True 500HRC Treadmill (ME62T controller) no power to motor

Thread Starter

Giomonte

Joined Jun 26, 2020
10
2 questions: motor and controller

Controller:
Before removing motor and controller, I confirmed that display works, can enter calibration mode, lift motor works, PWM signal LED lights, and did not visually find anything broken or discolored on the board . However MTR (motor) LED does not light. Removed board, attached PWM signal generator (have done this before), and attached good motor: nothing. I'm new to electronics. Does this suggest to anyone the problem, or a short list of likely failed components?

Motor:
Removed motor from treadmill. Tried to connect it to 12V car battery, but sparked strongly at battery (shorted?). It turns by hand with more than normal resistance. Actually, 1/2 turn is normal, 1/2 is resistant. Opened motor; bearings are good (possibly replaced once---rubber seals); no visual discoloring of windings; brushes nearly new; motor clean and unscratched; did not find short between rotor at stator. Does this suggest to anyone the likely problem? Thank you.
 

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MaxHeadRoom

Joined Jul 18, 2013
21,233
Not familiar with that controller, but normally there should be no problem connecting to an automotive battery.
Did it attempt to turn? You might see a spark when you connect, but after that it should spin up OK.
The typical motor normally spins easily by hand and no resistance unless you short the leads together while spinning.
Max.
 

Thread Starter

Giomonte

Joined Jun 26, 2020
10
To be more clear, I could not connect and hold motor leads to battery; violent spark; battery sparked as when touching battery leads directly together. Motor "attempted" turn 1-2 degrees. By hand, motor turns easily for 1/2 turn, stiffly for second 1/2 turn, more stiff than with shorted leads together on the same type (working) motor. Thanks.
 

MaxHeadRoom

Joined Jul 18, 2013
21,233
Sounds very much like you have a dud motor!
It could also have damaged components on the board, if it is shorted as bad as it sounds.
Max.
 

Thread Starter

Giomonte

Joined Jun 26, 2020
10
Sounds very much like you have a dud motor!
My sentiments as well! Thanks for the tacit confirmation. It's frustrating to see everything visually normal inside and out, and basic resistance/continuity tests showing nothing apparently wrong (perhaps the resistance tests are somewhat suspect). I guess it must be something hidden in the windings. (Just curious; a hobby interest; I have access to more motors).

Any thoughts on diagnosing/fixing the controller, as per my original post? Thanks.
 

MaxHeadRoom

Joined Jul 18, 2013
21,233
The main suspects that may be damaged by a suspect motor, is the PWM device, usually the Mosfet on the heatsink, there is also a BEMF diode on the H.S. also, could be damaged, but unlikely.
Also look for any heat-damaged components.
Some you cn test using a 100w lamp in lieu of the motor.
.Max.
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Thread Starter

Giomonte

Joined Jun 26, 2020
10
The PWM circuitry appears to work; PWM LED lights (on and off treadmill), and blink rate varies when I vary the signal Hz when connected to PWM signal generator (a hookup I've done other times).

MTR LED does not come on, but with multimeter I did register ~17W across the motor terminals??

I tried to test the Mosfet; a bit inconsistent reading, but probably a fail by comparison to a separate working board. Can Mosfets be tested accurately (multimeter test) when still connected on board?

Is the BEMF diode the one on heatsink immediately left of the Mosfet? Thanks.
 

MaxHeadRoom

Joined Jul 18, 2013
21,233
Generally it is better to take them out of circuit to test.
It does look like they are mounted adjacent, which is usually the case.
Max.
 
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