I would like to thank those involved with this thread https://forum.allaboutcircuits.com/...ol-board-johnson-fitness-jdyf02l-revg.110355/ for all the good information about this control board. By using a combination of info, test procedures and some troubleshooting logic I was able to make a successful repair. I dabble in electronics here and there and haven't even used an oscilloscope since college. It was satisfying to troubleshoot, test and learn/re-learn along the way. Here is a list of where I started in the troubleshooting process. I've also made a very rough and partial circuit diagram with information from the board and datasheets. I hope this can help someone also looking to fix their treadmill.
As usually, the treadmill "isn't working". It powers up and displays everything as normal, however when the start button is pressed (and a few beeps are heard to tell the user the belt is about to move) the motor does not start...most of the time. Sometimes there was movement but mostly nothing. Let's do all the preliminaries like check fuses, loose connections and other anomalies that may keep the motor from starting. All looks normal. I also put a meter on the output to the motor while attempting to start...nothing. All I can here is the relay turn on and after a brief timeout period, turns off. This was an indication to me that certain criteria is being met but a malfunction is preventing the motor from starting. I did also see the red LED turn on letting me know the motor rail has power. Thanks to the discussions from the above thread, the picture of how this board operates and the common failures becomes more apparent.
Time to test stuff! I powered down everything and let the capacitors discharge before removing the board. Since the mosfet Q4 and diode D4 were common failures I removed them both and tested on a breadboard. They both tested without a problem. Now I need to dive deeper into the circuitry of this board and HOW it actually works. For that I need a diagram. Since I could not locate a schematic online I decided to draw my own. I tried to be thorough with connections, component descriptions, part numbers, etc. Using my trusty multimeter and the continuity function, I was able to come up with a partial diagram involving most of the components related to turning on the motor (power and signal). Armed with this homemade piece of information it's time to put the board back in and do more testing.
As I mentioned before, I haven't used an oscilloscope since my electronics courses in college some 20'ish years ago. This is a problem. Enter google and the owner's manual. After some tinkering I followed the PWM signal all the way back to U2 pin 8. This is the spot where I could actually see a waveform on the oscilloscope when I hit the ON button for the board. So somewhere between pin 8 and the PWM test spot the signal is not making it's way through. I then looked at the optocoupler U4 as a possible failure source. I would occasionally get a signal every time I tested the "led" pin of the optocoupler. The only component between my two testing points is a resistor labeled R48 (220 ohm). All my problems can't be caused by a resistor?? I tested for continuity directly at the solder joints connecting R48 to the board. Seemed very erratic to say the least. Also tested resistance and found 350'ish ohms?? I decided to replace it.
Plugged everything back in and to my enjoyment the treadmill started to work again! It's now been over a week with daily use and no issues. Thanks again to those involved.
As usually, the treadmill "isn't working". It powers up and displays everything as normal, however when the start button is pressed (and a few beeps are heard to tell the user the belt is about to move) the motor does not start...most of the time. Sometimes there was movement but mostly nothing. Let's do all the preliminaries like check fuses, loose connections and other anomalies that may keep the motor from starting. All looks normal. I also put a meter on the output to the motor while attempting to start...nothing. All I can here is the relay turn on and after a brief timeout period, turns off. This was an indication to me that certain criteria is being met but a malfunction is preventing the motor from starting. I did also see the red LED turn on letting me know the motor rail has power. Thanks to the discussions from the above thread, the picture of how this board operates and the common failures becomes more apparent.
Time to test stuff! I powered down everything and let the capacitors discharge before removing the board. Since the mosfet Q4 and diode D4 were common failures I removed them both and tested on a breadboard. They both tested without a problem. Now I need to dive deeper into the circuitry of this board and HOW it actually works. For that I need a diagram. Since I could not locate a schematic online I decided to draw my own. I tried to be thorough with connections, component descriptions, part numbers, etc. Using my trusty multimeter and the continuity function, I was able to come up with a partial diagram involving most of the components related to turning on the motor (power and signal). Armed with this homemade piece of information it's time to put the board back in and do more testing.
As I mentioned before, I haven't used an oscilloscope since my electronics courses in college some 20'ish years ago. This is a problem. Enter google and the owner's manual. After some tinkering I followed the PWM signal all the way back to U2 pin 8. This is the spot where I could actually see a waveform on the oscilloscope when I hit the ON button for the board. So somewhere between pin 8 and the PWM test spot the signal is not making it's way through. I then looked at the optocoupler U4 as a possible failure source. I would occasionally get a signal every time I tested the "led" pin of the optocoupler. The only component between my two testing points is a resistor labeled R48 (220 ohm). All my problems can't be caused by a resistor?? I tested for continuity directly at the solder joints connecting R48 to the board. Seemed very erratic to say the least. Also tested resistance and found 350'ish ohms?? I decided to replace it.
Plugged everything back in and to my enjoyment the treadmill started to work again! It's now been over a week with daily use and no issues. Thanks again to those involved.
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