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My printer started doing something funny recently. I have had little to no issues with power since I built it last November, but recently it started doing something funny. The printer will randomly lose all power - Rambo LCD, PSU fan, everything I think this means its a PSU issue. The problem usually goes like this:

-Printer turns on fine
-Printer heated bed and nozzle heat up fine (I can stay at this point for a long time with no power issues)
-Print begins and during first few minutes suddenly shuts off, sometimes it is part way through the print which is very frustrating!

I can toggle the power switch and its back on, sometimes it can print fine on the next attempt, other times it just keeps doing this. Anyone have recommendations on what to check to verify if it is the PSU or other things to check? What causes the PSU to shut down, could it be an overload of power from a certain source? Are there any error logs or something I can watch to see more information on whats going on, basically monitor the printers vitals during the print.

Your help is very much appreciated!

If it's a power supply issue, it may be overheating, or it may be overloaded. Check that your output voltage isn't too far above 12V, and try leaving the lower panels off the printer.

Is this the ATX supply, or the newer one you're having troubles with as well?

My guess is you have a loose or exposed connection on the hotend wiring, and the movement is causing it to short, this will cause the PSU to shutoff.

It could just be a bad PSU, but it's under the most load when the bed and hotend are heating up and I'd expect it to trip then if that were the care.

Thanks for the input! You guys were right about it being the PSU.

I did a little more investigating and found out my problem. First I tried printing different files, to make sure it wasnt a software issue, really didnt expect a different result and the printer shut down in the first 30s of the print. I noticed the printer never lost power at temperature before the print started, so I tried printing with no filament. To my surprise, it worked fine, the printer moved along for a few minutes and after I was convinced it could proceed without issue I killed the print. Then it clicked in my head, it was much harder to push filament through the hot end than previously, after I did McHackney's nozzle bore modification my E3D could spit out filament like a hose, now it was struggling. After taking apart the hot end, cleaning the heat break and nozzle, I put it back together and once again the filament flowed smoothly. Finally I tried a print and voila, no power shutdown!

So the conclusion:
1) my nozzle was slowly getting clogged over time.
2) This required the stepper motor for the EZ Struder to require more power to push filament through
3) This drew too much power causes the PSU to shut down.

Odd that I didn't have a clog or something, had many clogs in the past getting the E3D to work, and never had the PSU shut down. Nonetheless I have been printing for about ~6 hours now without any issue.