thermistor calibration  

Re: thermistor calibration

there is no such thing like a thermistor calibration.

if your thermistor was broken, you need to replace it with exactly the same model that came with your i3 MK2(s). that's usually a ATC Semitec 104GT-2 100k Ohm thermistor.
when you've got another thermistor as a replacement, you'll need to compile the firmware for the type of thermistor you've got.
you'll find the setting (and examples) inside the Configuration_prusa.h file (which is a copy of the file from the variants folder that fit's for your printer) around line#359.
most of the E3D v6 hotend clones use the Hisens 3950 thermistor (too 100k Ohm, but with a different graph), so you'll need to compile it with #else
#define TEMP_SENSOR_0 13
#endif
but there are PT100 thermistors for the E3D v6 hotend available too.

so the first thing you have to do is to figure out what kind of thermistor you've got delivered as a replacement.

Re: thermistor calibration

OK, thanx,;
I replaced the thermistor with a Semitec 104GT (is this different from Semitec 104GT-2?), the suplier (123-3D.nl) said Marlin Settings should be #TEMP_SENSOR_N 5
Does that make sense?
B.

Re: thermistor calibration

OK, thanx,;
I replaced the thermistor with a Semitec 104GT (is this different from Semitec 104GT-2?), the suplier (123-3D.nl) said Marlin Settings should be #TEMP_SENSOR_N 5
Does that make sense?
B.

that's the value with which the genuine prusa firmware is compiled for the i3 mk2(s) and shouldn't be the problem.

so if your hotend get's to hot for what the thermistor reads, your thermistor probably has a bad thermal contact how it is assembled.
hope you didn't use thermal compound or such heat-conductive paste for CPU's as you've mounted the thermistor at the hotend. this stuff usually only works up to abot 120 - 150°C before loosing it's properties.... and afterward's it may become a good insulator.

Re: thermistor calibration

My old thermistor that got damaged during a botched PETG jam repair was heavily oxidized so put thermal paste on its replacement. I tried to use whatever E3D or Prusa used on the brake and nozzle because it must be rated for max performance range of MK2/S. But E3D sold little sachets that had no labeling or spec sheets so I sourced my own. Halnziye HY880 high performance thermal paste was what I ended up going with. It is rated for long term service of -30°C to 280°C. E3D support told me that the grease is mostly to fill air gaps and as long as the paste doesn't degrade into an insulator such as most metal oxide pastes, you should be fine. HY880 is 45% "metal oxide" which is higher than most I've found at a reasonable price. I must report though that there is a distinct smell and wisps of white smoke the first time I ran a PETG print (250°C) but all prints after were fine with no noticeable change in thermal behavior.