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Conn 721

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  • Conn 721

    This is my first post. - I wish to restore a Conn 721 which basically works but there are quite a few stops not working and I would like info on initially opening it up and suggestions re repairs. I assume most of the problems will be (hopefully), bad switch contacts etc. I have had some experience working on a smaller Conn which has faulty rocker switches but I cannot find a source for these anymore, but that's another issue. I must admit though that I'm impressed the way these things are made.

    However, as these organs are not young, I would appreciate any suggestions such as voltage checks, any vulnerable electros etc. and if there are service manuals available for download. (preferably free !)


  • #2
    Conn's are very easy to clean with swabs and alcohol. They also tend to require a little playing time before they function at their peak. A service manual is probably not available free but they are cheap. Watch for one on ebay.


    • #3
      In the USA one source of Conn manuals and parts is Organ Service of Marengo, INdiana. They are on the internet and have a phone number but there are two organ service co, get the right one using a search engine.
      Bad switch contacts are a ritual of cleaning, and cycling. Other contacts within organs built with transistors or IC's need removal and replacement after a decade or so. Be careful to bend back latch pins instead of breaking them, use a lot of light. contact cleaner of the aliphatic hydrocarbon sort can't hurt, I buy mine at the lumberyard. Other names are hexane, heptane, petroleum distilllates. It should evaporate and not leave a residue on a plastic bag. Do not use non-flammable borinated hydrocarbon contact cleaner from the electrical supply, these dissolve PVC and styrene plastics used in consumer electronics. These non-flammable cleaners are about $28 a can so it is easy to miss them.
      Warning aliphatic hydrocarbon cleaners are flammable, no smoking, open flame, pilot lights, electricity turned on or off within 10 m. Set up a fan before spraying to dissipate the fumes.
      Frequently old organs will work for a week or four while the water evaporates out of the electolytic capacitors past the cracked rubber seals. When shorted these can cause burning of the rectifier vacuum tube or resistors, or simple failure to function due to low power supply voltage on the local card . When just low value they can cause low power, insufficient bass, insufficient treble, hum, or symptoms that come and go as the organ heats up. See this generic thread about changin transistor organ e-caps and some connector cleaning tips also.
      Have fun. Analog transistor organs are simple enough to learn transistor circuit repair on, and can replace a $10000 instrument with a $100 salvage purchase and $50-200 in commonly available parts.
      city Hammond H-182 organ (2 ea),A100,10-82 TC, Wurlitzer 4500, Schober Recital Organ, Steinway 40" console , Sohmer 39" pianos, Ensoniq EPS, ; country Hammond H112


      • #4
        Hello, Org;

        Your 721 Artist was introduced in 1969 and uses individual transistor oscillators in the tone generators. It may have the dreaded vinyl keyswitch busses, which could account for some weak or dead notes on the string, reed or diapaon voices (not the flutes).

        Having serviced Conns for over 55 years, I will be happy to help you with various problems. I suggest you send me a Private Message (AKA "PM").

        I have an original 721 service manual for sale from my collection. It is an original Conn factory publication, not a scan or xerox.

        . . . Jan
        the OrganGrinder


        • #5
          Thanks for your encouraging replies. I will follow up your links.