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I'm from Germany and im not so good in English, please forgive me. I have a little bit idea of electronics but I'm not so sure with this problem. I would like to say beforehand that I have a soldering iron and hot air gun, so I can do a clean desoldering work. I have a dead 4901 MOSFET (link) on my vega56 and I would like to repair it. Now I have seen that the 780ti has a 4901NF MOSFET (link). My plan is to buy a dead 780ti and use it as a spare parts dispenser.
So the Question is: is the 4901NF okay to replace the 4901?
From what I understand from the datasheet of the 4901NF right now, it is the same as the 4901 apart from the fact that it can give more amps, but it nevertheless works, right? A new 4901 is expensive (20€, including shipping cost, from Mouser): does there exists an alternative seller for the 4901 or another graphics card mounting the same 4901 MOSFET? It's okay for me if the card is completely dead: I will learn to repair electronic stuff by myself and desoldering the card is a good exercise to do.

I hope that someone can help me

Daniele Tampieri
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ToastKiste12
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    Ignoring anything else, one of those two linked parts is 3mm x 3.5mm, whilst the other is 5mm x 6mm. So it is not going to work as a replacement. – Tom Carpenter Jan 09 '21 at 22:57
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    Googling "NTLLD4901NFTWG", there are a number of distributers that sell them. You'd be far better off buying one from a distributer rather than trying to salvage a part. Heck if the postage is too much, buy something else as well like a hobby electronics kit to play with – Tom Carpenter Jan 09 '21 at 23:03
  • Oh hell... thanks. im stupid... – ToastKiste12 Jan 09 '21 at 23:05

2 Answers2

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EU-Mouser does not stock these old parts 8 MOhm

USA-Mouser has stock <$2

https://www.digikey.ca/en/products/filter/transistors-fets-mosfets-arrays/289?s=N4IgTCBcDaIHIBUCyAxAIgFgJwAYCMIAugL5A

Try Digikey too.

Tony Stewart EE75
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More a long comment than an answer, but here it is.

So the Question is: is the 4901NF okay to replace the 4901?

Yes, but... The two devices seem to use the same chip mounted inside different cases so, apart from the different current rating, they can be safely interchangeable, however

  1. it would be difficult to match the thermal pads on the PCB, since the the replacement is smaller than the original one (as already Tom Carpenter noted in his comment), and
  2. if you nevertheless succeed in mounting the thermal pads in a clever way, you have to arrange pin connections as short and thick as possible, in order to minimize the additional leakage inductance they add and provide a sufficiently low resistance paths for the possibly large currents involved.

Finally I agree with Tom Carpenter's second comment and advice you to try to find a new part: apart from the difficulties described above, soldering/desoldering operations have a cost in term of reliability of the device. This implies that the newly mounted device could fail with a higher probability if it is an already used one.

Daniele Tampieri
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