HELP! Supermicro 846 Chassis, New Build, Won't Boot

hansolo77

New Member
Jul 16, 2020
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I'm trying to build a new server using an MSI X570 Unify and a Ryzen 3900X CPU. All specs should work. But when I connect up the power and try to turn the system on, nothing happens. The backplane makes one quick beep and shows a short little blue LED that slowly fades away. I'm not sure what's going on. At first I tried to use Google and found this forum with other people looking for help. One suggestion for the beep was that the backplane may have been looking to detect fans attached to it. So I tried connecting them to that, made no change. I then tried putting a jumper of the fan detect pins. Still nothing. I'm at the point now where I've got the motherboard disconnected from the power and I'm just testing the power supply by tripping the Power_ON (green wire) with a ground (black wire). Still, the backplane just gives me a quick beep and then dies.

Is my backplane dead? Is it the power supply? Is it the power distribution unit? I'm completely lost. From the looks of it, the power supply won't send full power down to the motherboard unless the backplane is happy. Any ideas? Something I'm missing?

Backplane is a BPN-SAS2-846EL1

Thanks for any help!

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UPDATE
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I disconnected power from the backplane completely. I then disconnected both the 24-pin and 2x8-pin power connectors from the motherboard. Now nothing is connected. Tested the power supplies again by tripping the 24-pin wires. Still get that beep sound, and it's coming from the power distribution unit. Faulty PDU? It's # PDB-PT846-8824.
 
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psc

Member
Jun 30, 2019
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I get a beep when I turn my chassis on, and they're working fine; I've no idea which component it comes from, but it's probably the same beep. I'd start simple; will the motherboard power up without anything else connected? If so, then what about the mid-chassis fans when the backplane is connected to power? If not, then when you manually trigger the power, do you see voltage on the other pins (either ATX or the other connectors)? The PDU shouldn't care about the backplane, AFAIK: they both support I2C but I don't think they're connected (at least by default).
 

hansolo77

New Member
Jul 16, 2020
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I think the beep you get might be the motherboard POST confirmation. My other computer does that when I power on from a cold boot. As for the motherboard powering on, it doesn't. When I connect the power cables to it, then plug in the PSU to the wall, the motherboard's power button turns on, and the PSU light is yellow. Then when I push the power button, I get that beep and then everything shuts down. Like it wants to work, but the thing just dies instantly. When I had the fans connected to the backplane, they tried to spin but never even made a single revolution. With everything disconnected, I plug the PSU into the wall, the PSU light is yellow, then I force trip the leads on the 24-pin connector, and I get that beep then nothing else. The fans on the PSU don't spin up. Also, the PSU light stays yellow, it doesn't turn red to indicate a fault or anything.

I will try to do more testing today. I think it's a bad distributor.
 

hansolo77

New Member
Jul 16, 2020
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I definitely think it's a bad power distributor. I just tested the 24-pin connector with a multimeter. When I test the +12v leads I'm getting some crazy numbers like 67-68v. When I test the +3v leads I'm getting only about 1v. The +5v leads don't even register. Granted, I could be doing it completely wrong, but I watched some youtube videos where they're testing on GOOD power supplies and I'm not getting anything like what I should be expecting.
 

hansolo77

New Member
Jul 16, 2020
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Ok, it's definitely the power distributor. I pulled out my main computer and connected the power supply from that to the server motherboard. I couldn't get the 8-pin connector out without gutting the whole computer, so I just used the 24-pin. All I did was connect it and power it on. The fans all came on (even the one on the cpu and the pci slots). I don't have a video connected right now so I couldn't see anything, but the motherboard powered on. I then disconnected it and removed the power distributor to see if there was any visible damage (blown caps or something). The top/front of the distributor looked fine, but once I removed the mounting plate .... it's ... yeah dead. I took a picture of it (see the link). I bought the chassis from TheServerStore via a direct chat line with one of their reps. I emailed him before I tested with the other power supply asking if there was any way I could RMA it since it looked like it was the problem. After I saw the burnout and had the picture, I went back and was going to update my threads showing the damage. The sales rep had already gotten back to me and said it would be no problem to replace. Apparently they have a few damaged cases that they pick replacement parts from. He's out of the office until Tuesday but said he'd send a request over to them so a replacement could be sent out real quick. That's awesome. I really like this company. They're willing to bend the rules and sell me a case that they didn't have available, then go further and support a damaged distributor before I even had visual proof it was bad. When I bought my Norco RPC-4224 case, their staff was so short and rude with me and was unwilling to RMA my 2 damaged backplanes, making me rebuy them. They also charged me for drive caddy screws because they forgot to include them. Yeah, I'm definitely sticking with these guys. :)
 

Fallen Kell

Member
Mar 10, 2020
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Well, that is definitely one of the differences between a Supermicro case and a Norco. With the Supermicro, there are lots of parts around because they were designed from the get go to have everything replaceable in case of failure (because it is enterprise grade), and lots of the cases were made along with replacement parts for maintaining. I love my 846, best decision I made for my storage server.
 
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msg7086

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May 2, 2017
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before I even had visual proof it was bad
Well, people who bought those equipment usually don't lie, especially on these parts. A PDU is not worth any money anyway. Also I agree with Fallen Kell. SMs are made in enterprise grade and have plenty of used parts on the market. It's just so easy to work on those / replace or swap parts as you like. I just got a 825TQ which is also extremely easy to work with. The SMs are just fantastic.
 
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pablocool

Member
Mar 13, 2012
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Poland
Hi I have PDU PDB-PT846-8824 and PSU PWS-920P-SQ. Both components are fine and boot correctly two of my supermicro baords. However when I try to boot Asus P8b and another 1151 socket gigabyte board with them I just fail. Both boards are fine. Boot correctly with Corsair psu. So why supermicro psu and PDU wont boot not server grade motherboards Asus/gigabyte?
 

itronin

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Nov 24, 2018
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Denver, Colorado
Hi I have PDU PDB-PT846-8824 and PSU PWS-920P-SQ. Both components are fine and boot correctly two of my supermicro baords. However when I try to boot Asus P8b and another 1151 socket gigabyte board with them I just fail. Both boards are fine. Boot correctly with Corsair psu. So why supermicro psu and PDU wont boot not server grade motherboards Asus/gigabyte?
did you make sure to change the position and remove all unused standoffs from the motherboard area when switching between the supermicro and the ASUS/Gigabyte boards?
 

pablocool

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Mar 13, 2012
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Poland
I have all components out of the chassis. I just swap corsair psu with supermicro psu and pdu. In motherboard there is only ram and cpu. Of course I pay attantion not to make any short. I even check all voltages in ATX connector from pdu and EPS connector. All are fine (they had to be as supermicro motherboards boot correctly). I cannot figure out what is the incompatibility Point. I also asked supermicro support about this use case. They claim third party motherboards should be supported. Does anyone successfully used third party motherboards (Asus/gigabyte/msi etc) with supermicro psu/pdu?
 

itronin

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Nov 24, 2018
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Edit - I see what you meant by PDU

PDU/PDB I'm using the stock models installed in the chassis I listed.


Is it possible the SM boards generate a power load at a certain level and the Asus and the Gigbayte are below that and the PDB is looking for that minimum threshold? I've seen this issue before though not in a long time and it was on consumer PSU's.

To test it, just hook up a couple of spinners that will spin up immediately (not delayed start or wait for spin up command) along with the asus & gigabyte boards and see if things come to life.
 
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pablocool

Member
Mar 13, 2012
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By PDU I meant Power Distributor Unit. This is also called PDB Power Distributor Board. That sounds very interesting what you have written. I will check it. I read about ATX Pinout. There is one interesting pin:

PWR_OK or “Power Good” is an output from the power supply that indicates that its output has stabilized and is ready for use. It remains low for a brief time (100–500 ms) after the PS_ON# signal is pulled low.

I guess this is information from PSU to the motherboard that "everyting is fine" and then motherboard know it can continue to POST. My definitely refuses. So maybe it does not receive answer from PSU on that pin.

To add more confusion I tested old Pentium 4 motherboard with some P4 cpu with all that SM stuff and... booted fine!
Maybe P4 board is ignoring PWR_OK signal and just continue POSTing ?

EDIT:
One additional thing I discovered. In ATX specification (24pin connector) there is one pin NC. While same pin in ATX 20 pin specification has -5V there connected. Consequently my Corsair and Chieftec PSU have empty pin there. While SM PDU has there -5V populated. Maybe modern third party moderboards refuse to boot because of that pin?

EDIT:
I removed both pins and nothing changed, Corsair PSU still successfully boots Asus motherboard and SM stuff does not. Other pins in both PSU types are either GND, -12V, 12V, 5V, 3,3V, 5Vstandby and are similar on SM PDU and Corsair PDU.

If the board power consumption was the case then SM PDU wont serve valid voltages I guess. I added graphics card and nothing changed..
 

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jack2020

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Feb 28, 2021
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I have used Tyan uATX server boards in SM chassis. Did not have an issue (SC836, SC826, SC216, SC417), various PDB, and PWS-920P-SQ
Hi.

I noticed that you have the PWS-920P-SQ PSU. How much quieter is it to the standard 920W PSU. From watching some youtube videos, I know that replacing the Chassis fans make a big difference. I was hoping to but the 386 chassis alone and then buy 2 of the 920P-SQ, but seems I can't. Being home use only can't justify buying the chassis with the twin 920W PSU and then buy 2 of the SQ supplies.

Thanks.
 

itronin

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Nov 24, 2018
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I noticed that you have the PWS-920P-SQ PSU. How much quieter is it to the standard 920W PSU.
Beauty is in the eye of the beholder. Same goes for "quiet". I have not listened to a standard 920W PSU so I can't say.
920SQ PSU is relatively quiet compared to say the 801P-R.

However I can't really tell the difference between the 501P-R or the 740P-R or the 920SQ when the servers are running.
Both the of the former are very economical and depending on your power budget they may work for you.

The main differences between what I have read and heard is that the SQ PSU's stop spinning their fans when the server is off, that and I think they use quieter fans.

I suspect the fans in the 501/740 spin slower (different part #'s).
 

Fallen Kell

Member
Mar 10, 2020
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I can state that the 920SQ are really a requirement if you are trying to make these a quite system. In my 846, I initially just did the fan wall replacement and placed new heatsinks with fans on my CPUs, but kept my original power supplies, and this system still produced a lot of noise (even with removing the rear exhaust fans which I really didn't need anymore since there was more than enough back pressure to force the air out).

After replacing the power supplies with 920SQ units, the machine is quieter than my network gear (which makes sense since the network gear uses 40mm fans).