With the weather cooling off, dark in the morning, and soon dark in the evening, it was time to brush off the treadmill for wintertime basement running. Stepping onto the belt and turning it on, I was greeted with a low hum that sounded like the motor was trying to lower the platform. Problem was, the platform was already at the lowest point. Pushing the ‘up’ rocker switch produced nothing.
The schematics clearly showed the up/down motor controlled by the ‘lift board’, so I started tracing wires to locate the board. The location of the board again confirmed the nth corollary to Murphy’s Law, in that the probability of a component failing is inversely proportional to its accessibility.
Fortunately, it clearly said ‘Lift Board’. (If it had said Heisenberg compensator I’d have to go back and start pulling other boards.)
After testing the board with my volt-ohm meter, I found one of the triacs (one of the two black boxes with three legs in the top picture) had failed. After getting another one in through Amazon (and a two week wait), I was able to desolder the old one, and solder in the new unit.