Prev: Repairing a Sony Tape Deck
Next: RCA TV F25216BC, ch CTC185AB3, Won't Turn On
From: jdgill on 30 Nov 2006 10:36

John:
I repaired a motor controller board for a Sears treadmil a few months
ago. I don't
think it was the same model. My board had about 5 SCRs on a heat sink
that wrapped around the board. Two of the SCRs were bad; replaced them
and that fixed the problem. Some of the SCRs were used as diodes to
convert the input AC to DC to provide the running voltages. I had to
get
the exact same SCRs for the unit to work. They were in TO-220 cases.
Hope this helps..
John G

From: John on 30 Nov 2006 10:50

Hi John G.,

I believe you are describing the MC-60 board. I can tell you that,
visually and electronically, it is a completely different animal. My
board has only one heat sink that goes down one side of the board.
Screwed to that decent radiator is a single FET and a High Powered
Diode of some sort.

Thanks for the help, but repairing an MC-70 with notes on an MC-60 will
be helpful, but it's probably not going to get me to the finish line.

The big Identifier of an MC-70 is two large black ELNA electrolytics
sitting next to a one big mother of a brick-cased rectifier, and a heat
sink that runs the length of one side of the board.

Here is a link to a page displaying the MC-60 and the MC-70 boards.
Maybe this will help others help me.

http://www.treadmilldoctorstore.com/Products-Services/Power-Boards-Electronics_5

Thanks to John G. for trying,
John

From: John on 30 Nov 2006 16:05
Dang! You're right Franc, that doesn't sound right. What the heck was I
thinking? The FET has to be fed by a smaller amplifier driver, or
directly from the output of a PWM circuit. I remember building a
variable PWM circuit with a 555 timer (1st semester freshman year in
digital design 101).

I'll get the part number for the diode. D1 has only two leads.

What the heck is the relay for? Oh ... duhh. It's for the bridge
rectifier ... that's a DC motor! So the Motor Controller Board has it's
own power supply that is completely separate from the Power Supply
Board. The Power Supply board just powers the treadmill computer and
sensors. Yeah, that makes sense. They must have done that to keep the
noise out of the computer electronic circuits.

All right. I'll go stare at the board again.

 | 
Pages: 1
Prev: Repairing a Sony Tape Deck
Next: RCA TV F25216BC, ch CTC185AB3, Won't Turn On