3D Printer PSU Repair

Finally i get around to another blogpost (tried it with video, not my thing. much easier to just take some pics and write text). I recently aquired a 3D printer kit. For those that dont know what that is: you have to build the whole printer from parts. Its a Geeetech Prusa I3 Pro <some letter, but i dont know which>. Now after painstakingly putting this thing together piece by piece, i even got it to work. But as expected there were problems.

The most obvious one was that i had underextrusion. The printer came with a 0.3mm nozzle, which was just too small for fast printing. So i went and bought myself a 0.4mm one, which now works.

While angrily leveling the bed and doing test prints over and over, i accidentally bumped the printer a bit, and its power went off. Damn, lets see if it works again later. *click*... *click click click* nope. The only thing i got was some coilwhine from the PSU. So i removed the screws that were holding the psu on the printer and let it rather forcefully land on the table the printer was sitting on.

Before disconnecting it, i decided to test it once again. *click*... and the printer came back to life. As it was now running again, i decided to not tinker with the PSU yet. Mostly because of laziness and wanting to do other stuff.

As im now approaching the point, that i got the hang of printing, i want to move it elsewhere. Cant have a loud 3D printer next to my bed when i have to print bigger parts. Before doing that, i decided to take a look at the PSU, to see if i can find a dry solderjoint. Here some pictures

seems the layout is kinda standard for these chinese PSUs. I think its mirrored though, in comparison to the one from previous posts. So we start at the left top.

You see a fuse, a cap, a common mode choke, then a rectifier, a switch to set 110V or 220V, then a really huge ceramic capacitor (big red) it looks like one of those standard ceramic caps, just much wider, then we have the 2 big elcos, at the end of the board the 2 switching transistors, in front of that the whole switching circuit, then in the middle the big switching transformer, to the bottom of that the shottky diode for rectification of the transformer output, then a big inductor and some output caps.

Now on the underside you see a lot of traces. I was looking for a dry solderjoint. On the top you see that big silvery part, that is the pad that leads from the diode to the inductor, and here is where the fault lies. When you zoom in, you can see that the 2 wires of the inductor have broken loose from the solder.

That is a relatively easy fix. So i put some more solder on the part and made sure to burn my fingers on the hot wire while holding the inductor from the other side get the two wires to properly connect to the pad.

Properly might be an overstatement, but i put it back on the printer and it works fine now :D