No (very faint) sound from Yamaha CR-1020

Discussion in 'Yamaha' started by cadwillow, Mar 20, 2017.

  1. cadwillow

    cadwillow AK Subscriber Subscriber

    Messages:
    14
    I have a Yamaha CR-1020 that I bought thinking it was "restored" and refreshed -
    but is now exhibiting the following symptoms:

    I first noticed that I could no longer hear the relay clicking after powering up.

    I pulled the cover to take a look. From watching another YouTube video, I gently pressed on the
    loudspeaker relay box (clear plastic cover) with the eraser end of a pencil and when pressing forward
    I could then hear it click. When I did this, I could then turn the volume all the way up, and hear the music coming thru faintly.

    A few minutes later during one of my manipulations of the relay box - the relay emitted a green spark ... and then no more sound at all - even at full volume.

    The relay has the following written on it:

    HC-HP DC 12V - F
    AP3421F
    7A1/6HP125 250V AC
    3A 30VDC 21217 H
    Made in Japan

    My first thought it to simply try and replace the relay. Second thought is what caused it
    to spark and shut off, and should I be trying to determine that - before simply replacing it....

    Any help would be greatly appreciated. I am kinda new at this - just learning about cleaning
    parts/pots, etc with Deoxit. If I am in over my head, will take it to a local tech - but wanted to see
    if maybe it was something within my capabilities first ....

    Thank you,
     
  2. mbz

    mbz Active Member

    Messages:
    422
    Location:
    Melbourne, Victoria
    First step, replace the relay. Second deoxit switches including coupler switch, faderlube all pots.
    The relay protects the speakers from excessive dc voltage. If new relay does not click then
    you have excessive dc, maybe caused by a blown transistor. The faint sound is probably caused
    by dirty contacts/switches.
     
  3. avionic

    avionic " Black Knights" Subscriber

    Messages:
    33,430
    Location:
    Fort Dodge, Iowa cornfield
    Not necessarily. Could be a power supply/protect circuit issue.Need to measure the DC voltage out of the amplifiers.
     
  4. avionic

    avionic " Black Knights" Subscriber

    Messages:
    33,430
    Location:
    Fort Dodge, Iowa cornfield
    Could be just bad solder connections on the relay or associated circuit.
     
  5. mbz

    mbz Active Member

    Messages:
    422
    Location:
    Melbourne, Victoria
    Yeah, I'm getting lazy, thought I'd dumb it down a little and caught myself out. All of the above are real possibilities, especially in a vintage amp/Rx.

    The relay control circuitry provides,
    - supervision of the dc voltage level of each channel. Should the dc voltage exceed a threshould (0.7-maybe 1.5V? depending on design) then the relay is deactivated and the amp/speaker
    connection is broken thereby protecting the speakers.
    - "suppression" of power-ON dc thump by waiting a few seconds (4-7?) before connecting the amp to the speakers, provided the dc voltage threshold has not been exceeded
    The power-ON dc thump still occurs, but it's during a period when the speakers are not connected.
    -"suppression" of the power-OFF dc thump by releasing the amp/speaker connection asap/before the power-OFF thump is generated.

    As above, the relay will not be activated if excessive dc voltage or there is a failure in the relay control circuitry due to faulty power supply, component or connection.
     

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