Unresolved Heatbed reads 0

Hey Guys,


So I had to replace the heating pad for the heat bed, mine had the wires rub long enough that it exposed wires and quit working. I called and got a replacement from ROBO3D and got it all installed. After installation, I powered everything up to test. MatterControl reads 0 for the heating bed and reads room temperature for the extruder. So I switched the extruder and heat bed pins and I then get a reading for the heat bed (under the extruder temp) and still get a reading of 0 for the heat bed temp (now with the extruder plugged in.) Is it possible that the pins for the THERM1 are donezo? Is it possible to test? Is it possible to move the heat bed to the pins for THERM2?


Any help would be greatly appreciated.

 

It sounds like a bad thermistor on the heated bed. You can measure the resistance through the thermistor wires to confirm.

 

I had a ramps board that wouldn't read the bed temperature. Turns out that one of the pins for the thermistor had a bad solder to the ramps. I reflowed it now it works great

 

Hey guys, sorry about the confusing post. It may be a bad solder, but I would think unlikly since it worked with the old bed for 5 months. I would assume that something got shorted out when the wires became exposed.

 

There's not really a whole lot to short out. Working for 5 months is not a real indicator as it could have been loose the whole time but was still making enough contact to show the temperature.
http://reprap.org/wiki/RAMPS_1.4
http://reprap.org/mediawiki/images/f/f6/RAMPS1.4schematic.png
http://reprap.org/mediawiki/images/c/ca/Arduinomega1-4connectors.png

Pull the ramps apart from the arduino and see if you notice anything on the underside.

 

Great! Thank you Mike, I will take a look tonight.

 

OK, so I took a look at the back of the RAMPS board, solder points look good, in my opinion. I have posted a picture in case you can see anything. I took resistance readings and found that the thermasistor is reading 121 ohms (id imagine that is good, room temp is about 70F) The therm1 pin set reads 7.3 ohms. Any other thoughts?

 

Ok gents. I adjust the firmware to read from therm2 instead of therm1 for the print bed and now it's working. It is printing now so all should be fine, I will replace the RAMPS board eventually, however right now the only issue I am seeing is that therm1 pin set is not working.