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

Goldenshuttle wrote:
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



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.

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

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

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
--
Please remove one 'i' from my address when replying by email.

Franc,

Quick question...

"Franc Zabkar" wrote in message
...
DC motors, eg floor scrubbers and scooters. The usual fault is blown
output devices.

....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?

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

Franc,

Quick question...

"Franc Zabkar" wrote in message
.. .
DC motors, eg floor scrubbers and scooters. The usual fault is blown
output devices.

...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?

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
--
Please remove one 'i' from my address when replying by email.

Joel Kolstad wrote:
Franc,

Quick question...

"Franc Zabkar" wrote in message
...

DC motors, eg floor scrubbers and scooters. The usual fault is blown
output devices.


...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?




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