So my printer has been running perfectly happy for almost a year now, about a week ago I smelled a bit of burning plastic, and started to get warnings that Drivers 0,1,2,3,4 were over temperature and the print would come to a complete halt. I figured I would check the wiring and ensure there were no problems. Well, I was shocked when I detached the ATX PSU and found the 12v lines on the breakout board charred. Upon detaching the breakout board from the frame of the printer, the positive 12v lead just fell out of its connector.
To power my printer, I was running from a 450w EVGA ATX PSU into a breakout board, and from there I connected to a 12v->24v Step up converter before feeding 24v power into my duet board. I had seen the warning on the duet wiring guide that all connections should be in crimped ferrules and that you should not use tinned connections. But... I didn't have the equipment to properly crimp the included ferrules, and I figured that if I clamped the screws down hard enough I would be okay. It looks like the step-up converter I used had tinned ends though. It's my belief that over time the connection was heated by the high currents passing through and the solder or tinning began to run. As the solder began to run, the connection became poorer and the resistance increased. Eventually, the connection failed.
To repair the problem I ordered a ferrule set with crimps and reseated all of my screw terminal connections on the printer. I replaced the breakout board, and I cleaned the contacts on the ATX connector.
This week, however, I have run into a problem with the new breakout board burning out as well.
I don't want to keep throwing parts at the problem and I want to get to the bottom of what is going on so I had a few questions for people who are more knowledgable than myself.
The first thing I want to do is ensure there are no shorts anywhere in my system. To do this I was planning to use my multi-meter to check the power lines coming off the duet mainboard. Specifically, I was planning to check the hotend heater cartridge, and the hotbed by checking the resistance across them from their wires that currently connect to my duet. Do you think just checking resistance will work? Do you have any idea what resistance I should be expecting? (E3d high precision 24v 40W and Anycubic 43188-247109 12v/24v ultrabase and heated) Obviously I expect to find some resistance and no resistance would imply a short, but what I mean is, do I need a particular resistance to be confident there is no short?
Next, I plan to replace the breakout board again, and I am concerned the step up converter may have been damaged in the first incident. If so my guess is that there may be a short or problem with the step up converter that caused the second problem. Do you know if there is any way I can safely test the step up converter?
Lastly I was wondering if there is any way that I can check to see if the ATX PSU needs to be replaced? or if the connections might still be okay. The 5v line is still working and the duet can power up, but I cannot turn "on" the power from the web interface anymore, which is probably cause the 12v power line has a charred connection. (I realized there was a problem with the power again when I saw that the web interface listed the vin as 1.7v and had the red off icon indicating the psu was turned off. I tried to turn on the PSU and when it wouldn't do so inspected the connection and found the second problem.)
p.s. I want to mention that I do have a smoke detector mounted above the 3d printer, and especially with covid, I am almost always in the same room as the printer.