Forum Top Banner Ad

Collapse

Ebay Classic organs

Collapse

Announcement

Collapse
No announcement yet.

Rodgers 760 volume fluctuation

Collapse
This topic is closed.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Rodgers 760 volume fluctuation

    For a few select stops on my Rodgers 760, the volume levels on the Great Mixture and Great Flutes seem to be fluctuating. I first noticed this several months ago when the balance on some of my preset registrations started to sound different. It is not a change that could be noticed in a single practice session at the organ, rather the volume levels may sound one way for several days or even weeks, then they would suddenly get louder or softer. So far, I have not been able to pinpoint any pattern to the occurrence and the changes appear to be random.

    Is there any relation to the problems expressed in the 755 trumpet thread?

  • #2
    Many stops on the 760 (605, 625, 640, 645, 650, 705, 740, 745, 755, 770, 780, 830, and I'm sure others) have two volume levels for many of the unit stops (swell flute & principals, great flute & principals, some pedal stops, unit trompette): identified as "loud" and "soft". The volume level for "soft" is adjusted by a potentiometer on the individual keyer boards, but the individual stops (some, but not all) are selected by the organist from the front of the console by going into a programming mode (similar to setting the chiff levels, octave by octave).

    These settings along with the chiff levels and other user programmed features are stored in a memory that has a battery backup. If the batteries are weak, it can cause the organ to lose the setting.

    Does the organ have power to it all the time? Maybe it's on a circuit breaker that gets turned off? If the battery drains, memory is lost, and you go back to the factory presets. As long as the organ is on, though, memory is maintained, so you could set levels for a session, and then when power is off and batteries are drained, the factory preset comes back.

    Another possibility is an intermittent connection or pot on the soft setting for a keyer or several of them. The "soft" setting is just an electronic clamp to limit the keying voltage when the note is keyed softly.

    Comment


    • #3
      Toodles,

      Yes, the organ is plugged in all the time and the circuit breaker remains on as well. If the battery drains would it also affect registrations stored in the combination action? There have not been any problems with the combination action forgetting registrations.

      I could try giving the pots a sweep. Are there any in particular which should be examined first?

      We had some large temperature and humidity swings late in the summer and early fall, could this be a cause?

      Comment


      • #4
        If the batteries are dead, but if they are weak it might affect some memory chips and not others.

        The best diagnosis of the problem will come from the most detailed description of the problem--it affects these voices, but not these others, etc.

        I doubt it is a pot problem unless it is an intermittent solder joint or something like that. But the pots to check are the ones that on the voices that fluctuate. You probably need to write down issues as you observe them rather than just go from memory.

        Temp and humidity are not likely causes.

        Comment


        • #5
          I will make more detailed notes on the specific voices. The frequency of the changes, often spanning long periods of time at a single level, has made observation challenging. Especially since sometimes the changes are subtle. The most noticeable stop has been the Great Mixture IV, as it has had the greatest difference between loud and soft levels. When it is loud it is very screechy and sticks out far to much in ensemble registrations.

          Comment


          • #6
            The tech manual indicates that the Great Mixture IV cannot be set for loudness level, but I suspect the manual is wrong (they frequently are on this particular point--maybe it was originally planned one way and then changed but the manual info was never corrected?).

            See if you can set the Mixture to the lower volume level. But maybe the overall Great principal is too loud or the individual pitches need to be balanced better. The 8' Principal is always at the loud setting (and the Gemshorn is always at the soft setting), so switching between these 2 gives you a quick reference as to the correctness of the loud/soft soft difference. From there, you can decide if the 4' and 2' balance correctly with the 8' Principal. At that point, you should be able to hear if you are happy with the overall volume setting for the principal keyer. The mixture then should fit in without being too strong in either the loud or soft volume level.

            Another balance check is that the Great Trompette 8 and Mixture IV should work together without either dominating. The reed/mixture chorus: all reeds, all mixtures, coupled to the great should be a blaze of sound but no distortion, no screech.

            Comment


            • #7
              Some more observations:

              Opened up the organ to do some tuning and misc maintenance. The organ has always had very slight white noise from the speakers, it is a very low level that is negligible when playing music - so not an issue. However, I noticed the volume level of the noise seemed to flip between louder and softer levels several times, as I was sitting right next to the speaker. This was happening when no keys were being depressed or sound played through the system.

              Tried a few stops and the volume level seemed to be slightly changed - you have to really pay attention to it in order to notice. A General Cancel, and sweeping the expression shoes several times seemed to stabilize the issue.

              Comment


              • #8
                Perhaps there is a tweeter issue on the speaker carrying the unit principal. If the tweeters are intermittent, or if the pot that adjusts their level is flaky, that might cause a rather dramatic and abrupt change in apparent brightness and level of the mixture, and might also have an effect on the white noise that you mention.
                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


                • #9
                  The speaker carrying the unit principal is a Rodgers M3 cabinet. Where would the tweeter pots be located for it?

                  Comment


                  • #10
                    The Rodgers M3 speaker cabinet contains one of the JBL "bullet" tweeters. Best I recall, since that cabinet does not have an open back, there would be a tweeter pot located somewhere on the front panel, probably close to the tweeter. It might be accessible through a small hole (about 1/4" in diameter) drilled in the front panel, and you would need a slender flat screwdriver to adjust it. I'd sweep it back and forth numerous times through its range while you have some mixture notes blocked down so you can hear what it does. You may discover that it has developed a dead spot right where it sets, and you can sweep it back and forth until the dead spot clears up, or else re-position it just a tad higher or lower than where it presently is set.
                    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

                    Working...
                    X