Need Help Converting a Single Rail Haswell-Compatible ATX PSU for Use with a 3D Printer

Thread Starter

Manbearpig

Joined Oct 30, 2014
10
I got an Anet A8 (Prusa i3 clone) 3D printer and I'm taking as many safety precautions as possible, such as replacing high current wires with larger silicone wire and soldering them directly to the PCB, and replacing the PSU. Some people think the stock PSU is fine and doesn't need to be replaced, but I don't trust it. The caps are made by "Rubicong" haha

I've seen plenty of how-tos on using a computer PSU as a desktop power supply but the ones I found pertained to older or multi-rail PSUs and specified needing a dummy load to function properly, so I'd like to figure out the best method for mine. I got a new 500W EVGA ATX PSU, which is a single rail, and Haswell compatible . My goal is to desolder all of the wires except for a 12v and ground for the 3D printer, and a 12v and ground for some LEDs. I don't think it needs a dummy load but this isn't my specialty so I'd love to get the advice of you pros! What's the best way to go about this? Which outs should I use for the printer? Does anything need to be jumped?

Also, should I replace the CapXon cap with a higher quality one while I've got it open?

Any help is appreciated!


I attached some reference shots but can get some better/specific images if you need them.






 

AlbertHall

Joined Jun 4, 2014
8,785
Power it up. Link the green wire to a black wire (this switches on the main outputs) and see what outputs you get.
If you get no output then you will need a dummy load on the +5V output.

[EDIT] Even if you do get outputs, you may find it collapses if you load only the 12V output in which the dummy load is needed.
 

ian field

Joined Oct 27, 2012
6,539
I got an Anet A8 (Prusa i3 clone) 3D printer and I'm taking as many safety precautions as possible, such as replacing high current wires with larger silicone wire and soldering them directly to the PCB, and replacing the PSU. Some people think the stock PSU is fine and doesn't need to be replaced, but I don't trust it. The caps are made by "Rubicong" haha

I've seen plenty of how-tos on using a computer PSU as a desktop power supply but the ones I found pertained to older or multi-rail PSUs and specified needing a dummy load to function properly, so I'd like to figure out the best method for mine. I got a new 500W EVGA ATX PSU, which is a single rail, and Haswell compatible . My goal is to desolder all of the wires except for a 12v and ground for the 3D printer, and a 12v and ground for some LEDs. I don't think it needs a dummy load but this isn't my specialty so I'd love to get the advice of you pros! What's the best way to go about this? Which outs should I use for the printer? Does anything need to be jumped?

Also, should I replace the CapXon cap with a higher quality one while I've got it open?

Any help is appreciated!


I attached some reference shots but can get some better/specific images if you need them.






There's a (when I opened the packaging) brand new EXGA430 under my desk waiting for me to be bothered checking it for any salvage.

Several good motherboards got junked because I couldn't believe a brand new PSU was the cause of most of the boards not completing boot, and/or random re booting on any that did start. EVGA DGAF; so I've now got a £45 footrest that isn't all that comfortable.

In most cases you have to load both the 3.3 and 5V rails to make the PWM controller to work correctly.

Some cheaper low spec ATX PSUs have less orange wires and give the orange sense wire a pin all to itself. Plugging in to a motherboard commons all the pins that need to be common'ed - off ticket use might not.
The PSU will make an impressive bang if the orange sense wire wanders off on its own.
 

AlbertHall

Joined Jun 4, 2014
8,785
The PSU will make an impressive bang if the orange sense wire wanders off on its own.
I would be surprised if it did. Most will just trip the overvoltage sense and shut down.

Therefore, further to my previous post, if your supply has a brown wire it should be connected to one of the orange wires.
 

ian field

Joined Oct 27, 2012
6,539
I would be surprised if it did. Most will just trip the overvoltage sense and shut down.

Therefore, further to my previous post, if your supply has a brown wire it should be connected to one of the orange wires.
Let me explain in simple terms what happens:-

The sense wire gets separated from the bundle of output wires.

The voltage on the sense wire falls to zero - the PWM thinks there's zero volts on the 3.3V rail and turns the wick up.

The chopper transformer saturates and the transistors go bang.

They usually shatter the encapsulation so badly you can't identify the numbers.
 

Thread Starter

Manbearpig

Joined Oct 30, 2014
10
Power it up. Link the green wire to a black wire (this switches on the main outputs) and see what outputs you get.
If you get no output then you will need a dummy load on the +5V output.

[EDIT] Even if you do get outputs, you may find it collapses if you load only the 12V output in which the dummy load is needed.
Collapsing under no load seems to be a thing with older/group regulated power supplies, and that a single-railed haswell-comptaible, independently regulated one wont have that problem. I think this one is independently regulated but I thought I'd get some more opinions.

I powered it up and get the proper voltage on every wire. Is there a difference between pins 10 and 11? I saw a pinout for a different PSU that said something about a capacitor on pin 10.
 

AlbertHall

Joined Jun 4, 2014
8,785
The PCI-E power lead may include a capacitor to reduce noise from graphics cards (though why it isn't part of either the PSU or graphics card is anyone's guess).
 

ian field

Joined Oct 27, 2012
6,539
I got an Anet A8 (Prusa i3 clone) 3D printer and I'm taking as many safety precautions as possible, such as replacing high current wires with larger silicone wire and soldering them directly to the PCB, and replacing the PSU. Some people think the stock PSU is fine and doesn't need to be replaced, but I don't trust it. The caps are made by "Rubicong" haha

I've seen plenty of how-tos on using a computer PSU as a desktop power supply but the ones I found pertained to older or multi-rail PSUs and specified needing a dummy load to function properly, so I'd like to figure out the best method for mine. I got a new 500W EVGA ATX PSU, which is a single rail, and Haswell compatible . My goal is to desolder all of the wires except for a 12v and ground for the 3D printer, and a 12v and ground for some LEDs. I don't think it needs a dummy load but this isn't my specialty so I'd love to get the advice of you pros! What's the best way to go about this? Which outs should I use for the printer? Does anything need to be jumped?



Also, should I replace the CapXon cap with a higher quality one while I've got it open?

Any help is appreciated!


I attached some reference shots but can get some better/specific images if you need them.






Someone gave me a HP DPS-320NB-1A PSU - according to the label; it has 2x 16A 12V outputs.

As yet - I haven't researched the pin arrangement or what conditions have to be met to fire it up.
 
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