Modding ATX PSU for Multiple Plugpack Replacement

Project: Replace 3 x plugpacks / wallwarts with 1 ATX PSU unit for a small office.

Devices to be powered:

- Synology DS207+ NAS device
- Linksys WRT54G
- TelstraClear Cablemodem

All are 12V devices so we won't need to breakout 5V.  Also all use standard power jacks except the internal pin diameter varies.

The current Synology PSU is rated for < 4A, the WRT54G needs 1A & the cable modem < 1A.  The PSU we will be using is max 14A on 12V1, and 16A on 12V2 with a combined max of 19A.

The client requested a backup standby PSU also be provided in event of a failure,  so we will make identical modifications to 2 identical ATX PSU's with the loom for the units to be powered able to be readily unplugged from one and added to another.

We will also put on 2 LEDs, one supplied by the PG (Power Good) signal off the PU and the other off one of the 12v supply rails.   No real need for these but everyone likes LEDs even normal red ones.


Purchased 2 new Delta ATX PSU 350W Model = GPS-400AB (ASUS certified, nice if is true)


Pluggable 4 pin connector to mount on the PSU(s):

HM3124 Corresponding part for connecting the loom to the PSU (Note ours is the 4 pin version):


Has nice screw terminals for quick addition of additional units to the output loom in the future.  If I was also breaking out 5v I might go for a 6 pin pair of these as required. But not this time.

Finally some bits & pieces we already have on hand:

2 x Red LED
3 x 220R resistors
A piece of vero board approx 20mmx20mm
A potting box 63w 88h 33d

Assorted heatshrink

End Goal for each ATX PSU:

1. The 2 separate 12v supplys broken out to a pluggable connector (The intent being to run the Synology off 1 supply and the remaining units off the other)

2. A LED to indicate 12v available in the breakout (I dont care off which 12v supply of the two)

3. A LED driven by Gray (Power Good)

4. These PSU's have a hard on off switch built in so we don't need to add one ourselves.

5. The output connector is 4 pins, and is in order of pins 1-4: [12v] - [Gnd] - [Gnd] - [12v].  It is assembed on a small piece of Veroboard.  The LEDs mentioned in 2 & 3 above are also on this veroboard.

6. Reasonably tidy when reassembled (to hide the 'orrible 'acked vero).

What we did:

Open the unit up and put the unplugged lid/fan aside for now.

Started by cutting off all the external connectors leaving about 120mm length.

For Gnd & 12V we will breakout  2 wires per connection (gives us twice the copper in the event we load this unit up with additional load devices in the future).

Spare wires will be bundled and wrapped in heat shrink and left inside the PSU in the event we need any differing voltages in the future).

Action taken for each set of coloured wires:

Black (Many wires)= Gnd:

Left 5 wires free and bundled the remainder.

Soldered 2 wires to each of the output Gnd connections on the Veroboard

Yellow (Many wires) = 12v:

Left 2 wires free and bundled the remainder.

Soldered these 2 wires to one of the output 12v on the veroboard

Yellow Black (2 wires) = 12v2 (This PSU has dual 12v supplys, so this is the second set):

Soldered these 2 wires to one of the other output 12v on the veroboard

Red (Many wires) = 5v:

Bundled all

Orange Many wires) = 3.3v:

Left 1 free and bundled the remainder

Blue (1 wire) = -12v:

Bundled the single wire

Purple (1 wire) +5v Standby:

Bundled the single wire 

Brown (1 wire) =Sense power ok (needs to see 3.3v):

Connected to the Orange left out earlier

Green (1 wire) = Turn on (When connected to Gnd):

Connected to the  remaining Black

Gray (1 wire) = Power Good (Outputs 5v when ok)

Connected to a LED on the Veroboard via a 220R resistor


Finally, added another LED to the Vero board between 1 of the 12v outputs and Gnd via 2 x 220R resistors (as was what I had on hand but is slightly low..)

Note that I've intended for the vero board to sit over the hole the normal leads passed out through to give a tidy finish and save me having to cut any holes / slots in the PSU shell.  Thus I have soldered the wires to the veroboard to try to facilitate this (ie fairly close together and on the part of the veroboard where it should sit over the hole once fixed to the case.

Then mount the board with two self adhesive plastic standoffs and then finally some hot glue..

Put the case lid/fan back on (reconnected)

Then cut a slot in a small potting box with a hand sheet metal nibbler and hot glue that on top and we are done.  A bit of trial and error as I had to hack the edges of the veroboard (a bit ugly) to get the potting box to fit nicely as well as a bit of hot glue trimming.  Also the potting box is way too big, but once fixed in place there are no clues as to how empty it really is so no worries there.

Isn't hot glue wonderful.  Sure it flows too much and I always burn at least one finger but...

Rinse & repeat.

For the second unit we will make the spare wires shorter and will also cut a few of the multiple spare wires off at the PSU board just so we don't hinder the air flow as much as the first unit.  However we expect these units to be severely understressed so heat shouldn't be an issue but we may as well learn from each iteration.  Also, now that we know how to mount the vero & potting box we can trim the vero to suit in advance..