Don't try this at home: Power supply mod

kevin-osborn · February 12, 2018

NOTE: THIS PROJECT REQUIRED MESSING WITH HIGH AMPERAGE ELECTRICITY, AND THE DANGER OF FIRE IS HIGH! DO NOT ATTEMPT!!! (Unless you absolutely know what you are doing.)
I have a modified UM2 (olsson, Meduza/Rober feeder, 1.75mm conversion) which has been working well for about 4 years.

A month or so ago, my power supply just stopped working, 0V, no blue light. The printer still worked if I plugged my UM3 PSU in.

I needed to keep printing, and I happened to have a high amp 24V PSU that I'd been saving for a CNC project. After opening the brick and determining that there was nothing I could fix, I removed the output wires/cable, soldered some leads to the end and connected to my power supply.

Mostly because the replacement is pretty expensive, and the new supply was working, I decided not to order a new one.

the only downsides were that the new powersupply wasn't very portable, and was very loud (it has a fan)

During this, @gr5 told me that these supplies sometimes they come back to life when you let them sit over night. Sure enough I plugged the brick back in and it was working again. I didn't trust it enough to reverse my "borrowing" of the cord so I came up with a different solution: install a female barrel jack in the brick, and also on the new power supply. Putting a plug on the cord, I could swap back and forth as I see fit. I designed the adapter in Autodesk Fusion360 (it was pretty simple)

It had to be printed with support on my UM3. BTW, That breakaway material is the bomb!

Speaking of which, my cautionary tale:
I've been cleaning my office and I couldn't find any heavy gauge wire. I decided to snipe some from a pc power supply harness, and well, I should have trusted my instinct, as it looked a little weedy once I stripped it. (thick insulation, but the wires weren't so thick.)

As a result, the first time I powered on, the printer came on fine, but when I drew serious current (bed heating up) by starting a print, the wires vaporized. Fortunately for me nothing caught on fire (though the smoke detectors did go off). I ran to my local electronics store and got some 16 Ga wire. and everything has been running fine.

If you do attempt this, (please don't) I think you should use at least 18 gauge stranded wire. Also, the PCB isn't the greatest quality and it's very easy to lift a trace pulling the original wires out when desoldering.

The design will be up in youmagine https://www.youmagine.com/osbock/designs

Edited February 12, 2018 by kevin-osborn
fix text flow with pictures