Yamaha CR640 tuning meters

Discussion in 'Tuners' started by Soundslave, May 6, 2017.

  1. Soundslave

    Soundslave AK Subscriber Subscriber

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    i have a Yamaha receiver that tunes stations OK but the meters do not respond. Any ideas on what I could do to change this?
     
  2. avionic

    avionic " Black Knights " Subscriber

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    No movement at all ?
     
  3. Soundslave

    Soundslave AK Subscriber Subscriber

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    The signal strength meter deflects when tuning the dial then falls to zero on station. The centering meter moves some but always stays to the left of center.
     
  4. avionic

    avionic " Black Knights " Subscriber

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    Does the tuner work ok.
     
  5. avionic

    avionic " Black Knights " Subscriber

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    Are you using and antenna of some sort ?
     
  6. Soundslave

    Soundslave AK Subscriber Subscriber

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    The tuner works ok and yes I'm using a T type like what come with them from the factory.
     
  7. avionic

    avionic " Black Knights " Subscriber

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    Are you getting "stereo" indication with the LED's. Do the LED's appear to be functioning correctly ?
     
  8. Soundslave

    Soundslave AK Subscriber Subscriber

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    Yes, stereo light comes on when you get it on the station
     
  9. avionic

    avionic " Black Knights " Subscriber

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    Location:
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    With power off does the tuning meter point to zero ?
     
  10. Soundslave

    Soundslave AK Subscriber Subscriber

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    With no power the tuning meter goes to center.
     
  11. avionic

    avionic " Black Knights " Subscriber

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    It may be alignable.
     
  12. Soundslave

    Soundslave AK Subscriber Subscriber

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    Don't know that the receiver is worth spending that much money on. Is there anything I can do
     
  13. ConradH

    ConradH AK Subscriber Subscriber

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    There are a variety of adjustments that can be made without test equipment, but from your description those won't help. You need alignment and possibly troubleshooting. Where are you?
     
  14. Soundslave

    Soundslave AK Subscriber Subscriber

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    Kansas City
     
  15. Soundslave

    Soundslave AK Subscriber Subscriber

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    I do have a Scope, Function Generator, DVM and Distortion Meter
     
  16. ConradH

    ConradH AK Subscriber Subscriber

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    You're well equipped, but will probably need a stereo alignment generator like a Sencore SG series, Leader or ST 1000A to get the job done. Even an old Heath IG-37 would get you very close. I don't know how similar it is to the 620, but you can get an idea of how it's done from this- http://conradhoffman.com/Yamaha_CR_620_align.htm
     
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  17. avionic

    avionic " Black Knights " Subscriber

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    A freq. counter would be handy as well.
     
  18. rcs16

    rcs16 Super Member

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    Location:
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    The center tuning meter adjustment usually does not require any test equipment. You usually tune to a quiet part on the dial(only white noise) and adjust the discriminator(quadrature or ratio detector) for a zero across the meter. You have to have the correct nylon tuning tool for the core that is used. be careful that these transformers have usually 2 cores, one for a zero and one for linearity. One usually adjust both of them. For linearity, one uses as IF sweeper to set "S"curve buty best method is to measure mono THD and adj for lowest THD.
    The signal strength meter is adjusted with a set input RF level.
    The signals to these meters usually go through switches, so they should be cleaned as well as part of a tuner tune up.
     
  19. willyrover

    willyrover Super Member

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    Location:
    Hamilton
    Is D201 good?

    (Between pin 16 of IC201 and pin 11 of IC301)
     
  20. Soundslave

    Soundslave AK Subscriber Subscriber

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    D201 is good, adjusted the discriminator and vr301 and everything is good. Thanks everyone for your help
     

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