hat bed does not work

[sonra]

Hi guys
I bought a second hand M2 printer pre assembled and start to learn how to use it . I try the motors and extrude and they work but the bed heat does not work any idea what can check from electric side ??

[Dale Reed]

sonra,

How are you with a multimeter (volt/ohmmeter)? If you're pretty handy with it, you can check all sorts of stuff.

Need to know a bit about your machine first, though:

1. Does your M2 have one power supply (24 volts), or two "large computer bricks" (one will be 12 volts, for the bed heater, and the other will be 19 volts, for everything else)?
2. Open up the electronics enclosure on the printer and look at the circuit board (the "RAMBo board"). Near the left rear is a 6-pin black connector. Pull the connector and inspect the two pins nearest the left side of the printer. Are they burned / corroded or shiny? These two pins are where the power for the bed heater connects. Plug the six-pin connector back into the board, turn on the power, and measure the voltage at the two screws nearest the left side of the printer. Should read 12 volts (for older the dual supply M2) or 24 volts (for the newer single supply units).
3. Look near that connector, just forward of the two pins you just tested. There will either be a yellow molded component or a blue automotive fuse. This is the fuse for the bed power. Not sure what to do for the older yellow molded fuse, but for the newer boards using the automotive fuse, pull the fuse and inspect it (or measure its resistance). If it looks blown or measures open with the ohmmeter, replace the fuse.
4. Be sure all the connectors for the wiring harness are plugged firmly into the pins on the RAMBo, especially the ones for "HEAT0" and "HEAT1" -- these are the connections for the extruder heater and the bed heater.
5. Inspect the connections to the bed heater at the back of the bed. There is a little black connector for the thermistor (which reads the bed temperature) and a large red connector for the current to the bed heater itself. If the bed temperature reads ZERO in your software, the thermistor circuit is open, and the firmware will not try to heat the bed because there's no valid temperature reading. If the bed temperature reads room temperature (20-ish degrees C), then the thermistor circuit is almost certainly good. Peel open the black loom around these wires and inspect the connections on the red connector. The motion of the bed makes the wires flex here, and it's common for one of the wires to break off the red connector from the constant flexing. (Mine did this, and I replaced the red connector with Anderson PowerPole connectors, rated for 30 amps, and spliced in some "superflex" wire.)

Hope those items help you find the problem. If not, jump back in here and we'll look at some less-likely causes!
Dale

[sonra]

Hi
Thanks for help
the problem was the unplugged connector on the wire from the control box to the heat bed