Printer Suddenly Stopped Responding: Dead Power Supply?

Hi all,
After a few days of my printer finally operating smoothly, it seems I have a new problem. When I went to check on my last print, I found that the printer had frozen about half way through the job. At first I thought it had simply lost the USB connection for some reason during the print, so I killed the print job and tried to move the extruder away from the partial print with the manual controls. To my surprise, the printer did not respond. So I manually moved the bed, removed the print, and tried homing the axes again. Still no response. Next, I disconnected the printer from Repetier and reconnected. It appeared to reconnect normally, but the manual controls still weren't working; I tried moving the print head, turning the fan on, and heating the extruder and bed, none of which produced any reaction from the printer. However, the printer seemed to think that it was working: when I tried homing the axes, the number next to the home button went from a red "0.00" to a black "0.00," and after a brief "1 Commands Waiting," the blue box once again proclaimed "Idle."

I then disconnected and turned off the printer, unplugged the USB cable, and quit Repetier, then turned the printer back on, plugged the USB cable back in (checking both plugs), started up Repetier, and pressed connect. Again, the log showed the normal startup sequence, and attempting to home the axes produced the same result, with no reaction from the printer. When I switched the tab at the top from "3D View" to "Temperature Curve," the temperature graph was stuck.

The next thing I tried was clicking the "Emergency Stop" button in Repetier. The log then showed the startup code again, and the print head coordinated turned red again, but other than that it didn't seem to have changed anything. I tried several more combinations of unplugging the USB cable (swapping it out with a different one didn't help), restarting Repetier, and turning the printer on an off, none of which were successful. Pressing the reset button on the printer (behind the 3 in the Robo 3D logo) turned the zeroes red again.

That's when I though to look underneath the printer. There's a little green LED on the power supply, in the front left corner relative to the front of the printer. This is normally lit up green when the printer is powered on, but now it was off. (I checked the electrical plug, and it was fine. I also checked to make sure that the printer was actually turned on.) A dead power supply would certainly seem to explain my problems: the computer can connect the the Mega2560 board because it's powered through the USB connection, but nothing else on the printer functions. And when I found the printer stuck in the middle of the print, the power supply fan, which had been running pretty much continuously throughout the first part of the print, was not running.

But, Repetier is still getting feedback from the thermistors, and the Temperature curve graph is moving along normally. I'm sure the that the thermistors are working, because when I laid my hand on the print bed for about 30 seconds, the bed temperature at the bottom of the Repetier window went from 25.90 to 26.10, and when I removed my hand, it went back down again. It did this half a dozen times, consistently. So would the temperature reading still work with only USB-supplied power? EDIT: The temperature graph/thermistors still seem to work even when the printer is turned off, but connected to Repetier.

I initially thought that the RAMPS board was the problem, as it controls the motors, but since the power supply LED is out, a problem with the PS seems like the most likely explanation. Is this the problem, and if so, how do I fix it? Do I need to replace the whole PS? Is there anything else that could cause this? Thanks in advance!




NOTE: I recently replaced the Taurino Mega2560 board because it couldn't connect reliably to my computer. I installed a Sainsmart Mega2560, with the same firmware as was on the old board. I have not had any problems with the printer after replacing the board until now.

SPECIFICS:
•Computer: Macbook Pro, OS 10.7.5
•Printer Software: Repetier-Host Mac 0.56
•No powered USB hub
•Printing in ABS with extruder at 205˚C and bed at 80˚C. The failure occurred about 45 minutes into the print.

 

I know this sounds like a cheesy tech support question but, have you shut down and restarted your computer?

 

Yup, twice. Not cheesy, just thorough.

I got out my multimeter and checked a few things in the printer. The power cord is supplying power, and the on/off switch works. But, there didn't seem to be any power where the wires that run from the plug/power switch to the power supply connect. There's three wires, which connect to screw terminals near the back of the power supply, and I tested every combination. I'm not sure which wire is which, since they're blue, purple, and half green/half yellow respectively, but there doesn't seem to be any power between any two of them.
I also checked the wires that go out of the power supply, this time with the multimeter on the 20VDC setting. No combination of the four wires closest to the front of the power supply produced a reading. I also got no reading on the screw terminals where these same wires connect to the RAMPS board; again, I tried every combination.
Lastly, I checked the six wired that run from the RAMPS board to heat bed and to a large bundle of wires that connects the RAMPS board to the motors. Still nothing between any two of them. (I'm assuming that the motors don't run on less that two volts.) And yes, I made sure the multimeter works. Is there anywhere I could test that would locate the source of the problem for sure?
Thanks.

 

A few pictures to clarify:

 

Did you check the fuse in the Switch/Plug module? Pop the door next to the power plug.

 

No, I actually didn't even notice there was a fuse there. That could very well be the problem, though!
This is a bit embarrassing, but I can't figure out of the life of me how to open the fuse cover. Does it have a hinge? Does it just pop off?
Thanks!

 

I figured out the fuse box; it just pulls straight out Here's a picture, in case somebody else has the same problem.


I broke the little tab off on mine, so I had to pry it out with a screwdriver. Maybe I can print a new one that's easier to access, just in case.

A bad fuse would certainly explain why the wires going into the power supply don't have any power. Since I know that the on/off switch works and the wires are all attached, the fuse is the only other possible point of failure between the plug and the power supply unit.

Anyways, the fuse looks intact, but the multimeter says it isn't. The fuse is definitely the problem, and will be replaced shortly. Thank you Steve C!!!

 

Nice! I found about the fuseholder when rewiring for an auto shutoff relay. One thing to note about my switch assembly is that the wire lug crimps were very bad. The Hot wire just pulled right out of the crimp when I was moving it around a bit. I ended up replacing all the lugs.

 

I just got my replacement fuses today, and my printer is now back up and running! Thanks again Steve!

 

I seem to have a similar problem and I am hoping a new fuse will fix it. Thank you very much for your extensive posts and thanks to SteveC for suggesting the fuse. Where did you get your replacement fuse? The fuse in my printer has no markings.

 

My printer's fuse says F5AL250V, probably http://www.ebay.com/itm/like/291085578359?lpid=82
I would check you local harware store Home Depot or an equivalent.

...OK as I wrote this holding the fuse one of the metal endcaps just fell off. Very poor Chinese quality on some of the parts. Looks like I am going to Ace Hardware this afternoon. I swear I didn't make this up!

 

Ouch! At least you found it on you're own instead of failure and a half hour of troubleshooting.
Something like that happened to me last week, I was taking my boys glasses in to have a nose nub pad thing replaced and as I'm literally walking in the door the glasses frame fell in two pieces in my hand. I was like "well at least I'm in the right place lol." took an extra week for a replacement but I was glad it happened at that time I guess.

 

Sorry that should be F5AL250V. It's just not my day.