Server Power Supply

12V 75A 1200W HP Server Power Supply conversion for ham radio use

I picked up from a local reseller an HP 1200W Server Power Supply for about CAD$25 (that is around USD$17, in the photo is the unit at the bottom.)

In the picture I included a Chinese switching power supply that I purchased from Amazon for size comparison. The Chinese power supply is rated at 12V 30A and it cost me around CAD$35 (In the photo is the unit at the top.)

The exact model is HP Proliant G6 G7 Power 1200W 490594-001 500172-B21 438203-001 HSTNS-PL11 and I found online that it was somewhat easy to convert the unit for ham radio use and get a whopping 75A


  • 100V input 12V output at 66.7A

  • 110/120V input 12V output at 75A

  • 200/240V input 12v output at 100A

In order to start the power supply I had to solder a jumper between the pin #1 and the pin #4 (left to right.) For some other versions of the power supply I read in some places that a pull up resistor between the same two pins could also be used to start the power supply.

The default voltage without any modifications was 12.32 volts.

In my version of the controller board there was 5 potentiometers similar to the one in the picture. Depending on the exact model of the board this potentiometer could be located by itself (like in my case) or in a row of three beside other two potentiometers.

After cranking the pot all the way counterclockwise I was able to obtain a maximum of 12.68V and I was not very happy about it.

I continued the research and I found thanks to a comment on a YouTube video, that there are two tiny chip resistors. One is marked 01A or 100 ohm and one is marked 01B or 1K ohm. If you short out the 100 ohm (that one is the closer to the top left corner of the rectangle painted around the potentiometer), it will give you 13.2V under load. To the right of the potentiometer the picture is showing you will find a SMD marked 01A. Remove the SMD resistor and jump the two pads it was soldered to. Being very careful adjust the potentiometer next to the SMD resistor you remover until you get 13.8 or as close as you can.

In my case, after moving again the potentiometer all the way counterclockwise, I was able to obtain 13.68V with no load.

That is a nice increase from the original 12.32V as it come originally set.

At later time I found out that the maximum voltage is 13.2V, otherwise the power supply shutdowns itself due to the built-in "over-voltage" protection.

This is the size of the 100 ohms resistor that I replaced with a jumper wire.

You need a good vision and steady hands. Not to mention the right tools.

You can find more information in this site:

There are also lots of videos in YouTube with various modifications and use adaptations.

<- Added the DC power connections.

Added the DC power cable
to the FT-857D ->

Final test

HP Power supply feeding the Yaesu FT-857D and showing 100W RF power output into a Dummy Load.