Treadmill problem - inconsistent speed

[peterlonz]

I have Weslo treadmill which will not hold to a set speed, the actual speed varies, generally falling & then recovering making this piece of equipment useless as is.
It is made up of a brushed universal motor, belt driving to the walking belt. The walking belt roller pulley has a magnetic pick up for the speed digital display. Speed is set by a sliding rheostat. Speed control is via a circuit board, the exact design of which I am uncertain, but it's probably some sort of pulse modulation & fairly well known technology to speed control experts.
I have checked the motor brushes & the sliding potentiometer, both seem fine. Is there any way to establish whether the speed control board is "probably faulty". Replacing either motor of speed control board would be uneconomic, the treadmill is a "low cost" unit. But if a suspect component could be located on the speed board, that could easily be replaced.
Any ideas?
Thanks
Pete

 

[ColJack]

might be the magnetic pick up?
does it feed back to the speed control?

 

[peterlonz]

No the magnetic pick-up seems OK.
It appears to accurately report the walking belt speed as it moves from the desired setting.
I do not believe there is any feedback to the speed control circuit board from this speed sensing device.