New Build. Hotend Overheating. Not Printing Yet.
My build with the Hypercube Evolution continues with a replacement BIQI KFB2.0 board. I am not at the printing stage yet. This is due to my latest problem.
The kit contains a “no-name” hotend, complete with round finned heatsink and nozzle. Looks a bit like a V5 J Head Hot End.
Everything is wired up. A 24volt power supply is being used. The printer is connected to Pronterface via USB. Using Pronterface, I set the hotend temperature to 70 degrees. The KFB2.0 board lights a bright red LED when power is being sent to the hotend (and/or the heated bed). On initial heating, the red LED is on until the hotend temperature reaches around 65 degrees and then turns off. The temperature continues to climb to around 120 to 125 degrees, then starts falling. At 69/70 degrees the red LED comes on again for about two seconds, the temperature continues to climb after the red LED is off to around 86 degrees. It then cycles around the 69/70 to 86 degrees position.
I have removed the thermistor to check its resistance. Reads greater than 100K Ohm. When in situ in the hotend, it was reading around 85K Ohm, but a bit of Kapton tape sorted that. I was now reading 100K Ohm with the thermistor in place. I then used Pronterface to set the temperature again. This time with a multimeter hooked up to the hotend terminals on the board. It confirmed that the bright red LED was sending 24v and nothing when not on, so the hotend is recording a temperature increase from around 65 degrees to 125 degrees with no power. But, I now got something different when the temperature fell back to 69/70 degrees. The red LED flickered for about two seconds and the multimeter showed readings fluctuating between 0.1 and 4.2 volts. From this point the hotend kept the correct temperature, even after I had removed the multimeter.
Has anybody any idea why the temperature is going so high and what can I do to fix it?
