Bremshey Exercise bike
This is as repair of an Bremshey exercise bike.
Problem 1: The screen was not working it was not showing a picture. This clued me in that no power was getting to the display, as I examined it the main power was ok but a 3.3V LDO voltage regulator was broken, after de-soldering it and replacing it the screen came back to life.
Here is the display
You can see the sot-23 voltage regulator by the red arrow to the left.
Problem 2. The second problem was that the exercise bike difficulty level was not working.
There is a motor that moves the magnet closer to the wheel, in the picture to the left the red wire is + for the motor and the black is the -
The other wires (yellow, blue, green) are connected to a 5k ohm potentiometer this is used to determine the position of the magnet on the wheel.
I first thought that this could be the problem but they all tested ok.
Note (Red+, black-) for motor
(yellow, blue, green ) for POT
(Purple-, pink+ light green COM) - main power 9V DC
(White brown) for seat sensor
Not sure for other colors.
The next thing to test was if the red and black wires were getting to the CPU.
You can see the colors of the wires going to the CPU to the left I made a quick sketch below showing what color controls what. In my case I was testing the far left wire eg (red and black wires) because they are both connected to the motor that controls the bikes difficulty.
After testing each wire I found a broken wire on the red wire. I took the connector apart and re-soldered the wire back on .
This should solve your issue.