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Convert other server power supply for RC use

The following article is nothing more than a project report. I take no responsibility for how others may use this information. 

After my success with the HP power supply (PS), I started a search for other models. That lead me to this Dell unit. I grabbed a pair to play with and this is what I have found.
The Dell 700W units (model NPS-700AB)
Doing some research, I found out that these PS units come out of the Dell PowerEdge 2850 series servers. They are larger than the HP DPS-600PB PS and the fan is much louder but they do offer a few benefits over the HP, including 125W more output, better cooling and an output that is slightly adjustable.

Notes, annoyances and updates
  • I found out that the only way to fully remove the latch mechanism is to cut off the mount from one side of the case, so I just left it there.
  • The fan in these units is very aggressive. It does a great job of keeping the unit cool but it is not temperature controlled, so it is very, very loud.
  • There is no fan shield and this fan is not of the friendly type, so lets just say I am keeping my finger clear of it. I might install a 60mm wire fan shield if it becomes a problem.
  • I found out that this PS has a fine voltage adjustment pot inside the unit. I measured an initial voltage output of 12.18V, and found that I could adjust it from about 11.3V-12.9V.
  • In testing, these units have APFC (as I believe most server units do). Under a 10A load my Kill-A-Watt reported the PF as a perfect 1.
  • In my travels I found out that there are 2 models of this unit, one with a small label like the ones I got and one that has a much larger label. The units appear interchangeable in terms of powering a server but they have much different internals.
Photos
Dell NPS-700AB


The business ends. Wow no fan shield!




The important pins.

Mods complete.

12V output voltage adjustment pot.
Turn CCW to increase voltage.


The Dell 550W units (model AA23300)
When I was researching other units I came across these 550W models but passed on them. After receiving the 700W models and finding out just how freaking loud they are, I thought I would try a pair of these. These small units are used in PowerEdge 1850 series servers. They have the same hot-swap plug as the NPS-700AB units and so far it seems to be wired the same.

I took the units, modified them to work outside the server and intended to wire them in series. I opened up one and found out how the DC ground was connected to the case. Turns out it is only connected with one screw but I saw no easy way to disconnect it at the board. I used some heat shrink and a paper spacer to isolate it and that did the trick. I then attached them together and wired them in series, and that is what is pictured below.

Notes, annoyances and updates
  • The latch mechanism is buried in the unit. It looks to be attached like the HP 575W models but I didn't want to take it that far apart to find out. Instead I just zip-tied the handle down to pull the catches in.
  • The fan are not too bad. Yes there are 2 stacked. I have not loaded it yet but I think they might be temp controlled. Time will tell.
  • I did test for APFC and they do have it.
Photos








A nicely finished unit

Wrapped in 100mm Turnigy shrink wrap

1/8" neoprene foam on the bottom


10awg wire series connection and 4mm bullets soldered
directly to output spades, both 24V and 12V outputs