Hacking high power switching server power supplies for amateur radio use.




Server power supplies are high-quality, heavy-duty, 24/7 supplies but cheap, less than AU$50. They have been modified for amateur use, particularly to turn them on and to raise the output from 12.2 V to around 13.8 V.

Mobile phone equipment also has such supplies, but at higher voltages, 24, 36, 48, 60 V. These are good for powering transmitters.

As a technique for finding information, Google the power supply model number(s), then look at images or videos for possible sites of interest. Searching images is very powerful and gets past sales sites.

Apparently, many server supplies have additional airflow to keep then cool under load, so additional cooling may be prudent.

A bit of background to the supplies is considered before what I could find for specific models. Some of the links consider RF noise from these switching supplies, something that needs to be considered. Generally, they are high-quality designs with little RF noise, especially compared to laptop supplies, wall warts or common computer ATX supplies.

How much does voltage to an RF amplifier matter?

Should we sweat over 13.8 V rather than the 12.2 V of an unmodified supply? For the RA80H1415M1, an 80 W VHF RF MOSFET Amplifier Module for 12.5-volt mobile radios that operate at 144-148 MHz, the power output per V at maximum output is a bit over 10 W per V. About 15 W between 12.2 V to 13.8 V. Yes, it sounds a fair bit, but does it matter in dB? So, 100 W vs 85 W is 20 dBW  v 19.3 dBW, just 0.7 dBW; undiscernible?!

Common slot power supplies

HP and others have been making hot-swappable, high efficiency, common slot power supplies since about 2003. The supplies are a standard size and all provide about 12.2 V at up to 1000 W or so.

However, the pinouts of the supplies vary. All have 12 V main supply. There may be a secondary 12 V of 2 A for control circuits. Similarly there can be 3 V and 3.3 V for logic circuits. There are a range of control signals I2C bus (SCL, SDA), analog and digital state pins (OK, Fail, etc). All have a pin to turn them on and some have remote voltage sensing, discussed below.

The first task is to be able to turn the supply on, usually shorting two pins, but even that varies. Some supplies can use a breakout board that have an on/off switch, cable connectors and a voltage display. These were used for Bitcoin mining and can be bought for about $10.

The second task is to try to vary the voltage up to around 13.8 V. The simplest way is to fool the remote voltage sense, discussed below, or to find a potentiometer inside the supply to adjust output voltage. Both can be difficult as there are few schematics; but I did find one, see below.


External voltage remote sense hack

The simplest and safest way to increase the output voltage is to fool the voltage remote sense into thinking the output power supply is too low thus increasing the voltage to that desired; 13.8 V rather than 12.2 V normally. Ordinarily, it is used to adjust the voltage for lead resistance.

How remote sense of voltage for a power supply works.

The general approach with the supplies is to short pins 31 and 34 to turn the power supply on. Then connect pin 32 to ground with a resistor to vary the voltage. The process differs a bit between models, so look at the specific model hacks latter in this blog post.


Huge list of computer and server power supplies; full pdf schematics


Connector FCI 10046971-001LF

Warning: These supplies are dangerous when disassembled; live and disconnected. The capacitors have mains voltages.

HP 12 V 1200 W HSTNS-PL11

Very popular for bitcoin mining, but now past the boom. There is an adaptor card available to turn the supply on and to provide a connector to graphics cards or other purposes. It also allows up to four supplies to be used in parallel.

Datasheet for generic 12 V 1200 W similar to HP 1200 W. Gives details on using them and pin-outs.

Application Note for above 12 V 1200 W

Hacking the HP 1200 W to turn on and raise to 13.8 V

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Breakout boards for server power supplies

Breakout boards are available for the server power supplies. They were designed to power multiple graphics cards for Bitcoin mining. The more sophisticated ones detect which model of supply they are connected to as the pinouts vary a bit as noted above. There are a number of different types available. All have 12 V but some have other voltages such as 5 V, if available from the power supply.

Breakout board description and compatible power supply models

Breakout board manual


PCI E 12V 64Pin to 12x 6Pin Power Supply Server Adapter Breakout ...

HP 12 V 1000W DPS-800GB

Powerpoint on hacking DPS-800GB. Shows that the supplies generate little RF noise and how to reduce it even further.

A detailed article on hacking DPS-800GB


DPS-800GB HP 1000W G5 Power Supply | TEC International

HP 12 V 750 W HSTNS-PL18

Hack to turn on and to adjust to 13.8 V. French; use Google translate.

HP 750W Switching Power Supply for DL380 G6 G7 DPS-750RB A 511778 ...

Hacking PC-ATX power supplies

While hacking PC-ATX power supplies is not the main focus of this post, I include some that I have come across or have been suggested by others. It is not a comprehensive list.

Hacking PC-ATX supplies for multiple voltages. Spanish; Google translate works.


  1. This has been super helpful. Thanks!

  2. Who has the voltage adjust and OVP for the other type of 1200w HP supply?


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