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Any pots on an Allen T12

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  • Any pots on an Allen T12

    I play a Allen T-12 on a regular basis and was wondering, are there any pots that I could change to deepen the vibrato and up the volume on the bass notes? I know I'll never get the Leslie effect with what I'm working with (no gyros either) but I'd really like a better vibrato than what I have. I would also like my bass to stand out more than it does, hence the pedal question.

  • #2
    On the generator chassis you should see some little miniature pots that control the volume of the lowest two octaves of pitches. Each pot controls 6 notes, so you can't adjust note-by-note, but you can boost the volume of those lowest notes if you need to do that.

    The vibrato on a T-12 is produced by the rotating speakers, so there is no adjustment for that. If your T-12 has had its gyros replaced with stationary speakers, you probably have a Trem II electronic tremulant generator. It has adjusting pots on top of the chassis for speed, depth, chorus, etc. Block down a note and adjust the pots while listening to see what happens.
    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

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    • #3
      Are there really rotating speakers? I heard a noise of some sort when I flipped the vibrato tab but didn't realize there was a gyro in there. Is the generator accessible from the top or do I have to take the back off (Which I really don't want to do).

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      • #4
        If you hear a mechanical noise when the vibrato is on, you must have a gyro. It might not be turning due to a broken belt or something, but should be easy to fix if you take a look at it.

        Generator is easily accessible from the back. Just raise the top lid, turn the two little clips that hold the back in place, and the back will simply tilt out. The generator is the wide horizontal chassis about mid-way down with all the tuning controls. Look carefully and you'll see some tiny pots marked "C0 - F0" and "F#0 - B0" .... These adjust the two halves of the bottom octave of the 16' stop. Be sure not to boost it too much or you'll get distortion or rattle the speaker.

        There may be another pair marked "C1 - F1" and "F#1 - B1" which will adjust the lowest 8' octave.

        Don't be afraid to tinker. Just be sure to listen while you're doing it.
        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

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        • #5
          Jon thanks for the help. I took the back off, adjusted the knobs.... no sound at all came out. It scared me half to death. But after adjusting the knobs a few more times, I finally manged to get a halfway decent bass (for an internal speaker anyway). Since then, though, I noticed that the pedals just below middle C sometimes sound real fuzzy and then drop off completely. I'm not sure why. Do you know? Now a new problem. My pedal volume is better but the manuals sound quieter. Do these pots also adjust them in some way. Either way, I want drawbars and a Leslie speaker more than ever now. These silly old stop tabs and these puny internal speakers don't do a thing for me creatively speaking. But.... the old ladies who listen to me like the organ so I suppose that's the most important part.

          One more question. If I turn the vibrato and tremolo off, the organ sounds like its playing through different speakers then when they are on. Why?

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          • #6
            On the T12, the "gyro" runs all the time. Turning on Vibrato or Tremolo simply turns on the speaker in the gyro. (You might also see that, though there are two speakers on the rotor, only one is connected. I'm guessing the 2nd one is simply to balance the assembly.)

            Tremolo vs. Vibrato does not change the speed. Selecting Vibrato simply adds a capacitor to the gyro speaker circuit, making the effect deeper("more bassy").

            Greg

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            • #7
              Makes sense. I do notice a deeper sound when the vibrato is on. I wonder why there's no control to turn the gyro off or put it on slow motion. Too much like Leslie maybe?

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              • #8
                You may need to "exercise" the little mini-pots to get them to make good contact. If the pedal notes sometimes drop out completely, the pots may have dead spots, but turning them all the way through their range of motion a number of times will often clean them up.

                Don't be afraid to turn the pots, just be aware of which notes each one affects, then listen to those notes to make sure you don't make them too soft or too loud. There should be a smooth transition between the upper and lower portions of each octave, and from the lowest octave to the next octave.

                The volume control knob on the amplifier can also get dead spots or become erratic, so turn it back and forth a few times, then set the knob to give you an acceptable level in the middle of the manuals. Then adjust the bass to match.

                You can't hurt the organ by playing around with these controls. Just be a good listener and make sure to set them so that things are well balanced between the manuals and the pedals.
                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

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                • #9
                  Thanks John. Can you tell me which pot controls the overall volume of the organ? Also why is it when you have a certain stop tab down, it doesn't change the sound? On its own it plays so it's not a dead contact.

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                  • #10
                    Overall volume is controlled by the volume knob on the amplifier. It will be a plain aluminum shaft on the side of the amp, no knob on it at all. May be hard to explain to you what the amp looks like if you don't have any particular knowledge of electronics. It is a rectangular unit maybe 6" x 10" with an RCA connector going into it and speaker wires attached to a small terminal strip. It probably sits in the floor of the organ console just to the left (as you are looking in from the back) of the expression pedal, or perhaps right under it. If your T-12 has no speakers in the console, the amp might be in the speaker cabinet itself. The speaker cabinet may also have a big chassis that serves to control the motor speed, so don't be confused by it, if there is one.

                    The reason some stops appear "dead" -- this little organ is just a one-rank unit organ. The only tones produced are in fact flutes. Most of the stops, such as the diapason, strings, reeds, are simply combinations of various flute pitches. When you turn on -- as a good example -- the "String Diapason 8" in the great division, that one stop actually turns on every single available flute pitch on the great to give a simulation of a String Diapason. Therefore, once you have turned on that stop, turning on any more stops in the great will not add anything at all, so the rest of the tabs will seem to be "dead" though if you turn them on individually one at a time you'll find that they all work normally.

                    Same thing in the swell division with the Trumpet stop. It turns on a variety of pitches to simulate a trumpet, so many of the other tabs will seem to be dead once the trumpet is on.

                    So, it's a small and limited little organ, but I have heard people make amazingly beautiful music with them.
                    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

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                    • #11
                      Hello, Jon, Mak and all;

                      If you are involved with any model of Allen Analog organ, I suggest you make a small investment in my new book ALLEN ANALOG ORGANS
                      and thought you might be interested in knowing about it.
                      It's a compendium of information collected over the years from several sources, namely:
                      • Allen Organ documents
                      • The Electronic Organ Reference List
                      • out-of-print books on electronic organ technology, all assembled in a 24-page 6-ring loose-leaf binder. Much of this information has been out-of-print for many years. For a PDF brochure, email me at [email protected]

                      . . . Jan
                      the OrganGrinder

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