Help with Rx 480

[Scotchmist]

I have two identical Asus rx480 GPU, both do not power up and display.

1st card I checked all around for a short, just after the chokes all caps are showing short to ground

2nd card I had in the motherboard to test and was showing the same symptoms so immediately removed and checked the same area for shorts and all caps short to ground. This time however three MOSFET were showing a short.

I got my rework station out to swap out the faulty MOSFET. While it was warming up I was going to mark up the faulty ones and the short was gone

I put both cards in the motherboard and the short appears on both the cards MOSFET and then goes after a while.

Any ideas on what is causing this, the shorted caps are there all the time should I just remove and check them all?

Thanks

[Scotchmist]

Re: Help with Rx 480

Attached photo

[Scotchmist]

Re: Help with Rx 480

I have done some more testing on these, found some caps near the 12v power and Digi vrm ic

I removed both caps and both found to be ok and short is still present on pads, so removed the Digi vrm ic all shorts still present.

So all shorts are in the same area and only thing I can think of is to remove all caps after the choke but there are 37 of the buggers

Tried hooking up a regulated PSU to try find the short but it has short protection and will not put any amps into the card.

Any ideas before I remove the caps would be appreciated

Thanks

[TheQuentincc]

Re: Help with Rx 480

Why do you believe this capacitor bank is shorted ? Do you know that you are measuring GPU core resistance which is very low.
Try removing coil at first, then you can know if it's the core/memory which is shorted or if it's the "power supply" area that is shorted.
Also if you are replacing mosfet and they shorted themselve quickly, that mean you have something "after" which is shorted.. or sometime it's caused because mosfet don't get 12V power supply or there is something wrong with the load balancing.

[Scotchmist]

Re: Help with Rx 480

Hi,

All the electrolytic and ceramic caps after the coils are short to ground.

On one card I found a short cap near the Digi vrm ic but removing both did not clear the short

On the other card the cap near the Digi vrm is not short to ground however I found a cap on the side near the display output short, I removed this but the short remains (this is not a short on the other card)

I will do a bit more testing