the other two, and is of a different value than the other two, although they are still in the same phase.

If the problem is the internal resistance, then do they have to be mosfet from the same batch? What about the mosfets sold on eBay? I can't even guarantee that they are new.

a large majority of of repairs of this type of work are done with donor parts. so if all of them have to be replaced it will most likely come from a card that has all of those intact. otherwise the manufacturer would be the next port of call.