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UM2 Power comes on but no servos, no heat - half solved

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This is partly solved.

When I power on my UM2, lights and software comes on but the head won't home, no extruders move, and no heat comes on. The problem is with K1 - it's not closing. If I give the controller board a hard rap with my finger, the relay closes and the UM2 is fine until the next time I power it up.

I will look at K1 more carefully in the future (check solder joints etc.) but right now I am printing something.



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The problem just started after having the printer for a few months. It was a little frustrating because I coincidentally had my first clog which I was able to clean out and fix and continue the print but in my video above there was a print sitting on the glass waiting to continue after 8 hours of successful printing with 20 hours to go...

So I am diagnosing with the printer on the side and the print hanging sideways off the glass and I'm hoping the glass doesn't slip a millimiter in X or Y while it's on it's side and I"m careful not to bump the print. But it all worked out fine and I continued the print flawlessly :)

I have 3 things I want to do with my UM2 as soon as I have some free time. One of them will be to remove the board from the bottom and look at the voltage on K1 coil at power up to see if the problem is K1 or the circuitry driving it.

Actually I can probably probe from the bottom side.

I also want to do some "overhang" tests and some "printing speed" tests.

The printer has me trained - whenever I turn it on I just rap the board, lol.

This is one of those cases where the printer is the boss and has me trained. :)


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Oh and to make the story more exciting - the build plate was at 70C during the print and it keeps shutting off the heater while I'm cleaning the nozzle and I'm scared that if the temp hits 40C or cooler my print will "pop" off the glass so I was kind of rushing (calmly) to get this working and I keep "fixing" it but not sure how I do it and I took the bottom cover off twice before I figured about the relay with the temp going back up to 60C then down to 40C then up to 60C then down to 35C...

I learned a lot about the print head and how amazingly easy it is to service. It helped that I read everyone else's notes about it over the last few months.


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Update - it's definitely K1. The voltage at the coil is 4.9V when it is working and when it is not working. Also the problem only occurs when the relay is warm. So if I leave the UM off for 30 minutes it always powers on perfectly. I can even hear the very fast double click on power on. I turned it off and on 20 times always perfect. But if the UM2 has been on for an hour and I turn it off and on it fails 20X in a row. So I think the coil in K1 was hot. I will order another one. In the meantime this problem is very minor for me.

And before you ask - I have only used this printer in the winter in a cool house so I don't know if this problem will get worse in the summer.


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