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Marantz 5220 motor

Discussion in 'Tape' started by lazol, May 15, 2018.

  1. lazol

    lazol New Member

    Messages:
    31
    Hi everyone, i got a nice 5220 as a trade, in non working condition. No play, ff, rew, nothing.
    The motor was dead.
    I fast realized that the problem is in that little board in the attached pic. Does anyone know what's the function of it? The power, before entering the actual motor, pass through this simple circuit. If i bypass the circuit, the motor works and the deck sounds great.
    Unfortunately that board is not explained in the service manual: it's considered part of the motor.
    Thanks for any info!!
    20180515_131949.jpg
     

     

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  2. dhnash

    dhnash Well-Known Member

    Messages:
    509
    Location:
    Wildwood, MO
    HiFi Engine has a service manual for this unit which you can download for free after registering (also free):

    https://www.hifiengine.com/hfe_downloads/index.php?marantz/marantz_5220_service.pdf

    On page 16 of the manual, there is a procedure for adjusting the capstan motor speed that shows a small circuit board connected to the motor. This is probably a servo-control circuit for the motor. The motor has an internal frequency generator that provides a feedback signal to the servo-control circuit which in turn regulates the speed of the motor.
     
  3. lazol

    lazol New Member

    Messages:
    31
    Thanks for your answer.
    I doesn't look that the one at page 16 is the circuit board of my picture though, there's no variable resistor to adjust in it.
    There are only 3 elements there: the positive pass through what i thought it's diode, but it's not, it's like a little cilinder with copper wire around. The negative pass through another component that i believe it's the same thing (not sure though, because it's wrapped). Then there's a capacitor between the pos and neg, that's it.
    I could try to replace the capacitor, the only known component of the 3...
     
  4. dhnash

    dhnash Well-Known Member

    Messages:
    509
    Location:
    Wildwood, MO
    The “little cilinder with copper wire around” is an inductor which is used in combination with the capacitor to help keep noise generated by the motor commutator from being introduced to other circuits. The “wrapped” component may also be an inductor. If you have a DMM, you could check for continuity through each of these two components to make sure that neither of them is open circuited.
     
  5. lazol

    lazol New Member

    Messages:
    31
    Are you insinuating i don't have a degree in electronic??:D:D
    Anyway, i figured out that it must have been a filter of some kind. Very skeptical about the capacitor failure, i went ahead with a voltometer checking where the tension was dropping and i finally solved the case: the red connection wire going to the "filter" was cut off. Easy fix, but not immediate to find out, because the cut was right underneath a bundle of wires.
    Soldered back and all is good:))
    Thanks for your help and time!
     

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