Piano, Organ, and Keyboard/Rodgers organ

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Question
Hello - I have a late 1970's Rodgers Trio 3 manual theater organ. Lately, while playing at a normal volume level, the volume will surge repeatedly to full volume all by itself. If I take my foot off of the expression pedal, the volume will hold steady, but if I adjust it even slightly, it will do the surge thing again.
Any ideas on this, and would this be something I could repair myself? I'm fairly adept at electronics. Thanks for your time, Rick

Answer
Hello Rick,  Usually the culprit is the mechanism in the swell shoe that sends a voltage variation to the electronics. There are two mechanisms in common use. One uses an incandescent lightbulb that shines light onto a photocell. By moving the shoe up and down, a shutter varies the amount of light that reaches the photocell. If the light bulb's filament breaks or becomes intermittent, an erratic volume results. The fix is to replace the bulb. Voltage is usually 12 to 14 volts.
The other mechanism for varying the volume is with a potentiometer. It is common for pots to become dirty and thereby become intermittent as well. They can be cleaned by spraying a tuner cleaner into the pot if you can find an opening. However, if the pot is sealed, you may need to replace the pot. Also, check that the three terminals on the pot are not touching each other. This can cause wild fluctuations in volume as well.  

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.

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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.

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