UMO+ print head won't heat up anymore - relay turns off and on

[Umo_Alex 4]

As soon as the printer gets to start heating the printhead (either through starting a print, or going to "prepare=>preheat PLA1") the relay klicks off and then on again.

I've had problems with the connection of the adapter to the printer being a little too loose ever since I've had it, but this seems to be a permanent problem.

 

NB. Not quite new here. Used to be Alex+

[gr5 2,332]

It's probably K1.  That's the only relay.  Here's how I fixed it.  That was in 2014 and it still works great:

 

 

[Umo_Alex 4]

Thanks for the quick reply. I'll try this tomorrow.

 

[Umo_Alex 4]

Tried this but it didnt solve the problem.

 

Mind you, in my case the bed heats fine and the servos work as well.

 

Any other ideas? (anyone 😀)

 

[gr5 2,332]

How do you know a relay is clicking off?

[Umo_Alex 4]

Here's a little video of what's happening: https://youtu.be/N1u-zWsm9f0

 

[gr5 2,332]

okay, your description of the problem was pretty bad, lol.  You took me down the wrong route.  There is nothing wrong with K1.

 

What is happening is your power supply is turning off and on.  The power brick.  This causes your printer to reboot.  It happens quite quickly so I'd guess your heated bed is shorted.  Or maybe your power supply isn't powerful enough.  Was this a UMO upgrade?  When you upgrade you have to use the larger power supply.  Is it possible you are using the weaker power supply and your proper power supply is sitting around unused?

 

You want the 221W supply that can put out 9.1 Amps.

 

Alternatively the power supply may be bad.

 

And finally you may have a short in your heated bed.  Do you have a multimeter?  Do you have a friend who is good with a multimeter?  The bed should be around 4 ohms.  If it's 2 ohms or lower then that's the problem - you have a short.  In fact if it's < 3.8 ohms that could be the problem.  Most likely you have a short and it's 0 ohms.  Shorts are quite easy to fix.  You have to check the wiring.  The most likely two locations would be where the cable connects to the heated bed as that gets some torque and stress.  The second most likely spot is where the power cable connects to the circuit board.  The wires may be touching and shorting out.  On either end of the cable.

[Umo_Alex 4]

Ahaa! I found the culprit. You were (almost) right: There was short in the heater element of the print head (not the heated bed).

Fixed it and it's merrily printing away again. 🙂

 

Thanks!

 

Edited June 25, 2019 by Umo_Alex