So, the thermistor is connected to pin J206-5 and from there directly to pin 34 of the IC A. There's a just a "332" (tested OK) resistor in between.
When I start the printer, the voltage at pin 34 briefly jumps to about 4.5 V and then it's game over.
According to the documentation, error conditions 1), 2) and 4) are time sensitive, so to speak, as they are checked after some time the printer is up and running. Condition nr 3) (temperature above 230 deg C) is the only one which seems to be constantly checked.
So, one possibility is that 4.5V as indeed too low (??? voltage drops as temperature raises) and it's triggering the safe mode. But 4.5V seems quite a high level...
I think we are looking at the wrong part of the printer, but honestly I no longer have ideas about where else to look at...
When I start the printer, the voltage at pin 34 briefly jumps to about 4.5 V and then it's game over.
According to the documentation, error conditions 1), 2) and 4) are time sensitive, so to speak, as they are checked after some time the printer is up and running. Condition nr 3) (temperature above 230 deg C) is the only one which seems to be constantly checked.
So, one possibility is that 4.5V as indeed too low (??? voltage drops as temperature raises) and it's triggering the safe mode. But 4.5V seems quite a high level...
I think we are looking at the wrong part of the printer, but honestly I no longer have ideas about where else to look at...