Dell R720 12 bay backplane power harness question

[Razor Blade]

I was hoping someone might know the answer to this. I'm trying to pin-out the wire harness from a Dell R720 and it appears the color scheme is a bit different. Does anyone know if the yellow still means +12V and black is ground? Also I am trying to figure out if gray is +5V or something else.

 

If anyone can provide some information I would greatly appreciate it. I've also attached a high res photo of the cable for reference.

 

Thanks in advance!

Spoiler

[cj09beira]

if that is a pcie 8 pin then its 4 ground wires 3 12v power lines and a sense line (the gray one)(btw sense line is also a ground wire)

[dalekphalm]

39 minutes ago, Razor Blade said:

I was hoping someone might know the answer to this. I'm trying to pin-out the wire harness from a Dell R720 and it appears the color scheme is a bit different. Does anyone know if the yellow still means +12V and black is ground? Also I am trying to figure out if gray is +5V or something else.

 

If anyone can provide some information I would greatly appreciate it. I've also attached a high res photo of the cable for reference.

 

Thanks in advance!

  Reveal hidden contents

I'd suggest just going out and buying a Multimeter (if you don't own one - they're an essential tool everyone should own anyway), and measuring the pins.

[Razor Blade]

@cj09beira Thanks for the reply!

 

The connector I believe it looks something like a molex nano-fit connector. I'm not able to positively identify the exact connector though. The harness provides power to a 3.5" hard drive backplane so I know it would need to at least supply 12V. I'm not sure if the backplane also supports 2.5" drives because if it does it would either need a VRM on the backplane to supply 5V or that gray wire might be 5V...that's kinda where I'm stuck. 

 

@dalekphalm

I don't actually have the rest of the system to measure it. I got the backplane on ebay for next to nothing and am wanting to see what i can do with it.

 

Seems like documentation online is a bit scarce for this product...

[dalekphalm]

4 minutes ago, Razor Blade said:

@cj09beira Thanks for the reply!

 

The connector I believe it looks something like a molex nano-fit connector. I'm not able to positively identify the exact connector though. The harness provides power to a 3.5" hard drive backplane so I know it would need to at least supply 12V. I'm not sure if the backplane also supports 2.5" drives because if it does it would either need a VRM on the backplane to supply 5V or that gray wire might be 5V...that's kinda where I'm stuck. 

 

@dalekphalm

I don't actually have the rest of the system to measure it. I got the backplane on ebay for next to nothing and am wanting to see what i can do with it.

 

Seems like documentation online is a bit scarce for this product...

Can you post the PN for that backplane? It's not quite visible in the picture.

 

The User Manual for the R720 clearly lists where the backplane connector plugs in. Socket: J_BP3. But I cannot find a pinout diagram for it.

 

What exactly would you like to do with this backplane?

[Razor Blade]

1 minute ago, dalekphalm said:

Can you post the PN for that backplane? It's not quite visible in the picture.

 

The User Manual for the R720 clearly lists where the backplane connector plugs in. Socket: J_BP3. But I cannot find a pinout diagram for it.

 

What exactly would you like to do with this backplane?

Sure!

 

The part number for the backplane is PGXHP

The part number of the cable is 123W8

 

The story goes like this. I bought an empty R720 12 bay chassis because the drive trays and spare fans it came with (what I was after) were cheaper than buying all that stuff separately. Turns out it came with the backplane also. Which is a pretty sweet bonus! I was going to see if the backplane would pass through drives to a raid card. If it works I was going to keep the chassis and could maybe make it into some sort of DAS box project. The more I look into it the less likely it seems but like I said there is little to no documentation online I can find for the actual electrics on this.

[Razor Blade]

After looking around I've run across this person trying to add a power connector for a graphics card on a Dell R820

 

https://hackaday.io/project/39167-pcie-x16-auxiliary-power-for-dell-poweredge-r820/details

 

it appears maybe it is a +3.3V sense wire? Not sure how the backplane handles it...maybe the signal is to turn on the drives? I'll have to mess around with it more...just don't want to blow it up is all.

 

Thanks for the help!

[dalekphalm]

1 hour ago, Razor Blade said:

Sure!

 

The part number for the backplane is PGXHP

The part number of the cable is 123W8

 

The story goes like this. I bought an empty R720 12 bay chassis because the drive trays and spare fans it came with (what I was after) were cheaper than buying all that stuff separately. Turns out it came with the backplane also. Which is a pretty sweet bonus! I was going to see if the backplane would pass through drives to a raid card. If it works I was going to keep the chassis and could maybe make it into some sort of DAS box project. The more I look into it the less likely it seems but like I said there is little to no documentation online I can find for the actual electrics on this.

I see. The backplane will definitely connect to a RAID card or HBA. It should have multiple SAS connectors on it (how many depend on how many bays - with a 12-bay chassis, it’ll be either 2 or 4 SAS connectors, likely). 

 

Ideally you would pick up the R720 motherboard and just use that. Otherwise it’s going to be difficult to rewire the backplane to work with a standard PSU. 

[Razor Blade]

1 hour ago, dalekphalm said:

I see. The backplane will definitely connect to a RAID card or HBA. It should have multiple SAS connectors on it (how many depend on how many bays - with a 12-bay chassis, it’ll be either 2 or 4 SAS connectors, likely). 

 

Ideally you would pick up the R720 motherboard and just use that. Otherwise it’s going to be difficult to rewire the backplane to work with a standard PSU. 

The plot thickens... So it appears that the R720XD backplane has a SAS expander built in which is why it has the controller on the actual backplane. (the IBM X3650 7979 had a similar feature where the back plane had 6 drives but only one SAS cable out of the backplane). There are 3 SAS ports (A,A1 and B) However A1 is for the flex bay (a small 2 bay backplane on the rear of the server).

 

Most of the other connections are for the front I/O. So it seems the only unknown thing at this point then is that 3.3V gray wire and if the back plane needs some sort of I2C signal to work. From what I've read it appears the I2C cable appears to connect to the raid controller for diagnostics and communications like that.

 

I'm not concerned about making a power adapter. I have hot air rework station and am pretty experienced with soldering if I was to replace the power connector, or a molex crimping tool if I decide just to make a cable adapter. If this backplane works I already have a 2U lite-on PSU out of a Dell R5500 I could use. I think I may pursue this, if I can make a kind of low power DAS out of this chassis, that would be interesting. If not and I blow up the back plane, I still have my drive trays and fans.

[dalekphalm]

27 minutes ago, Razor Blade said:

The plot thickens... So it appears that the R720XD backplane has a SAS expander built in which is why it has the controller on the actual backplane. (the IBM X3650 7979 had a similar feature where the back plane had 6 drives but only one SAS cable out of the backplane). There are 3 SAS ports (A,A1 and B) However A1 is for the flex bay (a small 2 bay backplane on the rear of the server).

 

Most of the other connections are for the front I/O. So it seems the only unknown thing at this point then is that 3.3V gray wire and if the back plane needs some sort of I2C signal to work. From what I've read it appears the I2C cable appears to connect to the raid controller for diagnostics and communications like that.

 

I'm not concerned about making a power adapter. I have hot air rework station and am pretty experienced with soldering if I was to replace the power connector, or a molex crimping tool if I decide just to make a cable adapter. If this backplane works I already have a 2U lite-on PSU out of a Dell R5500 I could use. I think I may pursue this, if I can make a kind of low power DAS out of this chassis, that would be interesting. If not and I blow up the back plane, I still have my drive trays and fans.

Just to clarify: a SAS expander and a SAS RAID Card/Controller are different things.

 

A SAS expander simply takes a single 4-channel SAS cable, and multiplies that to as many channels as the Expander supports (Usually there's a hard limit, and there's also a practical bandwidth limit too).

 

So that SAS port on the expander still needs to be plugged into either a SAS Raid Controller, or a SAS HBA. Many Server motherboards have these integrated onto the motherboard, or it might be an add-on card. But in either case, the RAID Controller or HBA would not be inside the Backplane.

[Razor Blade]

1 minute ago, dalekphalm said:

Just to clarify: a SAS expander and a SAS RAID Card/Controller are different things.

 

A SAS expander simply takes a single 4-channel SAS cable, and multiplies that to as many channels as the Expander supports (Usually there's a hard limit, and there's also a practical bandwidth limit too).

 

So that SAS port on the expander still needs to be plugged into either a SAS Raid Controller, or a SAS HBA. Many Server motherboards have these integrated onto the motherboard, or it might be an add-on card. But in either case, the RAID Controller or HBA would not be inside the Backplane.

Yes I believe the back plane has a SAS expander built in which would explain why there are 2 SAS ports for 12 drives. The third port A1 connects to a flex bay back plane. I was planning to run those to a RAID card and provide power to see if any drives show up. Though this could all be a fruitless effort if that back plane doesn't want to play ball or it does not completely pass through drives to the HBA.

[iJarda]

I have Dell R7910 (equivalent to R730) so I can measure that one for it's 2,5" inch backplane if that would help, but I think whole backplane should just need power

 

sense pin is used also on 8-Pin for PCIe cards where it has 3.3V on that pin connected to pin where other PSUs or 8-pin graphics cards has ground which is internally connected ... so it just "shorts" 3.3V sense to ground and system then knows that this piece of HW is present or not

(for example my R7910 knew about my backplane which throwed error when I haven't connected SAS cables and even if I have unplugged backplane control cable, it still throws error that theese cables are missing - it was based on that power cable with sense pin => so sense pin matter for system board, not whole backplane)

[Razor Blade]

At this point I'm not sure if it will work independent of the motherboard. I hooked up the 12V to yellow, Black to ground. I tried a 6 pin and 8 pin PCIe supply for power. Measured 12V so I know it is getting power. I tried a single drive in 3 spots but the drive did not power on. Could be the back plane is dead, or maybe there is some sort of element I'm missing. I though it had to do with the gray wire but at this point I'm not sure i want to keep messing with it.

[iJarda]

11 hours ago, Razor Blade said:

At this point I'm not sure if it will work independent of the motherboard. I hooked up the 12V to yellow, Black to ground. I tried a 6 pin and 8 pin PCIe supply for power. Measured 12V so I know it is getting power. I tried a single drive in 3 spots but the drive did not power on. Could be the back plane is dead, or maybe there is some sort of element I'm missing. I though it had to do with the gray wire but at this point I'm not sure i want to keep messing with it.

These backplanes, especially SAS drives do that, as they don't power up till controller don't call them to spin up, on some systems it spin up drives one by one to not create current peaks.

[jamison]

Interesting. I am trying to do the exact same thing (use backplanes pulled from old R720's in a custom-built JBOD chassis). I've been tracing the pins on the 8 pin molex nano-fit connectors with a multimeter. I wish I had access to a working R720 motherboard to experiment with...

[Razor Blade]

I did mess around with this one more time as I wanted to make a last ditch effort to get it working... but alas I believe the motherboard communicates with the SAS expander built into the backplane. Without the proper signal the backplane never "wakes up". If there was a way to tell what signal it is looking for I would imagine one could replicate it with an arduino or something. Eventually I'm going to just build a SATA hot swap backplane for it. Mainly I'm going to do it for the looks...it would be way easier to pick up a norco case and be done with it.

[jamison]

I am reluctantly coming to the same conclusion. I tried a backplane variant that doesn't have an onboard expander (part no RVVMP), but similarly no luck. Upon closer inspection, even the expander-less backplane has an AVR microcontroller, which means that it could potentially be performing very advanced logic onboard (iJarda's comment about staggered drive poweron makes a lot of sense)

 

I did find out that running 12v through the AVR's 5v input gets all the LEDs on the backplane to light up (at the expense of sending the AVR up in smoke )

[snailium]

I'm landing onto this page when I'm googling Dell server power connector pinout.

 

I have similar situation. I'm connecting to a PCIe expander instead of SAS backplane using Dell kit P/N 86M4K. This kit has a PCIe SAS expander card and a riser card. And the power is required for the riser card.

 

On the riser card, there are LEDs for power checks on 12v, 3.3v and 3.3v standby. I followed the pinout from Kevin's hackaday.io project. I can get the 12V power light up, but not the 3.3v and standby. I think the 3.3v is the key to get everything working.

 

@Razor Blade@jamison, have you got your backplane working? I'm trying to figure out how to get the 3.3v working.

 

Thanks.

 

EDIT: I've modified the mini 8-pin power cable using a 5-wire SATA cable. I know my PSU gives 3.3v to the SATA cable, checked by using a voltage meter.

 

Something I've tried for wiring.

- connect both grey wire to 3.3v

- connect the grey wire on the ground side to 3.3v, leave the other unconnected

- connect the grey wire on 12v power side to 3.3v, leave the other unconnected

I can confirm 3.3v is populated correct on each of the setup. None of them can lit up the 3.3v/standby check lights.

 

I'm stuck here.

 

EDIT2:

I tried to use my multimeter to investigate the "3.3v sensing" wire while system is running and everything connected. Basically, the riser card or the backplane should short the "sensing" wire with the 3.3v input, and feedback 3.3v to motherboard to show a presence. So it is not a good idea to short the "sensing" wire to ground.

 

Now I'm thinking maybe there is some mechanism inside the 16-pin signal cable (P/N KV109) to enable the board. Something I can think of

- there is a detect signal, which connects to either 5V/12V or ground

- it provides serial connection (UART or RS232), and the connection needs to be established