A20M hotend temperature too high ... 345 deg. celsius

[alfvv12]

hello.

big problem: during printing an object suddenly the hotend increases the temperature over the printing temperature (220deg.C) up to 345 degrees celsius.

the two heater keeps always active and are permanently heating, also after stop of printing.

i'm afraided a burning printer...

after stop of printing and restarting the printer the hotend temperature are increasing althought without starting the print.
initialize eeprom and restore settings not succussfully.

is this issue known?
is the board defect?

or other suggestions about this behavior?

greetings

[alfvv12]

hi.
problem caused myself.
i used a screw who are too long to fix the housing of the hotend.
so the screw hits the hotend board and produces a short circuit with permanent heating the heater...

stupid i was... sy.