Yamaha A-720 Potmeter question

Discussion in 'Yamaha' started by Addict1337, Feb 22, 2017.

  1. Addict1337

    Addict1337 New Member

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    I've decided to repair my A-720 witch only plays sound on one side (If I up the volume the other side starts tho).

    After a bit of fiddling around I noticed that the balance potmeter is definitely broken/working poorly.
    So I decided to replace all of the potmeters since i'm opening the unit up anyway.
    However I haven't been able to find any potmeters that will fit, or that have an equal amount of 'K'.

    I wrote these values down, witch are the potmeters that i'll replace:
    62 2P S-40K
    0-100K
    61 8F 250kMN
    300K
    60K 622P (volumeknob)

    I'm fairly new to amplifiers, not to soldering tho.

    Maybe someone on this forum can help me out with this one :)
     
  2. avionic

    avionic " Black Knights" Subscriber

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    Potentiometer---:thumbsup: Welcome to AK... Plan B " start shopping for a donor candidate.":idea:
     
  3. Addict1337

    Addict1337 New Member

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    Really :( ?
    I would really like to have new ones since this amp is (as you probably know) is really old one, and I guess most of them aren't working properly anymore.
     
  4. avionic

    avionic " Black Knights" Subscriber

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    PM Clinic-audio...Patrice might be able to help you out.
     
  5. avionic

    avionic " Black Knights" Subscriber

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    Location:
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  6. avionic

    avionic " Black Knights" Subscriber

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    According to the service manual
    VR201 --->HS312120 or HS411920 yamaha part #'s (balance)
    VR203 --->HS320700 or HS420340 yamaha part #'s (volume)
     
  7. Addict1337

    Addict1337 New Member

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    Thank you guys very much for the replies so far.
    I've dropped Clinic audio a message, and have been able to find a website who has 35mm potentiometers with the right amount of "k" for at least the 250k potmeter.

    Are there parts I can use on this website? Is this the right one, since they have a lot of kinds of potentiometers there:

    http://www.futurlec.com/PotRot.shtml

    I don't really care if I have to order each individual potmeter from different websites, as long as I get them :)
     
    Last edited: Feb 23, 2017
  8. clinic-audio

    clinic-audio all on YAMAHA untill 1990

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    Hello Addict1337

    Sorry but where are you ?

    Please send me picture of the defective one . Value is not enough for me to find the right one .
     
  9. Addict1337

    Addict1337 New Member

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    Hi clinic-audio,

    I will take pictures tonight of the potentiometers i'd like to replace :)
    Tanks in advance.
     
  10. Addict1337

    Addict1337 New Member

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    I've been fiddling around a bit more, and noticed something.
    When I bridge the Balance knob for the right channel, the sound starts playing again! :)

    I guess i'll just solder them together, who needs balance anyway :)

    Also I cleaned out the remaining potentiometers, and all is working well now.

    Thanks very much for helping everybody.
     
    Last edited: Feb 23, 2017
  11. avionic

    avionic " Black Knights" Subscriber

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  12. Addict1337

    Addict1337 New Member

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    I guess you want me to send a photo of the defective part? :)
     
  13. clinic-audio

    clinic-audio all on YAMAHA untill 1990

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  14. Addict1337

    Addict1337 New Member

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    I've been to an Audio expert today.
    Het cleaned out 1 of the potentiometers, the other one was done for so I need a replacement for that one.
    For now I bridged the connections of this potentiometer on the circuitboard so I can still listen to music.

    [​IMG]

    [​IMG]

    Thanks in Advance :)

    (This is how it's looks now without the potentiometer :( )
    [​IMG]
     
  15. clinic-audio

    clinic-audio all on YAMAHA untill 1990

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    OK
    I come back to you as soon as possible
     
  16. Addict1337

    Addict1337 New Member

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    I guess you didn't find it?
    Kind regards.
     

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