Hi everyone. I am having a problem with this MC-02 treadmill motor control board. In the treadmill it is not working. there is no power going to the motor terminals. Taking it out and testing it on the bench the motor starts up full speed with no control from the potentiometer?? I have tried searching in this thread with no results. Maybe someone here have seen this before and can help.

 

No familiar with that version, but sounds like the control device that is connected to the motor may be the problem
What are the part No's on Q3 Q4 ?

 

No familiar with that version, but sounds like the control device that is connected to the motor may be the problem
What are the part No's on Q3 Q4 ?

Thanks MaxHeadRoom the part # for both Q3 & Q4 is S4008R.

 

S4008 N-channel MOSFET

https://fscdn.rohm.com/en/products/databook/datasheet/discrete/sic/mosfet/s4008-e.pdf

 

I would remove and test them for short circuit.

 

S4008 N-channel MOSFET

https://fscdn.rohm.com/en/products/databook/datasheet/discrete/sic/mosfet/s4008-e.pdf

I would remove and test them for short circuit.

Thanks for the data sheet MrChips and thanks MaxHeadRoom will give it a try

 

Thanks for the data sheet MrChips and thanks MaxHeadRoom will give it a try

If they are shorting that will show up without having to remove them from the board.

 

If they are shorting that will show up without having to remove them from the board.

Thanks MrChips. That would save a whole lot of work. For those with limited knowledge of testing these mosfets in circuit or out maybe you would explain how to know a mosfet is shorted by testing it in circuit. What to look for, on what setting?

 

The photograph of the MC-02 controller you posted on post #1 is of excellent magnification and quality. Can you do the same for the bottom side?

 

S4008 can also be an SCR (silicon vontrolled rectifier) made by Teccor Electronics now owned by Littlefuse.



If it is an N-channel MOSFET, here is the pinout.



In either case, measure the resistance between pins 2 and 3, drain and source, or anode and cathode if it is an SCR.

With the DMM set to diode or continuity range, the meter should "beep" and show .000 if there is a short circuit.
Also set the DMM to measure resistance. If the resistance is less than 100Ω it is possibly a short. A meter reading of 0L means that the resistance is over the range of the meter setting. Try a higher resistance range.
Do all the measurements with the board disconnected from power and the motor.
Do the measurements without removing the components from the board.

 

S4008 can also be an SCR (silicon vontrolled rectifier) but I doubt it.

View attachment 360478

Thanks MrChips I do believe Q4 is shorted. All pins has a path to groung. In replacing Q4 would it be adviseable to replace Q3 as well? Can I replace it with something other than S4008R? If so what should I look for in the spects

 

The photograph of the MC-02 controller you posted on post #1 is of excellent magnification and quality. Can you do the same for the bottom side?

Will do when I pull Q4

 

Will do when I pull Q4

Can you take the photo before pulling Q4?
We still need to identify if the device is a MOSFET or SCR. Hopefully, reverse engineering the board will tell us.
We want to see the PCB tracks on the board. The contrast between the tracks and the board will depend on the angle of the lighting.

If you are going to pull Q4, it is easier to clip the legs on the top side and then unsolder one pin at a time.

 

Will do when I pull Q4

Here you go my friend the back side of the MC-02

 

Can you take the photo before pulling Q4?
We still need to identify if the device is a MOSFET or SCR. Hopefully, reverse engineering the board will tell us.
We want to see the PCB tracks on the board. The contrast between the tracks and the board will depend on the angle of the lighting.

If you are going to pull Q4, it is easier to clip the legs on the top side and then unsolder one pin at a time.

Thanks for the tip on de-soldering. Photo sent as requested Let me know if lighting is ok?

 

Thanks for the tip on de-soldering. Photo sent as requested Let me know if lighting is ok?

Thanks for the photo. The contrast is poor. Can you try with brighter light at a different angle?

 

Try these

 

That’s much better. Thanks. I will look them over.

 

If that is two SCR's then it is using the same method as the MC-60 board where the SCR's are part of a full wave bridge, there are two large diodes that complete the briodge.
D9 - D10 ?

 

I am going to go with Max's suggestion that it is a Littlefuse S4008R SCR. (The R option means that it is non-isolated, i.e. the tab is connected to pin-2.)

https://www.littelfuse.com/assetdocs/discrete-thyristors-sxx08xsxsxx08x-series-datasheet