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Re: Repairing DC Motor Speed Controller

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  • Dave Mucha
    Hi Bob. get a 10k pot and solder leads on it. on the motor driver board, you will find AC power in terminals, motor out terminals and 3 wires for the speed
    Message 1 of 5 , Dec 3, 2007
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      Hi Bob.

      get a 10k pot and solder leads on it.

      on the motor driver board, you will find AC power in terminals, motor
      out terminals and 3 wires for the speed regulation. the opto feeds
      the speed regulation, but you can just use a pot instead.

      if you look at the 3 terminals for speed regulation, you should find
      one is W for wiper. The other two are not as important, one being
      ground and the other power. These would determine if the pot spun the
      motor up or down by going clockwise or ant-clockwise.

      Also, many of the motor driver boards has a circuit that requires the
      pot to be at zero speed for a few seconds before it allows the motor
      to spin. that way, it does not start at high speed.

      Dave



      --- In Electronics_101@yahoogroups.com, "Bob Gardner"
      <bob.linda.gardner@...> wrote:
      >
      > I have been a lurker here for a while and now find myself in need of
      > some help. I am attempting to repair a treadmill that stopped
      > working rather than send it to a landfill. I have found a bad SM
      > chip but not sure how to determine it's value - so here goes.
      >
      > There are three main circuit boards - the display/control board, an
      > interface board and the speed controller board. The speed controller
      > is a Minarik Model #117494 but I have been unable to find any
      > information via web searches. There is a pin labeled PWM on the
      > connector from the display board to the interface board. The trace
      > from this pin goes to pin 1 of a 4N35 opto coupler through a 270 ohm
      > resistor and pin 2 of the 4N35 goes to ground. Pins 4 and 5 of the
      > opto coupler go to pins labeled W and H respectively on the motor
      > control board (not sure what the W and H stand for). So we appear to
      > have a PWM signal opto coupled to the drive controller. The pin
      > labeled H on the drive control board goes on to the logic part of the
      > controller board but it is also connected to the DC+ bus with what
      > appears to once have been a SM resistor - at least what's left of it
      > looks like it was a resistor. The top is blown off of it and there
      > is some minor charring around it. Any suggestions as to whether this
      > was in fact a resistor and what value I might want to start at to
      > repair it.
      >
      > The DC+ bus is supplied by a full bridge rectifier from the 110V
      > main. There is also an SG3526 PWM chip and an LMT324D op amp on the
      > controller board as well as various resistors, capacitors and 2 IR640
      > MOSFETs in parallel to actually drive the motor.
      >
      > I'm afraid I'm a little beyond my current knowledge and could use
      > some help in how to proceed. By the way, the motor seems to be fine
      > and runs well driving it separate from the controller.
      >
      > Thanks,
      >
      > Bob
      >
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