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Antec 300-150 400w PSU swap write up / my build info


Junior Member
Mar 27, 2013
Just thought I would share my most recent build and my first ITX...

The biggest part of this was swapping out the guts of the PSUs. Yes, I did find a way to install the Athena PSU without having to swap the guts. BUT, this leaves you with a loud 40mm fan, a huge pain to find a way to properly wire the input power to the PSU, and a negative impact on your cases cooling ability since you are left with a 20mm x 40mm empty space where the rest of your cases exhaust fans are likely to suck air from cooling absolutely nothing.

Right now this is just the info on how to modify the PSU. This is specific to my configuration. If you have different components installed, obviously, you may have to change a few things.

I will follow this up with the rest of the little tweaks I had to make to the case to get everything to fit as well as pictures once I get home.


For now here is my part list:
Antec 300-150 (obviously)

ASRock Z77E-ITX LGA 1155

G.SKILL Sniper Series 16GB (2 x 8GB) DDR3 1866 Model F3-1866C9D

Intel i7-3770S Ivy Bridge 3.1GHz (3.9 Turbo, but I have overclocked it to 4.1)
Prolimatech PRO-SAM17 Samuel 17 CPU Cooler
Arctic Silver 5 (Although, I have seen several tests that show the Prolimatech compound to be superior to Arctic Silver but that was after I had already bought it)

GELID FN-PX08-20 80mm x 2
GELID FN-TX08-20 80mm (inside power supply)
GELID Solutions Slim 12 PL 120mm
GELID CA-PWM 350 mm PWM Y Cable

StarTech Model LSATARND12 12" Latching Round SATA Cable
Monoprice 6-inch SATA Male/Female Extension Cable - Black
Sony Optiarc BC-5550H-01 Slimline Blu-ray
SSD and another 2.5" laptop hard drive I had laying around.
(Going to add an mSATA SSD later)

Video Card:
SAPPHIRE Radeon HD 7750 1GB GDDR5 PCI Express 3.0 x16 Low Profile

Power Supply:
Athena Power AP-MFATX40 400W Mini ITX 80 PLUS BRONZE (warranty very much voided)

ASRock Smart Remote (Power on from ACPI S5 works!)
Xbox 360 Wireless Gaming Receiver for Windows
Custom mini USB port to mount IR Blaster remotely.
Intel Centrino Advanced-N 6230 abgn WiFi + Bluetooth 3.0 (replaced very generic looking ASRock card)


So I guess technically this would be called the Antec 300-400. I took the guts out of the original crappy Antec power supply and replaced it with the guts from the 400 watt AP-MFATX40.

If you know how to solder and at least have basic electrical knowledge then the swap real is not that difficult. But, do the swap at your own risk. These things can still electrocute you after they have been unplugged.

1.) In each power supply, with the c13/c14 cable unplugged, hook up a fan or led or something to any connector that works. Then jump the green wire with any black wire in the 24-pin MB connector to discharge as much voltage from the PSU as possible.

2.) Open up the 4 screws holding the lid on each PSU enclosure. One of them is under a warranty void indicator sticker.

3.) Yay for standards! Each board has the same hole pattern. The only difference is that while the Antec uses all 4 holes the Athena one only uses 3 (because the 4th one covered up by components). Remove all of these and undo the ground wires.

4.) These things are crammed in there pretty well. I used needle nose pliers to undo the wires and power filtering capacitors attached to the back of the c14 receptacle in the Athena PSU enclosure. Only the ground wire was soldered so it was pretty easy. (Save the capacitors for later) It takes some finagling and head scratching but eventually you will be able to remove both of the boards and the fans from their PSU enclosures.

5.) The Athena PSU has way more wires and connectors than you need. I cut the SATA and slim SATA cable off of the Antec PSU and soldered it onto the Athena harness as the Athena harness does not have a mini SATA power plug at all (and the spacing for the plugs is designed to fit in the case already) There are some additional changes you need to make to the slim SATA cable connector for it to fit with my CPU cooler/MB. You have to remove all of the material from the back of the plug to make it about 1/4" shorter with an exacto knife or something like that. This does not affect the integrity of the plug, just the length. I also removed all of the additional plugs and wires that were not needed for my build (PCIE and floppy plugs for example). I also trimmed down the 4 pin molex cable leaving only 1 plug to be used by the PSU fan. There are many ways to rework a wiring harness and everyone has their own opinions on the best way to do it so I am going to assume you are smart enough to figure that part out on your own.

6.) The stock PSU fan sucks. I cut its wires off flush with the circuit board and threw it away. I then removed the metal fan grate built into the Antec PSU case with a pair of side cutters for improved airflow and to make it easier to run the new power and temperature sensor wires for the Gelid fan.

7.) Cut the AC power input cables going into the Antec PSU board. space is tight, so solder the wires to the ones that are now hanging off the Athena PSU board and cover them with heatshrink. Then tuck them in as best you can away from the PSU fan.

8.) The fan wires are routed up and out of the back of the fans housing. Undo the wire routing so that the wires are just hanging out of the motor. I slid the heatshrink and wire sheath down to the fan motor so that the wires would be more protected.

9.) Install the new fan in the Antec housing with the fan blowing out and the wires on the outside of the enclosure through the same hole that the fan is blowing out of.

10.) Install the Athena PSU board into the Antec PSU housing. Remember that you only use 3 of the 4 mounts since the 4th is inaccessible. Make sure you reuse the clear(ish) plastic insulator that surrounds the majority of the Athena board. Also, grab the lid from the Athena PSU.. and look at the inside. There is a clear plastic insulator stuck there. Remove it, and apply it to the lid of the Antec PSU in the appropriate location relative to the end without the fan.

11.) Run the temperature sensor for the fan into the PSU through the same spot where the power goes into it. I left the extra slack outside of the PSU and tucked it away once the PSU was installed. I don't know how much it matters where this sensor is located so I just put in the center of the PSU.

12.) re-install lid.

13.) Now you need to modify the power filtering circuit on the actual case itself. Find that giant brick of heatshrink on the back of the Antec cases C14 receptacle. You can't miss it. Because of some trial an error I did not get this part done as efficiently as I could have. I used a soldering iron that was too hot and damaged the c14 receptacle itself so I ordered a new frontside panel mounted c14 receptacle and started from scratch. If you do it right the first time though you don't need to go through all of that. First slide the large piece of heatshrink back and undo all of the wires (Using a soldering iron I was able to cleanly remove all of the wires without cutting). You can leave the blue X capacitors attached but remove the Y capacitor. (refer to this diagram if you don't know what those are.. http://www.hardwaresecrets.com/imageview.php?image=43919) Now, grab that Y capacitor that you removed from the Athena PSU earlier. Look at how nice it was for Athena to provide a Y capacitor that is already totally covered in heat shrink for you! Solder it on to the hot and neutral pins on the c14 receptacle and bend its legs so that it sits on top of the receptacle. Now, cut the large piece of heatshrink that was original used to cover the back of the c14 receptacle in half. use 3/16th and 1/4" thin heatshrink on the individual power wires and a few inches of half inch on the whole bundle. resolder all of your connections making sure that they go back to the same pins of which they came. Slide all of the heatshrink up covering as much bare metal as possible and apply heat to shrink. I used a few dabs of liquid electrical tape for good measure too. Slide the 1/2" heatshrink up and cover as much of the individual wires as possible and then slide the original large piece that you cut in half up over everything (except for the Y capacitor itself, but it will cover its pre-heatshrinked legs and hold them against the c14 connector). Hit everything with heat again, bend the wires upward and towards the back and secure them with zip ties so that everything is nice and neat and out of the way. The inside of the case now seems 1000x larger. (This is a fact, I measured it.)

14.) Go ahead and plug it in and hope that you don't see any sparks. Jump the Green and Black pins on the 24-pin plug again and make sure that the PSU powers up and the fan starts to spin freely.

15.) When you are done replacing the other crappy stock fan(s) in the Antec case, reinstall the fan housing, and then install your new upgraded PSU.

Also, FYI, to remove and install the PSU you can't have a motherboard installed in the case.

P.S. I still need to proofread this.

Other notes:
COOLER MASTER GeminII M4 CPU cooler WILL NOT fit with this MB/Case combo. (covers PCI slot). Which is fine, because it is also a total piece of crap.