Treadmill problem- not the motor controller this time

Thread Starter


Joined Feb 25, 2021

I have a Horizon SC220T treadmill with a display that resets frequently- it happens regardless of the belt running or not, though the whole machine shuts down when the display flicks off. Video at
The heatsink/mount has this data sticker
(1.75-2.0HP)/110v JC22-001
SJED08092HF VER:H109 S106
The board is labelled JOHNSON FITNESS JDYF02L.

I don’t believe it is to do with the LCD board as the VDD coming up to the display board will drop off from 16v to around 1.8v when this resetting occurs. The source of the VDD at the connector on the control board exhibits this as well, regardless of the cable from mainboard to display board even being connected.

The diagnostics within my capabilities so far are to find that the VDD to the display board drops off and the path to VDD is as follows: AC in (black wire) > MP3508w bridge rectifier positive (+) output > mystery component (circled in red in photo) > 25v 820uf capacitor >VDD as pins 5 and 6 of 12-pin connector to display board. The display works correctly and can start the belt so long as voltage stays up.

When I plug the machine in, the rectifier DC voltage started around 14v and crept up to 20.4v over approx. 45 seconds and stayed there. The voltage at VDD on the mainboard is always 1.8v-16v regardless of rectifier voltage.

I’ve looked the board over front and black, cleaned the dog hair off it and don’t see any bulging caps and it doesn’t smell like it has let the smoke out recently. I’d appreciate some direction or suggestions.