Following the successful repair of the MML144-200 2m Amp, and needing a high current stabilised power supply to feed it, I cannot thank Len, GM0ONX enough for putting me on to this server power supply.

Designed to run 24/7/365 for 7 years without maintenance, and provide up to 63A continuous current output at 12v, you would think that you couldn’t afford one – especially as it says HP on the rating plate.

Think again.

These power supplies are switch mode units, and as such are generally avoided like the plague for radio use. However, this model for me at least is RF quiet on the bands I operate.

The best part is I purchased two guaranteed working used units from eBay (12th Feb 2021) for £15 delivered – that was for both of them! £7.50 each. Significantly cheaper than a new desktop PSU from one of the radio suppliers.

HP server PSU

Very important: – Make sure the model number is this:

HP ProLiant DL360 G6 750W Power Supply (HSTNS-PD18 version)

Google or Youtube will provide loads of information on modifying server power units.

This post only applies to the model shown above.

There are a couple of very simple mods to do to them before you can use them.

  1. Power on mod
  2. Variable voltage mod

As these are designed to be installed in a server you will need to bypass the server start up and monitoring system.

On the edge connector solder a jumper between the first pin and the ground tab (shown by the yellow wire)- you can also add a switch if you want to, or as soon as power is applied the device will turn on.

Next add a 22k resistor as shown below (between pins 4th from the left and 5th from the left)

Jumper first pin to Ground (-Ve) and a 22k resistor between 4 + 5 as shown

Connecting power will start the power supply, you should see 12v on the edge connector (polarity as shown with the black and red croc clip)

The next job is to mod the regulator to allow adjustment to 13+ Volts.

Add a 22k resistor between the left leg of the potentiometer, and the fourth pin from the right on the vertical board as shown below.

22k Resistor, heatshrink protected from 4th pin to left leg of pot

Connect the power and adjust the pot to the desired output, in my case 13.6v.

On my examples, at 13.8v the protection circuits can kick in and shut things down on switch on. When backed off to 13.6v the system was happy.

Place the insulating shield back into position, screw down the covers and you are good to go.

Both units worked first time, I now have a capacity of 100A plus if needed for less than £20.

A case, meters, fuse holders, and power pole chassis sockets are on order ready to box up the units, more on this shortly.