Page 1 of 1

Dont plug your heatbed into connector for extruder 2!

Posted: Wed May 24, 2017 5:05 pm
by george
Recently the heatbed of my Geeetech G2S Pro didn't warm up. As the printer is built for dual extrusion with two hotends and I only use one I thought it is smart to connect the heatbed to the connector for the second hotend.

Turns out this wasn't the best decision because after some printing there was a strange smell and the printer stopped printing. As I investigated the issue i realised that normally the heatbed-circuit on the board has (and should have!) its own two cables from the power supply and its own fuse. So because the power for both extruder and heatbed came through one cable the power connector of the board melted and the connector was stuck:

(Click for full resolution)
Image

I now desoldered the connector and want to replace the two fuses. The power connector is the only thing on the board which doesn't look fine.
Image

As of now I cannot find my multimeter to check if the fuses are still ok or already broke.
But now to the questions: Shouldn't the fuses brake and prevent the cable to start melting/burning? Can I visually distinguish a broken fuse?
Is my whole assumption right, that the heatbed has its own circuit and fuse on the board?
And most important: Do you think the board will still work if i replace the fuses and the connector?

Re: Dont plug your heatbed into connector for extruder 2!

Posted: Wed May 24, 2017 5:19 pm
by Thomas
1. No, fuses protect the board (which i think they did) not the wiring going to it.
2. No you canĀ“t reliably tell visibly if a fuse is burnt of these specific ones. There are "clear" ones where you normally can see a melted wire but even they can melt on a not so visible place. So always check with a multimeter to be sure.
3. Yes the power part from the heatbed is somewhat seperated from the rest of the board, some boards even have a specific supply only for the heatbed because of the high current a heatbed can consume.
4. i think it will work, but there is always a chance that there is more defect then what at first meets the eye.

Check the fuses, check the power supply and after that you will almost have no other choice then to power it up and hope for the best.

Re: Dont plug your heatbed into connector for extruder 2!

Posted: Wed May 24, 2017 5:31 pm
by PartTimeRonin
Should still work, you probably just overloaded the connectors.

Re: Dont plug your heatbed into connector for extruder 2!

Posted: Fri May 26, 2017 3:39 pm
by kr15_uk
I'd definitely check your heated bed, might be it's out of spec and was the cause.
Simply check resistance between both wires with multimeter, shouldn't be less than 1.2ohm (thats 10A on 12v)

Re: Dont plug your heatbed into connector for extruder 2!

Posted: Thu Jun 01, 2017 1:38 pm
by george
edit: I forgot to reset the firmware and thought the heated bed is still broken but it isn't! Plugged everything into its port and uploaded the old firmware and the heated bed warms up!

Thanks a lot for all your help.

Resistance between the two heated bed wires is 0.9 ohm. Is that too low?