I accidentally shorted the thermocouple with the 24v of the heater cartrige. That burned the the voltage amplifier in the mob for that thermocouple and numerous other components in the mb. I replaced the mb and got 2 new thermocouples for the extruders from maker geek from maker geek. The mounting is the same as the old thermocouple. I don’t know if the bed got messed up when the old mb burned, but that was my assumption that the cap or the thermistor got screwed up. I am not totally sure how they would mess up though since the bed circuit an extruder circuit look to be isolated from each other by what I can see in the mighty board schematic.
Skip to main content
I have loads of parts for these machines if you need any a replacment heated bed di think are around £40 and they are flahsforge style so they read properly straight away and don’t require changing the thermistor, and if you touch any two positive and negitive wires on these machines the board blows as there is no diode back protection
Yeah, that’s how I blew the first mb. I am trying to fix my bed though, are you saying it’s broken beyond repair? Can I test the connection on the connector and see if I am getting proper voltage from the motherboard? Or will this fry my board? I know if the motherboard gets no read from the thermistor it will not turn on the 24v to heat the bed. But there should still be voltage coming into the Bed from the mb into the thermistor circuit.
If you get a thermistor stick it in the red and yellow connector wires on the heated bed connector on the right hand side of the connector and the connect the multimeter to the red and black wires and turn the machine on the bed will read like 150+ °c and turn on the heated bed and that’s the quickest way to measure the voltage
Thanks. I’ll try that tonight and post back.
So I just did this and I got no voltage from the red and black wire. I am guessing that means my motherboard has something wrong.
Was the printer reading the thermistor over what you set it ? I remembered that you have to get it to read below 130°c before the heated bed turns on and I think your board is blown not your new motherboard
I did what you said to connect a thermistor and try and measure the voltage. I got no reading on my meter. I have homed out the bed though sig and ground and I get 57k ohm. It drops in resistance when I heat it and increases when I cool it. That leads me to believe the bed is ok and my mb is not sending out 5v to the bed. I’ll trace it back to the mb and see if it I can get a 5v reading.
Have you checked the wires for any damage but also the 5v source is just for the LED isn’t it? Shouldn’t affect the function of the bed but when you put the thermistor into the connector what did the printer read?
I thought te thermistor circuit ran on 5v, that’s besides the point. I did exactly what you said, I connected a thermistor directly to the connector, red to yellow then I turned on the printer. It still showed NA for temperature. If by doing this is supposed to read 150 then my mb has to have something wrong.
I did this by accident once I switched of the heated bed option in replicator g and forgot and my printer said NA for build platform temp if you plug the machine into rep g flash sailfish on to it and selected bhp installed to yes and plug in your heated bed the. It should read it
This sounds like it could be that. I did flash to sailfish. I’ll try it tonight. Thanks for all the help.
There is no calibration in the firmware for the t/c. It has everything to do with how the eyelet is attached to the heater block. T/c is just accurate, plain and simple. As long as it’s constantly off, treat it as a temperature set point and not an actual temperature ( which really is the truth of the situation ).