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Allen THEA.15

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  • Allen THEA.15

    New to this forum. I am trying to help an organist get her organ to operate correctly. I have not much musical background but lots of electronic and mechanical background. She will supply the talent to tell me what does not function properly or is weak.

    At this point I know the organ tag says it is an Allen THEA.15 serial no. 51551. I have no manuals or schematics.
    i believe that the tag says it is a theatre type home organ and the 15 may refer to the power amp output. I know it has 2 keyboards or ranks. I know it has tab paddle type stops. It has one volume pedal in the center of the console with the power amp sounding right with plenty of power. There area set of 5 preset buttons with a clear button below each keyboard. When pressed a corresponding lite shows up on the right side panel. BTW this has a curved layout.

    Most of the functions work with exceptions of a few issues.

    Couple stops do not work.

    A key on the swell rank does not produce a pitch, and a couple of others sound weak.

    One foot key does not produce sounds.

    Can someone tell me more about this specific organ like?

    What year was it made?

    Is it considered a digital organ?

    How many pipes does it have?

    How do the presets work and can the organist configure them?

    Where can I find an operator or user manual?

    Where can I find schematics and diagrams so I troubleshoot and understand the internals of the organ?

    Thank you for any information supplied and let me know where in the forum I should go to post if this is not correct

  • #2
    I'll take a stab at it. The Allen Theatre 15 organ is a transistor analog organ built around 1962. It is not digital. I doesn't have any pipes. It has several transistor oscillators though. If the organ you are working on is a TH-15, it is possible to buy the technical manuals and schematics from Allen for $95.

    As always, pictures (or videos) are invaluable and will help us confirm the organ's identity and help with troubleshooting. There are several members on the forum who have done extensive work on older analog Allens. Hopefully, they will chime in.

    I will say that Allen organs are usually fairly straightforward to understand. It shouldn't be too difficult to find where components might have failed.
    Last edited by samibe; 01-14-2019, 07:42 PM.
    Home: Allen ADC-4500 Church: Allen MDS-5
    Files: Allen Tone Card (TC) Database, TC Info, TC Converter, TC Mixer, ADC TC SF2, and MOS TC SF2, ADC TC Cad/Rvt, MOS TC Cad/Rvt, Organ Database, Music Library, etc. PM for unlinked files.


    • #3
      Do get the service material from Allen. While an analog Allen is a relatively "simple" machine, it doesn't work just like any typical old organ, totally different in concept from the old Hammond, Baldwin, Wurlitzer, Thomas, and other brands of the same era. And the TH-15 is a rather unique animal even among Allen analogs, as it builds upon the "unit flute" concept by providing a secondary set of voice filters that are "piggy-backed" onto the flute oscillators to provide authentic reed and string voices. This is a somewhat complicated bit of circuitry that needs to be understood properly before you can do repairs on it.

      That said, many simple repairs can be accomplished by simply cleaning up an older organ like this. Dust, debris, corrosion can be removed from metal mating surfaces, plugs and jacks and other connectors. The hundreds of key contact wires will eventually have to be cleaned -- by hand, one at a time, no "spray away" solutions! -- as well as the stop tab switches and other control devices. Getting everything cleaned up and mechanically in order might go a long way toward fixing it.

      Another common issue with analog Allens is the failure of the keying capacitors inside the generator chassis. These are usually arranged in a long row, from one end of the generator tray to the other, just underneath the inner lip of the metal can. (NOT to be confused with the tuning capacitors, which are on the outside of the generator assembly.) These range in size from about 2 mfd up to about 30 mfd, and they serve to give the oscillator a "soft start" when each pitch is called for by a key contact closing. These caps are essential to the oscillator's running, so when they lose much of their capacitance, the oscillator will no longer speak, thus you have dead notes.

      If you turn the pedalboard upside down you will see that the keyswitching under there is quite simple, with a brass shorting bar that must come into contact with a set of four wires. Even though there are four of the wires, it really only amounts to a single switch, as two of the wires carry +14 volts and the other two are connected together and go back to the gang switch that feeds the pedal generator system. The wires are doubled up for reliability/redundancy. The dead pedal note could be due to the brass shorting bar needing adjustment with the attached screw, to bring it close to the wires. Or the wires could be mangled or bent or just dirty.

      Beyond those things, the circuitry gets more complicated, and you need to study the service literature carefully to understand how it works. It isn't rocket science, but it does make for some excellent reading and will bring you a lot of satisfaction if you are able to start solving the little problems one by one.

      BTW, you will want to brush up on organ "terms" so you can accurately describe your problems. For example, the two keyboards are called the two "manuals." The term "ranks" is only applied to either ranks of pipes in a pipe organ (sets of 61 pipes that make up a complete stop) or ranks of oscillators, of which there are generally just two or three in even larger Allen organs. A "rank" of oscillators is a complete set of somewhere between 37 and 85 arranged all in the same chassis, creating the basic pitches for a range of notes from the deepest 16' pedal tones to the highest manual pitches.

      *** 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!


      • #4
        You don't need the operator's manual particularly. The service literature should be quite clear about what the functions are. There are block diagrams of the various systems in the analog service manual, and they are so old they are hand-drawn and lettered! (Unless they've revised and re-done them with modern drawing software.)

        Could be a bit obscure until you study it out, but once you wrap your brain around the theory behind these organs, the block diagrams will make sense.
        *** 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!


        • #5
          Thank you Sam and John! What an education already. I'll will get conversant with the organ terminology. I have contacted Allen Service and they do have a document packet for this unit. I will order one.

          Does any one know if there is block diagrams that show the various assemblies within the organ to help a novice like me locate them. Until John pointed it out to me, I that it had pipe system inside.

          Service mentioned they do not have an ‘operators' manual. Does on need to have that manual to repair this organ.

          Thank you for the quick responses and look forward to get it up and sounding great again (possibly with the forum member experience and responses).

          Last edited by myorgan; 01-19-2019, 09:16 AM. Reason: Duplicate post.


          • samibe
            samibe commented
            Editing a comment
            The Owner's Manual might be included in the document packet.

        • #6
          If it says redirected int the blower room, where does that take you.




          • myorgan
            myorgan commented
            Editing a comment
            Not sure what you're seeing, Craig, but the Blower Room is where posts with questionable content are directed. This thread is NOT there.


          • Admin
            Admin commented
            Editing a comment
            What myorgan said. Where are you seeing redirected?

            Threads are redirected to other channels in the Forum when posted in an inappropriate area for their subject. Like posting a question on a Baldwin Fun Maker in the Classical Pipe Organs channel.

            In that case, a moderator will move that thread to the appropriate Home Organs channel and leave a redirect notice to it's new location where it was originally posted to alert those following that topic to its new location. Clicking on that notice will take you to it.

            Channels under the Blower Room category are general purpose areas for subjects that don't quite fit elsewhere.

            If you originally started this thread in the Blower Room, it was moved here for greater visibility, and will show as redirected in the Blower Room.