Faulty treadmill controller - Endex DCMD57

[Kevin H]

My son was using our Tunturi treadmill last night - he ran on it for an hour at 10 khm, which is the most work it has ever done. Afterwards he noticed a burning smell. I pulled the controller board from it today and the source of the smell is obvious - a (rather small) resistor is black and charred. See image.

The board model number is DCMD57 and it's made by Endex Auto Tech.  Unfortunately the resistor is unidentifiable due to the burning so I have been looking at photos of the same board on-line and this resistor doesn't appear on other boards which otherwise appear to be identical. I haven't been able to find a wiring diagram for this board and it appears to be a multilayer board so working out the circuit is going to be difficult. Companies who sell a replacement board offer a later version which is quite different.

Does anyone have any suggestions as to how I approach repairing my board?

[Kevin H]

I found a picture of the exact same board  - see attached. It appears to have suffered the same way and has been repaired, but the new component doesn't look like a resistor. Any ideas what it could be?

[xavier60]

The replacement part looks like a fuse. The original might have been a fusible resistor.
There are more complications there compared to usual switch mode power supplies.
Is the motor control done on the live side?

[Kevin H]

Thanks for your response xavier60 and apologies for the delay in responding.

I'm sure it didn't help that the component was covered with glue.

Is the motor control done on the live side?

Not sure what you mean by that?

The motor as a 180v DC drive.

As the treadmill was apparently still working when it was turned off, I decided to put the board back in and try it again. The damaged component starts smoking immediately the machine is turned on.

[xavier60]

It looks like the motor connects on the live side of the power supply, not the isolated side?

[xavier60]

Also check to see if the overheating part is in the motor current path.

[Kevin H]

It looks like the motor connects on the live side of the power supply, not the isolated side?

I don't think it does, but I will check.

Also check to see if the overheating part is in the motor current path.

Again, I don't think that is the case. One side of the component is connected to the incoming AC neutral line.

I have removed it now (see photo attached ) and it has a resistance of 35 ohms.

Either later today or over the weekend I will dismount the circuit board and trace out the circuit so we have a better idea of what we are dealing with.