I'm having this same issue I recorded it...
YouTube
I've tried different heater resistors and thermistors and different power supplies.
This email from POLYPRINTER helped, but alas I'm not printing yet(my reply is in
bold)
But failure to reach temperature can come from several things:
Too much resistance.
8 Ohms
Not getting full PWM on-time.
How do I check this? I have an O-scope
Too low a voltage.
The voltage is easiest. Measure the power supply voltage while the heater is on, and see if it's what it is supposed to be.
11.57 Volts across pos/neg terminals to the Board PS input when it's up to 145 deg. Before heat is turned on voltage is 11.82 PS input
Then also measure it when the head first begins to heat up
11.59 volts across pos/neg terminal input to the board , or is cold - you can disconnect the head heater and measure the voltage to the heater when it's disconnected
Heater disconnected heat turned on 11.82 across PS input 11.77V across heater terminal- , and even better, when it is connected and beginning to heat up
Heater turned on leads across heater terminal 11.5. If it's not nearly the power supply voltage, the PWM isn't getting to 100% or there is resistance somewhere else in the circuit (but if so, it's going to be getting hot wherever the problem is).
You can also, with the head heater disonnected fromthe circuit, measure its resistance - it shold probably be about 6-10 Ohms
8Ohms if it's a 12v heater, or 25 to 40 Ohms if your printer uses a 24v supply. But you can ask on the user forums what it should be, I suppose.
Let me know what you find, if anything.
I do have a second power supply and it reaches 12.2 v across the input terminals and 12.03 when the heater is on. Also 12.03 across the heater terminals when it's on.
PolyPrinter