Hi,
I'm looking for guidance on diagnosing a problem with a treadmill control board. Any help whatsoever is sincerely appreciated
My electronics knowledge is quite limited, so I've run up against dead ends.
The symptoms: The unit turns on. Pressing the start button on the console causes the motor to start to spin up, but within two seconds, the motor cuts out and a generic "Err" message is displayed on the console.
When I initially opened the unit, it was filled with dog hair, suggesting overheating.
I found this forum because I initially thought two caps on the board had gone bad. You can see the bulged tops in the first photo. The pcb is cooked underneath them, but turning the board over reveals that the burn marks are beneath the zener diode and (maybe?) the 75Ω resistor.
The two caps had around 70% of rated capacitance, and had really high esr (as determined by cheap ebay tester). The diode appears functional, with a reverse voltage drop of ~12.3v. The resistor is spot-on 75Ω (I replaced it anyways).
Replacing the capacitors did not fix the issue.
1)what am I overlooking? discrete components on the same circuit test fine.
2)I replaced the zener since it got so hot. Is it possible that the zener had shifted in value permanently, and the reverse voltage I measured is not proper for the circuit?
3)why are so many methods of voltage reference used? There are zener diodes, voltage reference ic's, and multiple low voltage ac inputs from the transformer (~12v and two separate 16v).
4)Are both chips on the secondary board opamps? (see note 3)
5)Could the PIC have failed from overvoltage? How would I test it?
Note:
1) the failed caps were Aishi brand, everything else was ChengX (and tested fine). This board has been repaired once by the seller (now defunct), so they may have been replaced.
2)the traces around the burnt spots were lifted from the heat. They may look terrible, but there are no breaks
3)The browned glue on the secondary board pins has turned conductive. (I believe it was ~100kΩ per quarter inch). Anyone smarter than me have an opinion on this (I painstakingly scraped off all of the glue
I'm looking for guidance on diagnosing a problem with a treadmill control board. Any help whatsoever is sincerely appreciated
My electronics knowledge is quite limited, so I've run up against dead ends.
The symptoms: The unit turns on. Pressing the start button on the console causes the motor to start to spin up, but within two seconds, the motor cuts out and a generic "Err" message is displayed on the console.
When I initially opened the unit, it was filled with dog hair, suggesting overheating.
I found this forum because I initially thought two caps on the board had gone bad. You can see the bulged tops in the first photo. The pcb is cooked underneath them, but turning the board over reveals that the burn marks are beneath the zener diode and (maybe?) the 75Ω resistor.
The two caps had around 70% of rated capacitance, and had really high esr (as determined by cheap ebay tester). The diode appears functional, with a reverse voltage drop of ~12.3v. The resistor is spot-on 75Ω (I replaced it anyways).
Replacing the capacitors did not fix the issue.
1)what am I overlooking? discrete components on the same circuit test fine.
2)I replaced the zener since it got so hot. Is it possible that the zener had shifted in value permanently, and the reverse voltage I measured is not proper for the circuit?
3)why are so many methods of voltage reference used? There are zener diodes, voltage reference ic's, and multiple low voltage ac inputs from the transformer (~12v and two separate 16v).
4)Are both chips on the secondary board opamps? (see note 3)
5)Could the PIC have failed from overvoltage? How would I test it?
Note:
1) the failed caps were Aishi brand, everything else was ChengX (and tested fine). This board has been repaired once by the seller (now defunct), so they may have been replaced.
2)the traces around the burnt spots were lifted from the heat. They may look terrible, but there are no breaks
3)The browned glue on the secondary board pins has turned conductive. (I believe it was ~100kΩ per quarter inch). Anyone smarter than me have an opinion on this (I painstakingly scraped off all of the glue
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