MC2100 Rev B - Treadmill Runs for a couple second then stops

Thread Starter

eewill

Joined Jul 27, 2020
18
I have a MC2100 Rev B V#37376 controller board still in a Nordictrack C2000 Treadmill. The treadmill powers up and motor spins for about 2 second before shutting down. All lights on upper panel go out and come back on after shut down. Pressing the STOP button and the START again will cause the same thing to happen.

Looking at the motor control board, the reed switch is functioning correctly. The red led comes on and stays on solid. The 5V regulator checks out. I had to create my own schematic, so if one exists for this board, that would be awesome! I attempted to short the terminals of the motor temp sensor on the board to rule out a problem there, but got sparks somewhere in the area of the micro and I decided not to try that again. The unit still behaves the same after that and I couldn't find any residue of where the sparks originated. Should I be able to short those terminals without a problem?

I'm looking for some ideas of what to look at next. I have a multimeter and I can mostly just see voltages come up and then go right back down.

Thanks!
 

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MaxHeadRoom

Joined Jul 18, 2013
21,644
Search previous MC2100 threads for reverse-engineered schematic, it does not cover all versions, but close.
What does the diagnostic LED show?
Max.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
Max,

I assume that's the lonely LED on the board? It comes on and stays solid. I can't tell that it flickers when the motor briefly runs.

Should I be able to short out the motor temp sensor terminals on the board without any ill effects? Like I said... I was getting sparks elsewhere on the board.
 

MaxHeadRoom

Joined Jul 18, 2013
21,644
What is the header label for the motor temp plug in, many vary, and some do not have it.
Are you refering to the NTC Current/temp sensor mounted on the board?
Max.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
I'm talking about the two big blue wires at the top of the image I posted. They run through the reset switch and then to a temp sensor on the motor (I think that's what it is) and back to the board. They are labled as CB1 and CB1A.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
Essentially, the treadmill powers up. When you hit the START button, the belt spins for about 2 second before it stops. Pressing the STOP button and then the START again repeats the 2 second run. I'm trying to debug and find what is causing it to stop.
 

MaxHeadRoom

Joined Jul 18, 2013
21,644
Does it start in high speed, or start to ramp up as it should?
I have 3 versions here, one of them a REV B. There is no temp sensor, just the CB1A/B for O/L switch.
And a MOV1 next to it, that is across the supply, so don't short that out.
Max.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
Does it start in high speed, or start to ramp up as it should?
I have 3 versions here, one of them a REV B. There is no temp sensor, just the CB1A/B for O/L switch.
And a MOV1 next to it, that is across the supply, so don't short that out.
Max.
What is the O/L switch? That is in the motor? So, don't short that out, correct?

It's hard to say that it's ramping since it only has 2 second to do anything. Mostly it starts at a slower speed like it's just coming up. On occasion, it seems like it's starting to spin a lot faster.

I have tested the reed switch that senses the magnet on the motor wheel. It's working fine.

I was trying to proceed under the assumption that something is turning the motor back off. Maybe a safety feature that isn't functioning properly anymore, but not sure where to look. You only get 2 second of debug time before it shuts down.
 

MaxHeadRoom

Joined Jul 18, 2013
21,644
The O/L (Overload) switch connects to CB1A/B , this is a thermal ON/OFF Toggle/Trip switch.
It sounds to me as though either the motor MOV is defective or the belt RPM sensor is not registering, the sensor usually comes in to the board but goes directly to the console through the HD2 connector.
Where it is sensed,and the correct command is sent down to the motor board through the same HD2.
Max.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
The O/L (Overload) switch connects to CB1A/B , this is a thermal ON/OFF Toggle/Trip switch.
It sounds to me as though either the motor MOV is defective or the belt RPM sensor is not registering, the sensor usually comes in to the board but goes directly to the console through the HD2 connector.
Where it is sensed,and the correct command is sent down to the motor board through the same HD2.
Max.

Max,

Sounds like there shouldn't be a problem shorting out CB1A/B if it's just the reset switch and the OL switch in the loop.

The belt RPM sensor (this is the magnetic reed switch, correct?), It's working fine. I tested it with continuity check and spinning the belt wheel manually.

Can you recommend some tests I can do to check for the problem?
 

MaxHeadRoom

Joined Jul 18, 2013
21,644
What is handy for testing these boards stand alone from the console is a PWM board that plugs into the HD2.
You can test the motor circuit this way.
In the absence of this, I would do some continuity checks on the Mosfet and maybe the other motor devices on the heat sink, it is a little easier to remove the board from the Aluminum frame in order to do this.
You can also run it very briefly this way when testing, ensure the heatsink insulation is present when refitting the board.
I made up some circuit board for running these T.M. as a stand alone, also many use them when running ina non T.M. useage.
Max
 

Thread Starter

eewill

Joined Jul 27, 2020
18
What is handy for testing these boards stand alone from the console is a PWM board that plugs into the HD2.
You can test the motor circuit this way.
In the absence of this, I would do some continuity checks on the Mosfet and maybe the other motor devices on the heat sink, it is a little easier to remove the board from the Aluminum frame in order to do this.
You can also run it very briefly this way when testing, ensure the heatsink insulation is present when refitting the board.
I made up some circuit board for running these T.M. as a stand alone, also many use them when running ina non T.M. useage.
Max

Sounds good. I'll try that. There is no go way to check that PWM on HD2 with only a multimeter is there? Hopefully this is only a one-time debug and I won't need a continued need for a PWM test board.
 

djsfantasi

Joined Apr 11, 2010
6,982
Max,

Sounds like there shouldn't be a problem shorting out CB1A/B if it's just the reset switch and the OL switch in the loop.

The belt RPM sensor (this is the magnetic reed switch, correct?), It's working fine. I tested it with continuity check and spinning the belt wheel manually.

Can you recommend some tests I can do to check for the problem?
From the TS description, I think he’s attempting to short out the MOV. Since its terminals are across the supply, he’s shorting the supply. Basically, don’t do that.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
From the TS description, I think he’s attempting to short out the MOV. Since its terminals are across the supply, he’s shorting the supply. Basically, don’t do that.
I'm not saying this isn't what is happening... I followed the circuit path before I did.

Following those two blue wires at the top of the picture I submitted - here is what it goes through (in series):

1. AC HOT attached to CB1 on the board
2. blue wire leaves CB1
3. blue wire enters Reset/Off switch on treadmill casing
4. blue wire leaves Reset/Off switch
5. blue wire enters motor
6. blue wire leaves motor
7. blue wire returns to CB1A
8. CB1A connects on the board to one of the AC terminals on the bridge

My idea was that shorting these two terminals (CB1/A) only removes the two switches from the circuit. That would allow me to rule out any issue there.

Just trying to find a logical way to figure out what is going on here.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
Okay. Worked on it a little more this evening.

Pressing START or a SPEED NUMBER on the console causes the motor to run for only a couple of seconds before it stops. The ENTIRE machine cycles power (most of the time... occasionally the console on top stays powered up).

The red LED stays on solid with no flashing (except during power cycles).

If I disconnect the two motor wires from the control board, I no longer get the power cycling. Voltage across these two connections runs up to just over 100V and then starts to degrade. Probably a capacitor charges up and then the motor driver shuts off.

I have a small 2A 12V DC power supply. I used this to test the motor. The motor spins slowly and turns for about 5 seconds before it kicks the breaker on the supply. Repeated testing eventually kicked the GFI house breaker. (Garage outlets are on the GFI circuit)

Tested voltages on the blue wire from HD2 at various speeds (motor has already stopped running) and saw it change. It only ranges from about 0.15V to 0.95V though.

Visually inspected all components and don't really see anything wrong with them. C2 has some doming on top, but it seems to test ok.
 

MaxHeadRoom

Joined Jul 18, 2013
21,644
The normal operation of the LED is to be ON, until a command is issued, then it is a steady regular flash.
Use an automotive battery to test the motor, also check continuity from power to the motor frame, it should be infinity or close.
HD2 pin 4 is the 20Hz PWM command signal.
C2 typically is sized very close, in some versions, under rated.voltage wise.
Max.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
Gotcha.

So. Trying to follow the operational logic of the system and what I know:

1. System powers up. Lights on console work, red LED on motor control board lights solid. At this point the motor is OFF.

2. Pressing START or a SPEED NUMBER on console causes a signal to be sent on HD2 pin 4 to the control board

3. The micro receives this signal on pin2

4. (Magic happens here inside the micro)

5. The micro then puts out a fix period signal on pin 8

6. This signal goes to U9 (MIC4227) and drives the MOSFET Q2

7. Turning on Q2 with a 60 usec fixed period, variable duty cycle signal turns the motor on and varies the speed.

Correct?

I'm not sure what drives the red LED. Is it the micro directly? At some point this should start flashing to say it's receiving signal.

In my case, the red LED does not flash, which should indicate that a command was not received.
Even though the motor turns off after 2 second, doesn't the fact that it turned on to begin with mean that a command was received?


Another test case: Shorting out the thermal switch on the motor (connects to pins CB1 and CB1A) causes the motor to spin up fast before the system turns it off. ( To see what I'm actually shorting out, refer to the attached wiring diagram. This is how my system is wired with CB1 and CB1A connected to the breaker switch and the motor thermal switch)

This seems to indicate that the system is not getting feedback from the TACH. I know the reed switch on the TACH is working, where does this signal go?


My working theory now is that I have to issues:
1. Possibly a bad Thermal Switch on the motor (or the motor really is overheating)
2. Something is off with the TACH signal.

Thoughts?
 

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MaxHeadRoom

Joined Jul 18, 2013
21,644
That is correct, the LED normally flashes steady if the received signal on P4 is OK and the belt speed registers correct.
The thermal motor switch should normally be zero resistance, anything else points to a failure.
You can short it out for a test as many T.M.'s just have the Red thermal breaker/switch
Max. ,
 
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