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Just last night the heat bed stopped working. It was fine up to 75 % of the print, then when it was done the bed was not on anymore. The display said it was set to 50 °C, but it was at 18 °C. I did try moving the pins, and that is not loose (very simple thing to try).

I want to know what could have happened and what to look for when I try to fix the heat bed.

Please note: I do have a multi-meter. I do not use a MOSFET (I do have plans to install on)

Upon further investigation, I tested the mother board for any voltage were the bed hooks up and there is nothing. I had the printer trying to heat the bed when I was testing. But the thermistor is working, when I unhooked the connection the thermistor went to 0 °C, when plugged in it went to 18 °C.

Is it the motherboard? How can I fix this knowing no power is being supplied to the bed from the motherboard? Do I need a new motherboard?

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  • $\begingroup$ So when you preheat your bed through the menu still nothing happends? $\endgroup$ – Granny Feb 13 '18 at 14:16
  • $\begingroup$ @Granny Correct, I have tried pre-heating, restarting the printer just to see what happens but it still is not heating. It must be a physical thing. The printer does say 50*C when I pre-heat for PLA. Just the bed not heating. The red LED does not even turn on like it should. $\endgroup$ – Ljk2000 Feb 13 '18 at 14:19
  • $\begingroup$ And you are sure all the wiring is still properly connected? On the board and the plug on the heatbed itself? Almost always the plug on the heatbed of the anet printers can burn out. May even cause a fire. Thats why a mosfet for the bed is one of the most recommended mods to do as fast as possible. $\endgroup$ – Granny Feb 13 '18 at 14:20
  • $\begingroup$ @Granny I did make sure the connections are all in place, but I might try directly soldering the wires to the heat bed, maybe that would help? $\endgroup$ – Ljk2000 Feb 13 '18 at 14:22
  • $\begingroup$ Soldering directly to the board is also recommended. But it is not 100% needed (if of course nothing is actually broken on the plug). Just make sure your solder is strong and a good connection is present. If everything is properly connected but its still not working, soldering it to the bed directly is a good next step. $\endgroup$ – Granny Feb 13 '18 at 14:23
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This is a shot in the dark, but the vast majority of problems with a heating bed stopping to work is usually at the cables/connectors interface.

This is because in printers like the A6, the cable/connector is subject to constant mechanical stress, and - since metal fatigue is a thing - either the solder or the cable core cracks.

You should make good use of your tester to verify the integrity of the circuit in the bed and if it is not toasted you should be able to just repair the connection.

For many printers there exist "strain relief mods" to prevent this type of failure to happen. The first one showing up for the A6 is a full chain, but normally is enough the have a small enclosure for the connector like this one for the CR-10.

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  • $\begingroup$ I have seen those strain relief mods, but I had the cable in a way that I thought would keep the stress little to non on the connectors. I might have been wrong not printing the upgrad/mod. I might solder and if that fixes the problem then for sure will print off the upgrade/mod. And thank you for the links, I will be looking at them right away. $\endgroup$ – Ljk2000 Feb 13 '18 at 14:53
  • $\begingroup$ @Ljk2000 If your bed works again and you start printing this strain relief mod. A simple ziptie to one of the bolts that hold the bed down is a simple and quick temporary solution to keep it nice and safe. $\endgroup$ – Granny Feb 13 '18 at 14:55
  • $\begingroup$ @mac Could you look at my little update and perhaps modify your answer? I really need some help on this issue, thank you very much! $\endgroup$ – Ljk2000 Feb 15 '18 at 14:15
  • $\begingroup$ @Ljk2000 - I'd like to help, but I'm not very experienced when it comes to the electronics, the only thing I can think of is checking if your MB is equipped with a fuse for the heating circuit,, and checking that's not blown... $\endgroup$ – mac Feb 15 '18 at 15:43
  • $\begingroup$ @mac Understandable. I did not see a fuse though, never looked for one. $\endgroup$ – Ljk2000 Feb 15 '18 at 16:57
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The bed stopped working yesterday. I used the multimeter on the bed plug. The bed heater reads 1.7-1.8 Ohm.

There was no 12 V supplied from the mainboard and I read its terminals. There were 12 V there. I tightened the screws and the plug received 12 V.

The bed heated for one print. Today I repeated the troubleshooting and found that the bed plug still had 12 V. When I pulled it, the Red terminal was burnt and melted into the plug. After cleaning it by inserting and removing it several times, the bed started working again. The Red and Black wires are hot to touch though.

This is the troubleshooting procedure one should follow. What remains to be confirmed is whether the resistance of the bed heater is correct; 1.8 Ohm at 12 V is about 80 W. Sounds about right, so the wires should not overheat.

I suspected a possibility of the shorting to the aluminum bed, but then the bed would be heated only in some areas, but mine is heated evenly across the entire surface area.

Edit: For now I ended up cutting the Red wire's terminal from the plug and soldering the wire directly to the bed. I might order the new bed harness from Anet, or not.

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  • $\begingroup$ i suspect the plug to be unerengineered. $\endgroup$ – Trish Nov 17 '19 at 22:52
  • $\begingroup$ I agree. The plug uses 1x hot and 1x ground clamp while the bed has 2x each. It should be trivial to add wires between the mainboard and the bed either by adding terminals to the plug, or soldering wires directly to the bed. $\endgroup$ – SuperAl Nov 20 '19 at 2:31

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