Treadmill DC motor control

Ok guys, here is a worthwile task I ve been repairing treadmill for years. One common repair is 2 replace a Morot controller ( known as Lower board).

Normally, this board is iether SCR or PWM speed contoller for a 95-110 volt DC motor. In many times it also feeds the elevation motor, which is a small AC motor with a gear box.

When this lower board stops working, mostly it does not feed the DV motor anymore, and sometimes the incline motor is still fed.

Companies who make Treadmills never reveal how 2 repair these board (ALTHOUGH) some of them sell refurbished boards.

Lowers boards sell between 120 - 550 $ depending on make and model.

Output stage on these boards consist of abnd SCR, MOSFET and a bridge diode. Can anyone suggest a way 2 repair such boards.?? plz advise

Thanks Samy Goldenshuttle TORONTO

Reply to
Goldenshuttle
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Just use standard electronics troubleshooting techniques. I've looked at the board in mine before and it's fairly simple. I would expect the usual problem to be blown output devices (SCR, MOSFET, etc) should be pretty easy to track down the problem with a multimeter.

Reply to
James Sweet

On 20 Feb 2006 21:58:41 -0800, "Goldenshuttle" put finger to keyboard and composed:

I've repaired boards for other equipment that uses MOSFET controlled DC motors, eg floor scrubbers and scooters. The usual fault is blown output devices. All that is required is replacement of the MOSFETs and associated components (eg zeners and diodes), and possibly the smaller transistors in the previous stage. Of course you will need to check the motors for worn brushes, etc. When choosing a suitable replacement MOSFET, pick the one that has the lowest Rdson. That will minimise its heat dissipation.

- Franc Zabkar

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Reply to
Franc Zabkar

Franc,

Quick question...

...since it's a "DC" motor, are the speed controllers just a MOSFET (or other switch) being turned on by a variable duty cycle pulse? ... with a catch diode in parallel with the motor for when the switch opens? I.e., really just a giant buck-style switch-mode power supply?

Reply to
Joel Kolstad

On Wed, 22 Feb 2006 20:11:14 -0800, "Joel Kolstad" put finger to keyboard and composed:

The devices I've encountered use H-bridges consisting of two pairs of MOSFETs. These allow for forward and reverse motion. PWM is used to vary the speed. There are single diodes or series diode pairs across the drain and source of each MOSFET (but not always, as MOSFETs have their own internal body diodes) and a suppressor across the motor. I only get to see the controller PCB, so I'm guessing the motor snubber is a transient suppressor consisting of two back-to-back zeners. At least that's how it appears in the wiring diagram.

- Franc Zabkar

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Reply to
Franc Zabkar

Generally yes, it's a standard PWM DC motor controller.

Reply to
James Sweet

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