Repair r9 390 nitro gpu

[JKKDev]

I removed the inductor from the memory vrm and the short between drain and source is gone but there is 0.2 ohm from ground to the other side of the inductor

I think at this point throw it in the bin or resolder everything on as nice as you can and sell it to the next fool (please don't do this ) You might as well desolder the RAM modules one by one until the short clears and then you can rest peacefully as there was nothing you could've done (if you don't have replacement RAM and reballing setup)

[Shock]

Anyway if you might as well check and rebuild the mem fets and and aux vrm so you can at least confirm you have good voltage and high resistance on the outputs up to the missing inductors.

If you still have a short on the memory side of the inductor the only thing you can do is remove caps then memory till the short goes away unless you have a thermal camera or want to power them externally like Wraper suggested. There is the high chance someone killed them rather than a graceful failure.

[more_stars]

Ohh, thank you guys for all the helpful thoughts.

I will wait for the other r9 card and see if the problem is the same. Maybe I will use this car for spare parts. I payd 20$ for this one and 25$ for the one that will come today.

[wraper]

Anyway if you might as well check and rebuild the mem fets and and aux vrm so you can at least confirm you have good voltage and high resistance on the outputs up to the missing inductors.

You cannot do that. Inductor is part of VRM with feedback voltage taken after inductor.

[Shock]

Anyway if you might as well check and rebuild the mem fets and and aux vrm so you can at least confirm you have good voltage and high resistance on the outputs up to the missing inductors.

You cannot do that. Inductor is part of VRM with feedback voltage taken after inductor.

Both the mem supply and the aux/memory controller supply? What is considered the output after the feedback then, the inductor side filtering caps or is it feedback all the way from the memory or gpu itself?

Do you have any documentation or schematics for modern cards? I know they put out boardviews for phones and macs is there anything for gpus?

[Shock]

Ohh, thank you guys for all the helpful thoughts.

I will wait for the other r9 card and see if the problem is the same. Maybe I will use this car for spare parts. I payd 20$ for this one and 25$ for the one that will come today.

Here is an example  (12m10s) of using a current limited power supply to limit the power into a short. He chose 1.2V as it was likely the lowest supply voltage on the board anyway. At 2A that is about a 0.25W into a short which was plenty to get that component warmed up.

[more_stars]

Perfect, then I will try that as soon as I get the other card as well. Now I will focus on seeing if I can repair the rx470 as I opened another ticket for that.

[Shock]

Cheers I'll check it out. You can say thanks to any post you find helpful by clicking on the "say thanks" button located on every post towards the top right.

[wraper]

Anyway if you might as well check and rebuild the mem fets and and aux vrm so you can at least confirm you have good voltage and high resistance on the outputs up to the missing inductors.

You cannot do that. Inductor is part of VRM with feedback voltage taken after inductor.

Both the mem supply and the aux/memory controller supply? What is considered the output after the feedback then, the inductor side filtering caps or is it feedback all the way from the memory or gpu itself?

Do you have any documentation or schematics for modern cards? I know they put out boardviews for phones and macs is there anything for gpus?

It's simply how buck converter works. It's not a linear regulator, it stores energy inside the inductor.

What is considered the output after the feedback then, the inductor side filtering caps or is it feedback all the way from the memory or gpu itself?

Wherever it's sensed, it's a single heavy power plane. Most likely connected somewhere nearby to first smoothing capacitors after inductor.

[Shock]

Yeah I know how the inductor and feedback works I was just having a blond moment while I was thinking about the best way of isolating the supply from the short and totally forgetting about the feedback on the output as well being shorted.

[more_stars]

Finally the second board arrived and after some checks, all the vrm seems to be fine but the board does not power and there is no video out.

The ohm readings from ground to coil below

Aux vrm 42 ohm
Ram vrm 118 ohm
Core vrm 21 ohm
0.98v rail 2 ohm

I think that the problem with this board is the ram chips as they are covered in liquid from the thermal pads. Is thare a way to fix those or do I need to replace them?

[wraper]

I think that the problem with this board is the ram chips as they are covered in liquid from the thermal pads.

It's a non issue. Like a half of graphics cards are like this.

[itsround]

Hey Alex,

i have a short in C4136 and C4135 so i need a new cap. Do you or anybody else know where i can buy caps like this?
I don't know the specs so i can't search. Can someone help me please?

Thank you in advance,
Patrick

[Mat2786]

Hello i have problème with my r9 390 sapphire nitro.
Can you help me?
Thank you
I have Black screen and no boot.
I have tested all Voltage and i have no Voltage to vmem.
And two capacitor.
Thank you

After other test i connect power supply  2 mosfet 4c10n have 12v
And 2 mosfet 4c10n 0v fuse 0v capacitor 0v see picture.
Thank you