Hp server power supply mod.

[BC Coyote]

Be forewarned........the problem with these kinds of switching power supplies isn't regulating the power, it's the fact that most if not all of them radiate enormous amounts of RF crap. I bought a 40amp IOTA supply and immediately sent it back as it created over 5 s units of noise across the band. I eventually bought a Megawatt supply which while perfectly quiet on 11 meters was super noisy on 20 meters and below.
I eventually did what 999 did upthread and mounted the Megawatt inside an old power supply enclosure. I added line filters on both the inputs and outputs to the Megawatt. I added lots and lots and lots of chokes everywhere. I added bypass caps on the ac input and dc outputs to ground. I added a couple of large electrolytics (to stop the supply buzzing on SSB transmit). I connected a heavy guage ground wire from the enclosure to my station ground bus.
After all that I can honestly say it is electrically quiet in terms of interference. But it didn't come easy !

 

[brandon7861]

Be forewarned........the problem with these kinds of switching power supplies isn't regulating the power, it's the fact that most if not all of them radiate enormous amounts of RF crap.

the power supply in question is dead silent. I have two of these units, not a whisper of noise comes out of them. There is a reason these are so popular, price is half of it.

 

[Eldorado828]

Be forewarned........the problem with these kinds of switching power supplies isn't regulating the power, it's the fact that most if not all of them radiate enormous amounts of RF crap. I bought a 40amp IOTA supply and immediately sent it back as it created over 5 s units of noise across the band. I eventually bought a Megawatt supply which while perfectly quiet on 11 meters was super noisy on 20 meters and below.
I eventually did what 999 did upthread and mounted the Megawatt inside an old power supply enclosure. I added line filters on both the inputs and outputs to the Megawatt. I added lots and lots and lots of chokes everywhere. I added bypass caps on the ac input and dc outputs to ground. I added a couple of large electrolytics (to stop the supply buzzing on SSB transmit). I connected a heavy guage ground wire from the enclosure to my station ground bus.
After all that I can honestly say it is electrically quiet in terms of interference. But it didn't come easy !

This isn't one of those iota or powermax converters as I've actually used those before as well without issues.

This is a server power supply and several have report no noise on this specific one, electronically quiet as I'll soon find out for myself.

Voltage is quite a guessing game with these, and amperage will probably be the bigger guessing game.

 

[Eldorado828]

Here she be so far and hopefully it will be of help to someone else.

More to come

 

[BC Coyote]

Nice ! Thanks for the report ! Do you know if those supplies are stackable in the same way the Megawatts are ? Part of the reason I went with Megawatt was the ability to parallel a second supply with the first should I ever need more amperage (unlikely but it's nice to have the option).

 

[brandon7861]

If you intend to run above half the rated amperage, shooting for almost a volt higher is probably a good thing as it will sag a bit from no-load voltage using the usual modification. The one I did was for a friend (and I no longer have it), but I think it dropped over a half volt running an IC-718 at full power. If it is doing 14.4v now, I'd try it that way before attempting to adjust it for a lower voltage. Car alternators range from 14.4v to 14.8v anyhow.

 

[Dr_DX]

Seems familiar:

Anybody use switching power supplies?

You can run any power supply as I have but my power company has so much noise I'm still trying to figure out my self how to eliminate noise

www.worldwidedx.com

 

[jtrouter]

the power supply in question is dead silent. I have two of these units, not a whisper of noise comes out of them. There is a reason these are so popular, price is half of it.

Yes this is true as between myself and friends we have done 5 of these to date and
not a single one caused any birdies at all. Good luck.

 

[unit_399]

Years ago, I started a thread called "100 amp 12 volt power supplies for $20.00" I mentioned that I bought an HP server power supply (12vdc@100A) for $20.00.
Now that BBI (and others) finally woke up and heard about this, it has started a big move to server supplies. As usual, BBI claims that it was his idea. REAL server supplies don't generate RF because their output is checked and monitored by the FCC before they are allowed to go into service, to ensure that their spurious output is below acceptable limits. Over the ensuing years, a lot of so-called "server" supplies have shown up on the market that generate more rf than most of the CB radios that they power. Honest-to-goodness server supplies are manufactured by HP, Dell, Hauwei, IBM, etc. Use them and they will work well w/o generating massive RF noise. Use the fake so-called server supplies, and you won't be happy.

- 399

EDIT: On my base station, I use four (stacked) MEGAWATT S 700-12 Switching supplies @ 14.0 vdc. They power my TX-600 amp to 800+ watts on SSb w/o any added noise. I know the MEGAWATT supplies cost more than a surplus server supply, but they work out of the box. I operate on 26 -28 Mhz. I can't speak for other bands. But on my freqs, I can't ask for more.

 

[Eldorado828]

An update after finally getting back around to this project. Don't laugh at my test bed, I used what I had available from the former car audio days.

The goal is to power the dx500v with this supply but I had the 2970n2 next to me so I'm initially using it to draw off of the server supply. I pushed the n2 really hard at high power in different modes and the supply doesn't even flinch, stayed cool, fan ran slow and voltage drop was only about half a volt while in high power transmit. I wasn't sure how the protection circuit would behave with the resistance values I used but so far so good.

Maybe today I can rig up a radio into the dx500 and put the supply to the intended amp draw.

More to come

 

[Eldorado828]

Final report as far as testing and I'll let this thread take a rest. I may give a reliability report after some time.

I got around to putting the 500v on the supply and driving it both in AM and SSB with the original 5555N (NOT N2) on a separate power supply. The radio is squeaky clean as far as the spectrum goes so take that into consideration. The 500V at 500+ (the meter is relatively close to the cn901hp) pulling hard on the supply and again it never broke a sweat or did anything funny. Voltage drop went from 14.4 to about 14.26, not bad. I romped on it pretty hard, harder than I would on a typical qso and all works pretty good so far. At the same time, the Texas Star is working well also, as this was a moment of testing the supply and amp after that ordeal in another thread.

Considering the supply was about 30 bucks, I have to say that's pretty dog gone good!

End of my report, unless long term doesn't pan out.


Maybe, no more to come

 

[Greg T]

I modded one like this and got it to 14.5v easily. The next one I tried was putting out 15.89 and will not drop. I removed the mod, no change. I removed the factory variable to check it and it was good. Even without the variable in it it is running 15.89. Can't use it. Makes a good paper weight.

 

[Eldorado828]

I modded one like this and got it to 14.5v easily. The next one I tried was putting out 15.89 and will not drop. I removed the mod, no change. I removed the factory variable to check it and it was good. Even without the variable in it it is running 15.89. Can't use it. Makes a good paper weight.

Was it this same model? Maybe it was bad to start with? Not much experience from me, I'm a newbie to these supplies.

 

[Greg T]

Was it this same model? Maybe it was bad to start with? Not much experience from me, I'm a newbie to these supplies.

It's a DPS 1200SB A. Yes, my mistake was not checking the voltage before I did the conversion.

 

[Smokinone]

Did the 750 watt version, PL-18. Jumper-ed the resistor by the pot. Adjusted to 13.85. Works well up to about 15-20 amps, then starts buzzing and cuts off.
I didn't do the Over Voltage part as 13.8 was all I need to go. It doesn't drop hardly at all as far as voltage, just starts to squeal and cuts out. I think I might have got a bad one, I guess there's probably a reason there's so many on the market, probably quite a few out there that were replaced due to not being able to do the 55 to 65 A.
Just a thought, maybe I'll go back in and do the OV part, although I didn't think it would need it as most of what I've seen doesn't require that part of it until going above the 13.8V.
Not a big deal, just thought maybe I'd goof around with one of these for fun, and at $18 I can't kick for just the experience. Maybe I'll drop to 12V and see if it still cuts out.