Disclaimer: This page is about power supplies. You can hurt yourself or burn down buildings working with power supplies. Pay attention to what you are doing and learn the effects of everything we're talking about here. If you don't have full confidence in and understanding of what you are doing, you can make a mistake which can hurt things and you can be hurt. If you read any further, you are taking full responsibility for the results. All of the information presented here could be wrong. You can be killed. You have been warned.
Make sure you install a fuse between the supply and your wiring such that the fuse will go out before your wiring melts or catches fire.
All power supplies capable of running an entire multi-port node also have the ability to source enough energy that you can ignite a house fire.
For instance, if a radio's protection diode shorts, you will have current flowing from the power supply, through all of the wires and connectors and lug-strips between the supply and the radio.
Heat generated can be up to 1200 watts over a very short piece of electronics. Fuse for the limitations of your circuit, not the limitations of the supply! Feel free to use fuses in more than several places.
These pages used to describe a 30Amp LED power supply available from Amazon and other places for around $30. That supply is no longer recommendable. Too many of them have gone wrong. No house fires were caused but bad smells and loud noises have been noticed.
W4RFQ figured out a trivial modification which appears to work most of the time and involves just a surface mount potentiometer swap.
So far all but one of his modified supplies has worked indefinitely both in a couple of node sites and under heavy testing.
The only one that failed failed quietly and immediately and has stayed dead for no known reason. W4RFQ's mod is a little difficult.
W4VU has achieved positive results using the potentiometer swap as well.
I have one of the W4RFQ units on my new 8-port node rack still on my bench. The supply isn't totally acoustically quiet but it is certainly acoustically quieter than your average PC. Definitely better than the LED supply.
The DC connection on mine is made by soldering a lug to the wide edge connector for DC- and for DC+. I then ran the 60-amp DC feed to a large lug strip (make sure it is rated for high current!) and then separately fused three sets of equipment with 25 amp fuses. The point of the fuse is to make sure that no wire is ever made to carry more current than it is designed for. If one of the radios shorts out, you don't want 700 watts of energy to be bringing it to a boil!.
Note that the modification to the HP supply does require some decent soldering and hacking techniques.
If you would like to consult with engineers, machinists and electricians, we have such who are in our group and who read the TARPN yahoo reflector. Send an email to the TARPN yahoo reflector and talk about what you have in mind.
The supply, unmodified, provides 12v at high current to the HP server computer.
Out of the server the supply won't even turn on unless we do some modifications.
Click to enlarge.
The modification needed to make the supply work outside of its normal Server rack are to solder two resisters across pads on the edge card connector. In both cases the resistor value can be from your junk-box and doesn't require a specific value. In the left hand resistor in the photo, between the small pins of the edge connector, the resistor is providing a logic high so the supply thinks it is inserted into its Server rack cage. In the right hand resistor you are drawing some minimum current from the supply so the regulation works and/or it doesn't think the server is broken.
The resistor values are both around 1K, slightly larger values will also work.
Solder the first resistor between the 1st and 4th small pins on the edge connector as shown. Solder the second resistor between the two larger tabs. Now apply power. You should be seeing something around 12volts from the supply.