Precision 5820 FlexBay questions (just ONE not working, why?)

Found a diagram and numbering of the flexbays. My PC is laying down, on its side...

Lower right is bay 1, drive/position 4 with nvme (that works).  Bay 1 drive/position 3 (upper right) is the one that doesn't work.  This text goes with the diagram:

"Two side-by-side pairs will be treated as a single FlexBay (Figure 1). The backplane consists of two pairs, so it must be replaced on a FlexBay basis."  So this must mean that the drive 3 in bay 1 is also setup for nvme only?  Even thought the connectors fit perfectly into an ssd or hdd??

When you set your PC laying down on its side, the upper and lower right are flexbay 0, the upper and lower left are flexbay 1.

The flexbay 0 shared the same backplane and if the lower bay worked with NVMe drive, the upper bay should too.  Note that your flexbay 0 don't work with SATA or SAS drives.

If you had performed the test properly, you can troubleshooting the issue by verifying that the cables connecting the backplane of flexbay 0 are securely connected to the motherboard miniSAS ports PCIe0 and PCIe1.  And verifying that both miniSAS ports are ENABLE in BIOS settings.

Otherwise, checking the physical port connector for any obstructions.

@Chino de Oro​ Thanks for the reply.  Your response seems to contradict the Dell documentation that I found, here

However, it does confirm why my other 'slot' is not working with a sata hdd.  Does anyone have a parts list or method to convert or modify the flexbay back to being sata or sas compatible?  I haven't found anything definitive.  

@Boznian2​ you cannot. the backplane for each bay is single and there's no half and half combination ( each backplane covers 2 drives and is either U.2/nvme or sata/sas ).

If you want to add another mechanical hdd, you need to use the 5.25" bay with an adapter 5.25" to 3.5" ( or 2.5" if going with that size )

Also, if you want to convert the flexbay from NVMe to SATA, you can replace the backplane with Dell part number TNNVP or M5CHV.  See example picture below.

@Chino de Oro​ You have helped me make sense of it.  I just could not figure out why only the lower right slot (#4 in my diagram above) was an nvme carrier, but the upper right slot (#3 in my diagram above) is a regular sata drive carrier (as are slots 1 and 2).  Maybe because it was a used machine?

Re:  I just could not figure out why only the lower right slot (#4 in my diagram above) was an nvme carrier, but the upper right slot (#3 in my diagram above) is a regular sata drive carrier (as are slots 1 and 2).  Maybe because it was a used machine?

I would not know the real reason, but I'm guessing the original owner had customized slot #3 with a SATA drive carrier for cost savings.  The NVMe flexbay carrier (part #66XHV) would cost about 5 or 6 times over the SATA drive bracket.  Many users just need one NVMe for boot drive.

I suggest that you keep the NVMe flexbay.  The flexbay SATA slots are hot-swappable, ready for storage expansion.  Therefore, you should not need to spend more money for SATA backplane conversion.  

Just thought to let you know that an NVMe SSD can be installed to slot #3 if your SATA carrier already has a 2.5" adapter bracket.  You can install NVMe SSD into a U.2 adapter, then install the U.2 adapter into SATA carrier.  See an example of U.2 adapter below.