Advice Pls help debug power to RTX A6000 in Dan A4-H20

[mikejmcfarlane]

Hi

I decided to update the RTX A4500 GPU in my Dan A4 H20 to an RTX A6000. But the GPU won't power up: the blower fan doesn't move when the PC starts which the A4500 does; there is no video output; the hardware isn't recognised in the OS (Ubuntu). The PC does power up and will boot with video out through the motherboard HDMI when the A6000 is connected.

The RTX A6000 has a different power requirement to the A4500, it uses 8 pin EPS/CPU ATX, rather than 6+2 PCIe for the A4500. It uses a supplied dual PCIe to EPS/CPU ATX adaptor. The dual PCIe plugs are powered with seperate cables from the PSU. Links to docs below.

I've tried:

1. Put the A4500 back in, working.
2. Tested all PCIe connectors are supplying power by plugging them individually into the A4500 and check it powers up, working.
3. Removed the PSU power supply to the A6000 and tried booting just with power from the PCIe slot, no effect.
4. Checked the BIOS PCIe setup for anything relevant, all I could see were bifurcation settings for AUTO or x16 to the PCI slot, tried both, no effect.
5. Given all power cables and connectors to the A6000 a good visual inspection and a good wiggle, no obvious issues or effect.

Any suggestions for further debugging I can try pls? Or do we think the GPU is DOA?

Over the weekend i will have access to a new tower PC with a full size Seasonic PX-1600 PSU, so could try the A6000 in that. Also do have access to another RTX A6000 I could try in the Dan, but it means opening the packing which would make returns more awkward, and if it's me having done something stupid and killed the first GPU I don't want to kill another. I do have a multimeter, but beyond using the continuity tester for fuses or that cables are connected, it's a mystery to me.


Docs I've read:

1. Quickstart, with details of EPS to PCIs adaptor https://images.nvidia.com/aem-dam/e...-pro-viz-ampere-qsg-108x63mm-20210803-r11.pdf
2. Workstation power guidelines, also with details of CPU 8-Pin Standard Adapter Cable https://www.nvidia.com/content/dam/...isualization/workstation-power-guidelines.pdf

Build is:
ASUS ROG z790-I gaming wifi motherboard
Corsair SF 750 PSU
Dan A4H20 with gen 4 PCIe riser
Not sure anything else relevant?

Thanks in advance for any help.

 

[mikejmcfarlane]

Also tried removing the riser cable and plugging the GPU directly into the motherboard, still not working. I would be really suprised if a card like this left the PNY factory not working, but i really can't now think of anything other than the GPU is faulty. So frustrating.

Any help or ideas would be appreciated, thnx.

 

[mikejmcfarlane]

I tracked down the problem, although it's strange.

Tried:

1. Swapping in a Seasonic PX-1600 PSU, still GPU not powering up.
2. Used the multimeter to try to check the pin out on the nvidia PCIe to EPS adapter, but couldn't make sense of the pin swaps as not a direct PCIe to EPS, looks like the two PCIe +12V must be spread across the EPS output pins rather than joined together.
3. Getting a bit frustrated, didn't help :-)

Stared at the test bench for a while and despite being a bit concerend the GPU was either faulty, or that I didn't have the skills to debug such an expensive bit of kit, that I was having fun. Engineers :-)

Decided to commit to the build and online return complexity ignored, and opened the second A6000. Starting with the PCIe to EPS connector, and the first A6000 powered straight up. So faulty adapter!

Using the multimeter, I then compared the pinouts of the working and the faulty adapters, and both exactly the same!

I'm really confused now. Does this mean some sort of mechanical fault that only occurs when the adapter is plugged in? Some internal circuitry or components (e.g. resistors) that are a bit different?

Any ideas?

 

[mikejmcfarlane]

I'm going to contact the online retailer and PNY on Monday to get a new adapter sent out, but wondering if I need it at all.

In theory according to the A6000 datasheet it should just be an 8 pin CPU connector. https://www.nvidia.com/content/dam/en-zz/Solutions/design-visualization/quadro-product-literature/proviz-print-nvidia-rtx-a6000-datasheet-us-nvidia-1454980-r9-web (1).pdf

As I understand it that is the same as an EPS connector, and the Corsair SF 750 has two such cable supplied. One goes to the motherboard, so can I use the other to the GPU?

Thing is, the connectors look a little different. Here is the supplied adapter connector:

Both the connector shapes (square/round), and the connector clip, are what is expected for an EPS connector according to https://www.overclock.net/threads/gpu-and-cpu-power-connections.1773088/


And here is the Corsair supplied EPS cable:

The connector shapes are a little different to CPU/EPS, but will mechanically fit into the A6000 connector. But the Corsair EPS connector is a split type so the connector clip is wider, and won't fit into the A6000 without being trimmed.

What to do? Can I check output voltage? Should be all 12V on the top row, bottom row is all ground? Anyone know all ok to just trim and fit? Check with PNY support, or just wait for new adapter?

 

[mikejmcfarlane]

Pinouts for the connector on page 10 https://images.nvidia.com/content/Solutions/data-center/vgpu-a16-product-brief.pdf

 

[mikejmcfarlane]

Time to get out the multimeter!

Watched a video on testing PSUs
Confirmed the pinouts for the PS_ON to ground wire https://www.playtool.com/pages/psuconnectors/connectors.html#atxmain24, and the pins to measure the voltage at https://www.playtool.com/pages/psuconnectors/connectors.html#eps8

And there is the answer. On the faulty adapter, the third 12V pin pin should be 12V, but is 0V :-)

The supplier responded quickly and a new adapter is in the mail.

But feeling confident i checked the voltages/polarity on the 4+4 pin CPU ATX cable were each 12V as expected ie same as EPS spec above. So modified the 4+4 connector double clip to fit, and the GPU powered staight up. No need for adapter and two PCIe cables, when can have a single CPU/EPS cable. I can't find the link now, but the GPU needs 300W peak, and a single CPU/EPS cable can supply this in combination with the power supplied through the PCIe slot.