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  • Rodgers 770 Cipher

    My Rodgers 770 has developed a problem which is perplexing me greatly. On the swell, the following stops have a cipher that has just developed:

    Bourdon doux
    Gedackt
    Nachthorn
    Blockflote

    For only these four swell flute stops, there is a "play along" cipher on only the key "f". Couplers engaged will cause the cipher to move to a different "F" on the swell (up the keyboard for the 16' coupler, down for the 4' and so on, but it ciphers only on an "F")

    Can you think of anything in common with these four stops that could give me a starting point? Anyone know what could cause a play along cipher only on one note of the scale?

    Any of your thoughts and theories are most welcome!

  • #2
    Hi,

    My guess is you have a problem in the diode gate board relating to the swell flute keyer. I have found it is somtimes a bad solder joint. The wiring to these boards is magnet wire, a real pain to work on.

    AV

    Comment


    • #3
      Well, for starters, these four stops are all drawn from the swell unit flute. But I'm curious as to how the flute keyer board would be affected by couplers. Are you saying that this "F" pitch sounds continuously, with or without any stops turned on? Or is it only when you turn on stops?

      Most ciphers in Rodgers LTG organs in my experience have been caused by faulty key contacts. There are two keying whiskers under each key, both performing the same function, but having two of them provides redundancy in case one of them should fail or stutter. Now and then, one of these whiskers will break loose at the back end and start to droop until it touches the buss bar, producing a cipher.

      If that's not it, you might have a defective encoder chip somewhere in the small pc board that runs along the rear of the keyboards, or on the multi-function board inside the CPU enclosure. Or a bad solder joint or other mechanical cross-connection on the swell flute keyer board.

      --------- Arie V and I were typing at the same time, and he mentions the keyer board too. Take a look at it first!

      It also occurs to me that one of the 4094 chips on the keyer board could be malfunctioning, but if so it ought to be a single pitch ciphering, and which pitch it is should not change depending on what stops are on or what couplers.

      Again.... See the questions I posed at the top of my comment. Answering those may lead to a more specific diagnosis.
      John
      ----------
      *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!

      https://www.facebook.com/pages/Birds...97551893588434

      Comment


      • #4
        Thanks Jbird,

        There is no constant Cipher at all, if I do not pull one of the mentioned four swell flute stops, everything works fine. If I use one (or all) of those four flute stops, everything plays fine.....as long I I do not play an "f". There is no constant cipher, even when the suspect stops are engaged. you only hear it when you play an "F". The true sound of the stop can be heard, but the cipher on the F notes play along also. Does that help at all?

        Many thanks,

        Comment


        • #5
          Look at the keyer board near the F that plays--it could be the shift register/latch IC or perhaps a bad solder joint/short.

          Comment


          • #6
            I think what you're hearing is an unwanted tone that has become attached to one of the pitches of the flute keyer. You say the flute tone itself can be heard, but there is something else going on as well when that note plays.

            Best way to determine exactly what is happening is to use just one of the affected stops, and I suggest the 8' stop with no couplers in use. You should find that just one of the F keys now produces this strange sound. You can verify by turning off the 8' stop and turning on the 16' stop, then checking to see if the errant note has now moved one octave up on the keyboard (same pitch, just different position on the keyboard). Or 8' off and 4' on, and the bad note will have moved down one octave on the keys.

            If so, then what you have is a a keying fault of some kind, and it is not a contact issue as I first suspected. The trouble is almost surely going to be on that swell flute keyer board. With the 8' flute stop turned on, count up the keyboard, both white keys and black keys, until you come to the bad note. For example, if it is F in the first octave of the 8' stop, it is note #6. If it's F in the second octave, it is #18. F in the third octave is #30, etc.

            Now, you can look at the keyer board and see that the notes are numbered. Find the number that corresponds to your faulty note and check all the wires, traces, and soldering associated with that number and the ones around it. You may well find a spot of solder that is cross-connecting the musical pitch with some other electrical signal on the board, such as a data or clock line, thereby introducing a harsh un-musical sound.

            I remember having something like that once on a Rodgers analog, and it took a long time to find it. Might have been a bit of a wire whisker sticking out from a soldered-on connection. Of course it could also be a defective 4094 chip or defective keying diode on that note, but I'm inclined to think not, since you say you CAN hear the normal sound along with the bad sound.
            John
            ----------
            *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!

            https://www.facebook.com/pages/Birds...97551893588434

            Comment

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