Blown fuse in Power Supply

Hello reprappers!
I have a bit of an event I would like your opinion on. I have your basic reprap setup; mega and RAMPS 1.4, prusa i3, 12v 30A power supply. Only difference is, I have two fans running in parallel on D9, 40mm on the extruder and 60mm on the electronics. Now, this setup has worked for me for about a month, before which i had only printed with PLA and only needed one fan, but tonight I finished an ABS print, pulled the part off, and went to reheat the extruder and bed. As they began to heat, I homed the axes and noticed that they were going slow and loud. I turned off the heaters, and tried moving again, and they sounded fine. So I turned the heaters back on, and heard a small pop from my power supply. Of course I immediately unplugged everything, having had several power malfunctions in the past*, and began inspection. The printer itself seems fine, nothing burnt or even over-warm. However, opening the power supply revealed a blown fuse. My theory is this: attempting to do everything at once (extruder and bed and fans and motors) drew more current than the power supply could handle and blew the fuse. Does this sound about right, or should I suspect more than just a blown fuse in my power supply?
I'll have new fuses later this week, and I intend to try replacing the blown fuse before buying a new power supply.

*(my old power supply (12v 20A) spontaneously failed on me one day, taking the D8 mosfet with it. I wasn't even printing at the time. I just smelled smoke and turned in time to hear my power supply make a horrible buzzing sound. still not sure what happened to that. I upgraded from 20A to 30A, but then this.)

You can try a new fuse, but obviously, your machine is taking too much power for the supply to handle. I'd get a separate supply to run the bed heater.

Are you using one of the cheap "LED supplies" from Ebay? Did the fan in the supply turn on before the fuse blew? My experience with those supplies is that if the fan is turning on, the supply isn't going to last much longer.

This is the power supply I'm using. The fan is on constantly when the power supply is plugged in, and kicks on high every time one of the heaters is on.

Right, so I got replacement fuses of the same rating at the one that blew, and swapped one in. Upon plugging into the outlet, with no load on the power supply, an even bigger, louder pop occurred.The new fuse checks out fine, so something else went bad. So, not just the fuse then. darn. Guess i'm buying a new power supply.
So changing the topic; what kind of power supply would you suggest?

Your main choices are:

1. A PSU similar to the one that has just failed on you. The advantages of these are:

- They are inexpensive, maybe even lower than the Amazon price if you get them on eBay.
- They are quiet. I have been using the 25A model in the same or a similar range for nearly a year, and it is fanless and silent.
- They don't need minimum loads on other outputs, unlike ATX PSUs.
- You can adjust the voltage on them, which is useful if your heated bed is underpowered when running from 12V.

2. A similar type of PSU but with a good brand name. You can get these from the usual electronic component distributors. In the USA this would be Newark, Digikey, Mouser etc. They will cost a lot more. Whether they are more reliable, I cannot say. In the USA, I believe you can also buy Meanwell PSUs, which some people are using to power 3D printers.

3. A cheap ATX PSU. I don't recommend these because when used to power a 3D printer (i.e. with a varying load on the 12V rail and little or no load on the 5V rail), they will provide somewhat less than 12V.

4. A good brand ATX PSU, such as the Corsair CX430M which I used for a while to power my printer. You will need to put a minimum load on the 5V and 12V rails, and the output is not adjustable.

The fact is, switching PSUs contain some highly-stressed components, and they do fail sometimes. Typically, the main switching transistor goes short-circuit.That's why they have a fuse. The better brands may or may not fail less often than the cheaper ones. ATX power supplies in PCs fail sometimes, especially in conditions of high humidity where condensation can occur in the PSU while it is turned off (I should know, I have replaced ATX PSUs in other people's PCs quite a few times).

It's also possible that there is a short in your printer somewhere that has overloaded the PSU and contributed to its failure.

Edited 3 time(s). Last edit at 02/08/2015 04:08PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

It depends on what you want to do and what your budget is like. If you want reliable, get or build a simple, unregulated 12-24V supply. The only parts that need regulated supply voltage are fed by a 5V regulator on the Arduino board. You don't need regulation for bed heaters, motor drivers, or motors. An unregulated supply will be reliable, but heavy due to the power transformer.

Try something like this: [www.herbach.com]

Otherwise, look for another switcher, and maybe a spare to keep handy for when it dies.

Switching power supplies and motors are not generally a good mix. When motors operate they produce a back emf that can be a multiple of the drive voltage. If the power supply can't handle the back emf things die. Yes, I know, everyone uses switch mode power supplies.

Edited 1 time(s). Last edit at 02/09/2015 08:12AM by the_digital_dentist.