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HP Recommended
xw9400 workstaion
Ubuntu LTS

Power button not powering on, but powers by reattaching power cable, no video

I have tried a different monitor, No joy. only powers on but removing the power cable for a few seconds and reattaching, but no video output.

I tried a different PCIe video card, but no joy

I have checked the new 3 volt battery, it is @ 3.1v and replaced it with a new one.

I have used the crisis recovery jumper, no joy.

There are no beeps or LED errors and the

The power supply LED is green when powered on (BIST*).

I have checked the power supply voltages to the Nvidia dual DVI card and if P6 is detached I do get Beep Error.

I have reseated the RAM (32Gb), and tried different combinations of less RAM, no joy

Power supply BIST* LED lights work with all connectors disconnected

Power supply BIST* LED lights work with all connectors connected; connecting power cord unit fan come on, BIST LED green, but no video

Power button held for four seconds power downs the unit, but then the BIST LED is no longer on and power button will not turn unit back on. Have to remove power cord and reinsert to get green BIST LED, unit powers up but no video.

I have held the power button for more then a few second without the power cord, but no joy.

The 24-Pin Main power connector pin out dose not seem to correspond: pin 12 +3.3 V and pin 23 +5 V is missing or blank

There is no info I can find about the motherboard standby connections. Most motherboards supply either 5v or 3.3v standby voltage to power up the unit, but I seem to loose this once powers down. I didn’t know what pin this would be on the motherboard?

All the power supply connector pins seem to have the correct voltages.

Also the HP repair listing is very much outdated

4-Pin power (memory system board) connector all working

8-Pin power (for CPUs and on board regulators) connector all working

6-Pin power (auxiliary PCI Express) all working

Additional, since this is a water cooled xw9400 with 8 core opteron's this has the DPS-1050CB (1050Watt) higher power supply # 4408608-001

In NC any repair shops are a 4 hour drive from me so I am on my own, and I never got a call back

I would like to find the failed circuit and replace the parts as I have the skills and the SMD re-work station,but I would rather not do hit and miss

I did find three 820uF 6.3v electrolytic's that were deformed on the heads, but replacing them did not help

I have ordered two motherboards, one from china, but only found 1 in the USA, seems all the PCB's are in china!

I love this machine and am not impressed with the new ones

James P Niland IV
HP Recommended

read HP xw9400 service manual fully:




did the power supply light come on when all leads were disconnected (note that "ALL" means all, not most or almost all)

and power was applied to the pwr supply?


if pwr supply passes bist test, remove all cards except for vid card and remove all ram except for minimum config


leave monitor and all other items like drives.usb devices mouse/kbd disconnected


reconnect power supply to motherboard, make sure the aux ram power is connected and is the correct plug, i've seen people try to use a GPU aux connector for ram power and vice versa


power on system, what happens?

HP Recommended

Please define about the BIST* LED. Not getting an absolute from the manual.

The BIST* LED is green when connecting the power cord, but however if I hold the power button for 4 seconds the unit powers down and the BIST* LED is no longer on. So is the BIST* LED always supposed to stay green any time the PS is connected to the power cable?

Before making any post I have often referred to the "HP xw9400 Reference Manual (221 pages)1010902951.pdf", however there is so much there maybe I missed something?

I am expecting one of the 24 pin connector pins to supply something like stand-by power. My understanding is this would be needed to turn the PS on fully, but not of the labelling in the manual actually says standby power.

The section I believe you are referring to is page 135 and in the "HP xw9400 Workstation Service and Technical Reference Guide.pdf", the 24-Pin Main power connector not sure what "V-Rsense" actually means? am I concerned about pin 22, 16 or 13 that feeds the power button?  what is Pin 8 POK? and pin 16 PS_ON_L? Pin 16 has no voltage?

Pins 4, 12, 18 and 23 have no wire?

1 +3.3 V

2 +3.3 V


14 -12 V

21 +5 V
2 +3.3 V

9 +5 Vaux

15 GND

22 +5 V/+5 V-Rsense

10 +12V-B

16 PS_ON_L

23 +5 V
4 +5 V

11 +12V-B

17 GND

24 GND

12 +3.3 V

18 GND

6 +5 V

13 +3.3 V/+3.3 V-Rsense

19 GND


I cannot find a pin-out for J34, Front panel connector 

For the PS with all power connectors disconnected the BIST and fan are working, so the assumption is the PS is OK. As far ass the connector for the video card it is black while all others are white and is clearly is marked P6.

Perhaps the next assumption would be the motherboard, but without a schematic component repair is impossible. Seems China is refurbishing the motherboards and any USA suppliers seem to be get theirs from China.

I have got to get ready for the tropical storm to hit Thursday, so have a good day. I expect to loose internet there after 🙂

Thanks James

James P Niland IV
† The opinions expressed above are the personal opinions of the authors, not of HP. By using this site, you accept the <a href="https://www8.hp.com/us/en/terms-of-use.html" class="udrlinesmall">Terms of Use</a> and <a href="/t5/custom/page/page-id/hp.rulespage" class="udrlinesmall"> Rules of Participation</a>.