• Dell MPS1000/MPS600 as 54v/48v power supply
  • Dell PowerConnect MPS1000/MPS600
    • MPS1000 vs MPS600
    • Vs RPS600 or RPS720
  • Powering the Cisco N540-24Z8Q2C using a Dell MPS1000
    • Why power a Cisco Router with a Dell Power Supply?
    • Notes about Cisco N540-24Z8Q2C and N540-PWR400-D
    • Powering with 24V (..does not work)
    • Powering with positive 48v instead of negative 48v
    • End result and gallery (probably safe!)
  • Specifications for MPS1000 and MPS600
  • Compatibility Information
    • Accessories
      • The original cable
  • Internal Design
  • Connector
    • Current Terminal Considerations
  • Pinout
  • Powering it up, getting 48V or 54V

Dell PowerConnect MPS1000/MPS600

These models are MPS (Modular Power Supplies) for providing DC Power to several models of Dell Networking and Dell PowerConnect switches.

They are also very useful as for providing high DC currents of 54v (MPS1000) or 48v (MPS600) to anything that needs it.

MPS1000 vs MPS600

Everything I say below has only been tested with the MPS1000 and not the MPS600. However, I have every reason to believe the MPS600 looks, acts, and tastes the same as the MPS1000 excepting the differences with voltage and amperage.

Vs RPS600 or RPS720

If you’ve come here to learn about the Dell MPS720, you’re in the wrong place. The MPS720 is a totally different beast that supplies 12V DC.

The good news is that Steve Zazeski has throughly documented the pinout for you already!

Powering the Cisco N540-24Z8Q2C using a Dell MPS1000

Why power a Cisco Router with a Dell Power Supply?

For this project, I needed a way get 40-60V DC at 12A for a Cisco N540-24Z8Q2C which has two N540-PWR-400-D DC power supplies instead of the more convenient N540-PWR400-A AC power supplies.

The reason for this is the AC power supply is upwards of $900 (USD, February 2024) on the used market, while the DC version is only $150. Even with extra cost of a dedicated AC-to-DC converter it is still 1/5th of the cost. In fact, a pair of AC power supplies will easily cost more than the N540-24Z8Q2C router itself!

Notes about Cisco N540-24Z8Q2C and N540-PWR400-D

The N540-PWR400-D (aka DPS-91) power supply lists two different input voltages with two different output voltages.

Using a borrowed AC power supply, I tested the N540 to use an average of 125W.

Powering with 24V (..does not work)

To this end, I first tried to power it using a pair of 24V 10A power supplies, one for each N540-PWR-400-D.

While the router would boot, it would then quickly go in to halted state with the message “24V IS LESS THAN REQUIRED 40V¹”. So even though 24v can technically provide enough wattage to meet demands, the router itself will still barf.

Powering with positive 48v instead of negative 48v

The power supply says it wants negative 48v-60v if you need more watts. While I was considering using a Cisco RPS-3200 which can output -52v when using it with the C3K-PWR-1150WAC power supply. But, instead, I chickened-out because I wasn’t (and still am not) completely sure how to hook up negative power supplies; and especially, since I would have to hack the connector and so I wouldn’t have any convenient + or - labels.

So, the MPS1000/MPS600 outputs positive power, but the N540-PWR400-D says it wants negative, right? But consider this: the screw terminals are the same for +24V or -48V, so it stands to reason it can accept +48V too.

The reason for this is elementary, but still sounds like dark magic to me; whether power is positive or negative depends on the ground (earth) reference. If the earth reference is connected to the negative power rail then you get a negative ground, and if you connect it to the positive rail then you get a positive ground.²

End of the story: yes, you can power the N540-PWR400-D supplies just fine using positive power.

End result and gallery (probably safe!)

While I did use an ATX connector to prove the power supply would work, I wanted the permanent wiring to be a bit more substantial. Something that would let me sleep at night.

The connector is a compatible Minifit plug from Amazon. They don’t say what terminals are included, but after working with them I think they are Molex 5556.

I am following my own advice (see “Current Terminal Considerations”) and using all four power and ground connectors in parallel, two for each Cisco power supply. Each power and ground wire from the Molex connector is crimped to 18awg stranded with a silicone jacket. Then each pair of power/ground is soldered to a pigtail of 14awg primary wire (leftover from another project). Spade connectors are crimped and soldered.³ to the other end of each pigtail.

In contrast, the wiring for the power switch is whatever I could find at the bottom of my toolbox. Since the power switch simply shorts PS_ON to ground and doesn’t carry any current, anything beyond a bent paperclip is sufficient.

Specifications for MPS1000 and MPS600

Compatibility Information

MPS1000

Designed For

• Dell Networking N1524P, N1548P, N2024P, N2048P
• Dell PowerConnect 7024P, 7048P

Compatibility

• Networking C1048P
• PowerSwitch N1500 Series
• PowerSwitch N2000 Series
• PowerSwitch N2024
• PowerSwitch N2024P
• PowerSwitch N2048
• PowerSwitch N2048P

source

Accessories

The original cable

Don’t bother looking for it, you won’t find it unless you are really, really lucky. It was only distributed with the switches themselves and you can’t order it separately from Dell. It doesn’t bear a standard part number.

The best options are A) do a visual grep of eBay for “16 pin cables with screws” or B) make your own using the part numbers I have below. Seriously, making your own is not hard at all, you don’t even need a soldering iron. If you’re in a rush, you don’t even need the correct connector: you can cut the last 4 pins off a standard ATX power supply connector and use that.

Internal Design

Internally, it is a conventional hot-swap power supply with an interposer adapter board. It is manufactured by Delta Electronics, part number DPST-1000DB A .

For similar power supplies (DPS-1001AV and DPA-1500AV), “Connect PS on and PS Kill to ground to power up.” (source)

Image from aansluit gegevens voeding - Zendamateur.COM

Connector

Connector is a 16-pin Molex Mini-Fit Jr, same family as the familiar ATX motherboard connector. Mating molex part numbers include 39012160, 39012165, 1727080016, 1727080116, and 1727081016.

All versions of Mini-Fit Jr. and Mini-Fit Plus Connectors are compatible with each other, including with Mini-Fit TPA2 and Mini-Fit BMI Components, bringing flexibility to the toughest design dilemmas. — Molex

From left to right, with clip on top, the keying is:

   CL
VOOVVOOV
OVVOOVVO

CL = Clip
O  = Square, no chamfer
V  = Both lower corners chamfered

An ATX Power connector can also be used with the last 4 pins removed.

Current Terminal Considerations

When using the 45750-5111 terminals and 18ga wire, the connector is rated at 13A per pin. However, when using the much-more-common 5556 terminals you are limited to 9A per pin.

When planning your connections, remember that the MPS connector has 4 positive and 4 negative pins. So while you could draw 13A over a single pin with a 45750 terminal it would be safer to split that load over 2, 3, or 4 pins. This goes double for 5556 terminals: even though two of them could take the entire 18.5A current of the MPS1000, you would be safer to split it among all 4 pins.

Pinout

                                          ______________
                                         / CLIP IS HERE \
+-----------+-----------+-----------+------------+-----------+-----------+------------+---------+
| (16) ?    | (14) ?    | (12) +48V | (10) +48V  | (8) +48V  | (6) GND   | (4) GND    | (2) GND |
+-----------+-----------+-----------+------------+-----------+-----------+------------+---------+
| (15) ?    | (13) ?    | (11) ?    |  (9) n/c   | (7) +48V  | (5) PS_ON | (3) CSHARE | (1) GND |
+-----------+-----------+-----------+------------+-----------+-----------+------------+---------+

As viewed from front of MPS1000/MPS600

Powering it up, getting 48V or 54V

If you only plug in power the C16 inlet and expect DC power, you’ll be disappointed. The fans will turn on but there’ll be no one home. Just like an ATX power supply, you need to short the PS_ON pin to ground to get DC flowing and to get the “Power OK” and “Fan OK” LEDs come on.

A direct short is enough, you don’t need to use a resistor since the PS_ON pin already goes through R14 on the interposer board.