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Conn 627 Rhapsody Problems

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  • Conn 627 Rhapsody Problems

    Been working here and there on my old 60's all tube Conn and its got a few bugs still. I don't have a schematic for this one so just doing what i can with it. Here are a couple pics of the metal boxed percussion circuit which is pretty noisy even after I replaced the known electrolytics but still got the crackly pop static hiss stuff that comes and goes whenever you activate one of the tabs.. The white Mallory's and the little black ones.. are these plastic molded paper ones? I'm pretty sure the reddish brown Good-Alls are mylar film and are normally very reliable..

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  • #2
    Messing around this weekend with the scope i think i pinpointed the problem area.. In the pictures above the left pan has the fun master circuit in it and the right one has the circuit for the brush, cymbal, wood block and bass drum noises and this is where the trouble is.. Below is a pic of what i think is a noisy transistor right next to the master volume pot which i was also getting some static out of .. Even after cleaning it it doesn't change the volume any but it did make a lot of the pop and crackle go away.. Does anyone have any knowledge of a replacement for this transistor or trim pot? The transistors aren't marked just a colored dot on top, yellow.. which is the case here or red, green, orange.. I can't seem to get a hold of organ service anymore and their website is down so no schematic, tried Ebay but no luck on this model...

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    • #3
      Working on the Conn this weekend i realized i missed the markings on the transistors, pretty tiny but they are there and its a common number so it was easy to cross reference. The trim pot though i just took out and tried some different resistor values till i got a good sweep from low to high on the volume control by the percussion tabs.. A 56k works well to my ears.. Everything seems normal and quiet just need to clean the whiskers and keying rods but these are already in pretty decent shape.. The reeds are coming through well..A couple extra pics of the organ as well.. :-)

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      • #4
        Does anyone know how the accompaniment percussion normal/divide tab is suppose to function?

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