Horizon incline motor does not stop
I bought a used Horizon CT7.1 (about 4 years old) turned it on and it was working for about 3 minutes.
Then I changes some settings (speed , incline) and the running belt stopped and the incline moved to the highest level.
It seems that the incline motor doesn't even stop (and tries to incline even more) as the incline motor gets hot.
Even when I unplug/turn off the treadmill and then turn it on again, the incline motor immediately tries to incline even more (but its already at the maximum).
The display still indicates speed and incline level according to my button settings - but as already mentioned, the belt is not moving and incline is on max.
I contacted already Horizon and they say that most likely the upper control board is broken.
(but a new upper control board would cost even more than I paid for the treadmill)
As I have an electronics engineering education I would be able to check, repair something on the board.
Do you have a hint for me, what could be broken or what I could check/replace or a circuit plan?