RTX3070 Gaming pro power issue

[shaaamus]

Hi
have an issue with a Graphics card, am new to repairing graphics cards so will explain my findings as best I can

12v 3.3v 5v 1.8 & plex all present for about 15 seconds
then no plex, no voltage on the VRM no voltage to VRam 12v 3.3v & 5v remain present

I suspect faulty VRam as the resistance from what I believe to be the ram coils see picture with green box, is only 6.7ohms, shouldn't this be a higher resistance ?
2 of the VRam chips have black spots in the corners am not sure if this from the factory have enclosed a picture of this

any help would be appreciated
Thanks in advance

[foshland]

Re: RTX3070 Gaming pro power issue

Hi, the sticker near the pci is kind of dirty, maybe someone tried to fix it before? What about 1.8v after that 15 seconds? PEX voltage comes from 1.8 as I know

[shaaamus]

Re: RTX3070 Gaming pro power issue

Hi foshland
thanks for the reply, the 1.8v is there all the time, can be measured from the bios and coil by the PCI Slot, but pex is there on first power for around 15 seconds
voltages on the VRM again are there on power on but drop to zero, same with the Vram

[foshland]

Re: RTX3070 Gaming pro power issue

Ok, so look at the PEX circuit, its made assuming 1.8 is present, and if PEX is lost, Vcore is lost.

Find the PEX generation circuit and chip, after that, look if the enable for that circuit is lost after that 15 seconds, if enable goes 0V, try to find why, if it is there, it is faulty PEX generation circuit or chip.

This scheme is for Pascal GPUs, maybe it helps someway

https://repair.wiki/w/PEX_Rail_on_Pa...tic_pascal.jpg

[shaaamus]

Re: RTX3070 Gaming pro power issue

Hi foshland
I think you are right about the Pex Circuit, but I'm thinking this card has other issues, as the Vram resistance on this card is only 6.7 Ohms, have another rtx3070 here and the resistance on the Vram is 38 Ohms, & from what i can see it should be 30+ Ohms, will look at the pex system later though and let you know my findings

[foshland]

Re: RTX3070 Gaming pro power issue

Ah, ok, so the problem seems to be with the memory. Maybe any of them has a short of somekind and it makes the vram regulator to go to 0V and then disable other minor voltages.

Maybe you can inject 0.8V to 1V to rams and see if any of them heats up? (any mem or capacitor, resistor.. of that rail)

Do you have any schematics of any 3070?

[shaaamus]

Re: RTX3070 Gaming pro power issue

Hi foshland
Didn't even cross my mind to inject voltage on the VRAM circuit, thank you for that, that is why two heads are better than one as they say, will share my findings with you, may not get to it until Thursday/ Friday as work is manic at the moment

[shaaamus]

Re: RTX3070 Gaming pro power issue

Cannot find a schematic, so will just use diode mode to trace from the mosfet to the correct capacitor