Help me with a treadmill power supply

[thetundrawolf]

Hi,

I am concerned with my health and have procured a treadmill that needs some help. It was stored outside and rodents made nests on the power supply board. The board is DOA with no output and no lights illuminated when power is applied (verified power is getting to the board.)

It powers a permanent magnet DC motor of the 2 HP variety that operates around 90vdc.

Hopefully the pictures work.

The power handling diodes and transistors are, S4020L (2), D4020L (3). There is an inductive transformer as well.

I would like to use this board to create a crude potentiometer variable DC power supply to run the treadmill.


Thank you.

 

[rjenkinsgb]

I'd start by testing the big white 5K6 resistor; that appears to be the power feed to the low voltage electronics.
If it's OK, does it get warm at all after power has been on for a few minutes?

It looks like the black diode just to the right of that & level with the lower end is the low voltage rec, with the glass diode above that a zener to limit the voltage.

 

[thetundrawolf]

I'd start by testing the big white 5K6 resistor; that appears to be the power feed to the low voltage electronics.
If it's OK, does it get warm at all after power has been on for a few minutes?

It looks like the black diode just to the right of that & level with the lower end is the low voltage rec, with the glass diode above that a zener to limit the voltage.

I haven't checked the resistor yet but it does get warm yes

 

[MaxHeadRoom78]

That appears to be one of the early MC-60 series that uses a SCR bridge for control, there are a couple of sources out there for schematics, also trouble shoting sheet,
I have also posted them on the All-About-Circuits site.
The 5k to 10k lin pot goes on the Red-White-Blk stake-on tabs at the end of the board.
Also