HP z420 motherboard 18 pin layout

[Thohmas]

Hello,
I have been searching the internet with no luck. Hope someone here can help with this issue. I have a HP z420 system. The HP z420 motherboard has 18 pin connector for the power supply. I'm looking for pin layout of this so that I can change the power supply to a standard ATX PSU. Thanks in advance!

[Anu0512]

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@Thohmas wrote:
Hello,
I have been searching the internet with no luck. Hope someone here can help with this issue. I have a HP z420 system. The HP z420 motherboard has 18 pin connector for the power supply. I'm looking for pin layout of this so that I can change the power supply to a standard ATX PSU. Thanks in advance!

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Use this connector 

https://www.aliexpress.com/item/PSU-ATX-24Pin-to-18Pin-Adapter-Converter-Power-Cable-Cord-for-HP-Z42...

[Dan_WGBU]

Here is the Z420 motherboard P1 connector pinout:

The +12V, -12V, and Ground pins are obvious, the +11V_AUX_PSU is an auxiliary voltage, PSON# is the power switch, pin 16 is a fan PWN signal, and pin9 lets the system know what wattage power supply is installed. 

Note:  The Z420 power supply is desiged to provide several +12V rails to the motherboard.  The motherboard +5V and +3.3V (and others) are created from these +12V rails. 

   ** The +5V pins do not supply power.  They are connected to the motherboard +5V regulator, meaning that the motherboard routes +5V power to the power supply. **

It looks like the adapter that Anu0512 posted only connects the ATX 12V power to the Z420.  Because the Z420 creates other voltages from the +12V rails, an ATX power supply might not have enough +12V power to support a fully configured Z420 system.  FYI. 

[Thohmas]

Thank you! So it seems the adaptor may not be the perfect solution as I have many things connected to the motherboard. So, how should I re-wire the standard 24 pin atx connector to this 18 pin connector? Thank you!

[Anu0512]

Dan_WGBU  Is there any alternatives because nobody is interested in paying hefty amount to HP and plenty of high grade PSU are available in market but unfortunately due to HP restriction in nobody can use other components.

 However I'm using this converter but only one problem is whenever I shutdown the machine, the machine does not ON so I have to keep pressing the test button in PSU to power ON. It looks motherboard holding some kind of static current which need to reset.  

[Dan_WGBU]

As an HP Employee, I cannot recommend using any power supply except the HP supply (I keep repeating this because I have to say it).  However, let me give some high-level hints to keep users from preventing any system damage.  Of course I cannnot give any HP proprietary or unique design infomation.

Power supply rails cannot provide more than 240VA per rail, per UL safety regulations.  Many systems need more than 240VA of +12V, so a high wattage power supply will have multiple +12V rails.  These different rails power different parts of the motherboard. 

On the Z420, CPU and memory are powered from the 6-pin P2 connector. 

The 20-pin P1 power connector has 3 +12V rails, as shown in the diagram I posted earlier. 

     +12V_B powers the motherboard +3.3V and 5V regulators, some auxiliary CPU voltages, and some fans. 

     +12V_S powers some chipset regulators, some other peripheral circuits, and PCI slots 3, 4, and 5.

     +12V_D powers Slots 1 and 2.

ATX supplies are specified by total output (Watts), which include all voltages together, including +5V and +3.3V.  Therefore, the most important specification is the amount of +12V provided by the supply.  The Z420 supply does not provide +5V and +3.3V, so it is important that the +12V_B rail has enough power for these onboard regulators otherwise the system may not power up.  If the other +12V rails do not have enough power, and high-powered PCIe cards are installed in some slots, they might not have enough power and the system could crowbar. 

All this means that the Z420 needs several separate high power +12V rails to work correctly. 

HP Workstations are designed as a total system, to optimize performance.  That is why HP does not use ATX power supplies in these high-end and high-power Workstations. 

[Dan_WGBU]

The Z420 power supply is turned on when pin 8 is driven low by the motherboard circuitry.  If this does not happen, the power supply will not turn on.  

P1 pin 17 is an auxiliary +11V rail, meaning this rail is active whenever the AC power cord is plugged into the system.  If there is no voltage here, the "turn on" circuitry in the Z420 is not powered so the system will not start. 

Edit:  An ATX power supply puts +5VSB (standby = auxiliary) power on pin 9.  The Z420 needs a 11V auxilary voltage.  If this +5VSB is connected to P1 pin 17, it might not be high enough to turn the system on.  (This is an educated guess, I have not tried using an ATX supply on a Z420).  Be careful, connectors are always numbered differently, and sometimes pinouts are shown as a mirror image (I have to look at the keyed/empty pins to get the orientation right)

[MtothaJ]

An additional benefit of using the original HP power supply is that - if you got the plastic air duct cover fitted over the right side RAM banks - it will help suck the hot air from the RAM, through the PSU and out the back of the machine.

I have not yet seen a replacement PSU which would be designed to support this feature - these almost exclusively have an intake from the bottom side.

[Anu0512]

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@Dan_WGBU wrote:

The Z420 power supply is turned on when pin 8 is driven low by the motherboard circuitry.  If this does not happen, the power supply will not turn on.  

P1 pin 17 is an auxiliary +11V rail, meaning this rail is active whenever the AC power cord is plugged into the system.  If there is no voltage here, the "turn on" circuitry in the Z420 is not powered so the system will not start. 

Edit:  An ATX power supply puts +5VSB (standby = auxiliary) power on pin 9.  The Z420 needs a 11V auxilary voltage.  If this +5VSB is connected to P1 pin 17, it might not be high enough to turn the system on.  (This is an educated guess, I have not tried using an ATX supply on a Z420).  Be careful, connectors are always numbered differently, and sometimes pinouts are shown as a mirror image (I have to look at the keyed/empty pins to get the orientation right)

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Ok, I have Corsair Ax 860i PSU, as you mention all the input and output of current & voltage is matching in my opinion. with my PSU. However have a look on Corsair Ax 860i output see if you find any difference in term of current & voltage supply. 

 

[Dan_WGBU]

One difference is the Z420 uses +11V as an auxiliary/aux/standby/sb voltage.  The Corsair supply specs posted use +5V sb = standby/auxiliary/aux.  These sb/aux voltages are usually on whenever the AC power cord is plugged in.  The +5V may not be high enough to power the Z420 onboard regulators.