Piano, Organ, and Keyboard/Yamaha organ HS-7T

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Question
Hi Thomas,

The Yamaha organ HS-7T can only produce a buzzing sound, however,
the rhythm plays. The buzzing sound can also be heard when switched to the headphones. All the lights on the keyboard are lit. I checked all the capacitors visually and there are no bulging, burned nor burnt smell.

I have this last 1987 and I guess made between 1984 to 1987.

Will you be able to determine where the problem is?

Answer
Hello Eli!  Judging from the age of the organ, I suspect the problem involves the filter capacitors in the power supply.  When the capacitors go bad, they allow DC ripple to pass into the organ's circuitry causing an audible 120Hz buzz.  

Capacitors can either open or begin to behave more like resistors.  When the latter happens, fuses start blowing and parts start burning.  However, when capacitors open, things stop working and a buzzing is heard for lack of filtering.  I think you have open capacitors, which means you are not likely to find bulging or hot capacitors.  A check with an oscilloscope at the power supply outputs would confirm the presence of DC ripple.  If you do not have a scope, then a voltmeter set on AC would read an AC voltage on the DC output which would be a dead giveaway.  

Piano, Organ, and Keyboard

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Thomas Britanyak

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I am a full time organ/piano technician who has been actively involved with the design, building, repair, maintenance and installation of organs and pianos for 35 years. I began as a keyboard instrument apprentice and hold degrees in music and electronics. If you need a piano's date of manufacture, please go to http://www.pianoexchange.com/howold.htm or http://www.bluebookofpianos.com/pianoage.html I am happy to answer musical or technical questions, however, I CANNOT offer appraisals on pianos or organs. Please do not ask what an instrument is worth. For this service please contact an experienced local appraiser or try the following links: https://mmm1100.verio-web.com/blueb1/appraisal.html or http://www.57piano.com/questions.htm

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I am a full time organ/piano technician who has been actively involved with the design, building, repair, maintenance and installation of organs and pianos for 35 years. I began as a keyboard instrument apprentice and hold degrees in music and electronics.

Education/Credentials
I am a full time organ/piano technician who has been actively involved with the design, building, repair, maintenance and installation of organs and pianos for 35 years. I began as a keyboard instrument apprentice and hold degrees in music and electronics.

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