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  • Allen 301-3C background noise and help identifying components

    I am new to the forum and trying to help my small church get their organ working. I have years of experience repairing medical electronic equipment but no experience with playing or fixing organs. I am also learning the terms the terms/component names so I may miss-use or confuse terms so please feel free to correct me. The organ is connected to only 2 speakers that are not Allen organ speakers but worked fine before these problems started.
    The problem has been there for years and there have been lots of attempts made to resolve including bypassing elements. My current problem is low volume on the swell manual and hear is what I found and have done after reviewing the related forum posts.
    Cleaned/tightened all the RCA connectors, cleaned the pc board connectors, recalibrated both the 5V & 27V power (both were a little low). So far I found that the outputs from the flute & main DAC 2 output cables were crossed causing problems with the flute stops. Reconnected holders and seated the flutes are back. Found noise when the Main board (MOS Code A246FS) was touched due to the board not being aligned with the connector. Repositioned the board mounts and recleaned connections and connection is solid now. Also found that there is a power supply mounted vertical on the right wall that has been unplugged. Outputs are Mute,gnd,+15+12+5-15-5,Mute. When I plug it in the volume of the swell increases but there is a lot of background noise. This supply appears to power a large board on right end of the back side of the swing out rack. Also, the two power amps have 3 input connections which seems to be different that the pics of the S100 amps that I have seen. Can someone help with what this power supply is for, why it might have been disconnected and thoughts on isolating the problem?
    I have pics but need to research how to add pics via URL before I can post.
    Thanks for your time and feedback.
    Bill

  • #2
    I'm a long-time Allen tech and very familiar with the MOS models. But I don't recognize the power supply you mention. Perhaps it was added at a later time for some unknown reason. Pics of all the stuff inside the console would be helpful.

    The S-100 amps have three inputs and they are normally all used in a MOS organ. One is for the actual audio signal from the DAC board or analog celeste.

    A second input on the amp is for the expression pedal cell. That input is probably identified with a X on a small sticker or label.

    The third input is for the muting and "voicing" knob. That audio cable leads up to the "voicing" knob where it is also paralleled with the console sound relays that keep the audio grounded and thus muted until the delay voltage kicks in to open the relays.

    To post pics on this forum, you first start a reply to thread, then below and to the right click on "Go Advanced." Scroll down a ways until you see "Manage Attachments" button. Click on that, then follow the prompts to choose and upload your pics. The size of jpeg files is limited to some number of megs, but usually I have no problem uploading ordinary cell phone pics. You can only attach a maximum of five pics to any post, so you might have to do more than one post to get in all your pics.
    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
      Allen 301-3C Pics

      jbird604,
      When I click the 'Reply with quote' button no 'Go Advanced' button appears on my screen. Under Posting Permissions is says "you may not post attachments". How do I get permission to post attachments?
      Thanks,
      Bill


      Originally posted by jbird604 View Post
      I'm a long-time Allen tech and very familiar with the MOS models. But I don't recognize the power supply you mention. Perhaps it was added at a later time for some unknown reason. Pics of all the stuff inside the console would be helpful.

      The S-100 amps have three inputs and they are normally all used in a MOS organ. One is for the actual audio signal from the DAC board or analog celeste.

      A second input on the amp is for the expression pedal cell. That input is probably identified with a X on a small sticker or label.

      The third input is for the muting and "voicing" knob. That audio cable leads up to the "voicing" knob where it is also paralleled with the console sound relays that keep the audio grounded and thus muted until the delay voltage kicks in to open the relays.

      To post pics on this forum, you first start a reply to thread, then below and to the right click on "Go Advanced." Scroll down a ways until you see "Manage Attachments" button. Click on that, then follow the prompts to choose and upload your pics. The size of jpeg files is limited to some number of megs, but usually I have no problem uploading ordinary cell phone pics. You can only attach a maximum of five pics to any post, so you might have to do more than one post to get in all your pics.

      Comment


      • #4
        New users are not permitted to post attachments during the period they are on moderated status. This policy is to prevent the posting of unsavory pictures and files containing malware by spammers and hackers. I've removed you from the list of moderated users, so you should be able to add attachments now.
        -Admin

        Allen 965
        Zuma Group Midi Keyboard Encoder
        Zuma Group DM Midi Stop Controller
        Hauptwerk 4.2

        Comment


        • #5
          Allen 301-c3 Pics

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          • #6
            Allen 301-3C Additional Pics

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            • #7
              Your pics are worth a thousand words! Now I can see what you are talking about.

              It is obviously, as you said at first, a 301-3C from 1980. A nice example of the work they did in the closing years of the MOS1 era. As the dash three indicates, it has "second church" voicing, and the MOS board has a small piggy-back board, which could mean that it has the optional "frequency separation" feature, a nice enhancement that gave MOS organs some richness in the ensemble that was lacking in the original design.

              The analog celeste generator (the flat board with all the coils on it) produces a lovely string celeste without the need for a second high-dollar (at the time) MOS system.

              On top of all that equipment, which is standard on the 301-3, you have a pair of "Trem III" units which can create a very wild and interesting theatrical tremulant or vibrato, a much-desired option for those folks who wanted a deeper throb than the standard MOS tremulant could provide. So this is a very attractive example of the MOS organ system.

              At first I was totally puzzled by the large flat board with all the RCA cables connected to it, the one that's on the back of the panel holding the MOS board. But I believe the paper tag on it says "TAS" and so that must be a "Total Ambiance System" board, an early digital reverb sold by Allen. I have never before seen one of those installed inside the console of a MOS organ. The TAS unit requires the extra power supply (which I also have not seen before inside a console) and what I assume is the mixer board at the upper left corner of the same photo, mounted above the attenuator relay box.

              The two amps you show seem to be properly connected. You see an "X" input on each one for the expression cell, a "V" input that comes from the "voicing" knob and mute relay, and the signal input itself, which comes from, I suppose, the mixer board in this case, since the mixer comes between the DAC, the analog celeste, and the amp.

              For troubleshooting purposes, you can hook it up in the simplest possible manner. Run an RCA audio cable directly from each output of the DAC board straight to the signal input jack on an S-100 amp. This will bypass all the ancillary circuits -- the TAS, the mixer, the Trem units, the analog celeste -- and revert the organ to a simple plain vanilla MOS model. This will allow you to test all the stops and other standard organ functions such as expression and muting. If you get normal sound from all the stops with this simplified hookup, then you can be sure that your basic MOS system is OK.

              If you get no sound even after simplifying the hookup like this, there is something wrong with one of the five basic system boards, or possibly one of the amps or the mute system. But a report on the working condition with the simplified hookup will tell me a lot about what you need to do next.
              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


              • #8
                John,
                Thanks so much for the great response. Below are the results from my trouble shooting yesterday.
                As you requested, I connected the DAC outputs direct to the amp inputs as you requested and all the stops seem to work OK. I also found that the gain controls on the amps were turned almost all the way up causing some of the noise. I turned these down but wondering what the process is to set/balance the Gain Settings?

                While I was there, I started to trace the audio path and here is what I found. The DAC outputs connect to the Swell to Great relay box (small silver box); One output channel of the silver box goes to the Celeste Board, the Celeste board output to the top Trem II input, the top Trem Output goes to TAC input on the Mixer Board; The sec output of the silver box goes to the bottom Trem II input and the output goes to a TAC input on the Mixer Board. The mixer board is also connected to the TAS board with 4 cables. The outputs of the Mixer Board go to the amp inputs.

                I followed the outputs of each of the units by using the same bypass cable and was able to get signal all the way to the Mixer output. I did find however that the reverb was not working and was a source of noise. I cleaned all the connectors again with contact cleaner, cleaned/exercised all the pots and cleaned/reseated all the plug in chips and the reverb and delay switches seem to be working now.

                Also found that the Crescendo Pedal has an annoying mechanical squeak when pressed. It is there with power both on and off. It seems to be the contact wires rubbing against the wooden roller? I tried contact cleaner but that didn't help. Any thoughts?

                Also found that the ALT tabs (1-4) had no output until I reprogrammed each with a punch card. As soon as I shut off the power, the programing was erased. Is there supposed to be battery backup for this programming?
                Sorry for so many questions, your help is greatly appreciated.
                Bill

                Comment


                • #9
                  Bill,

                  The Alt. program is lost every time the organ is switched off. There is no battery backup. This is normal.

                  The contact wire squeak is not unusual but I have used Vaseline on the wood roller to help dampen the sound if too loud. This will be a dust collector over time so keep this in mind.

                  Michael

                  Comment


                  • #10
                    You can lubricate the crescendo mechanism with WD-40 or anything you want to use in order to get rid of the squeak. Vaseline on the roller is a good idea, but if the squeak is coming from a pivot somewhere, it may call for WD-40.

                    To balance the channels, set the "flute" channel so that you get a "comfortable" level from the Prinzipal 8 stop on the great with the expression pedal (NOT the crescendo) wide open. How loud is that? Well, not terribly loud. As loud as you think it would be to hear a single rank of pipes playing by themselves. Try setting the amp volume knob at about "8" as a trial, or at the red mark, if the factory put a mark on the knob or shaft. If the organ proves to be too loud or too soft, you can adjust it up or down as needed.

                    Now, to balance the other channel with the flute channel, you can start by setting the amplifier volume knob to the exact same number. But the actual test is to compare the volume of the Octave 4 stop in the great to the volume of the Prinzipal 8, which you established when you set the flute amp. The Octave 4 stop should very slightly softer than the Prinzipal 8. It is often hard to make that judgment when you are unfamiliar with organ stops, but just listen carefully and do your best. As an additional test, compare the 8' flute stop on the great (Hohlflote?) with the 4' flute stop on the great (Spitzflote?). These two stops should be about the same level, with the 8' stop possibly just a tad louder.

                    That gets the two amp channels in balance. Now, to set the volume of the pedals, adjust the bass boost knob on the DAC board at the flute channel output while playing a low pedal note with all the 32' and 16' stops turned on. You don't want the bass to be overwhelming or distorted, but substantial and bold. Again, a judgment call, best learned from experience. But you will soon know if the bass is too loud or too soft and can tinker with it until you get it right.
                    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


                    • #11
                      Thanks for your response and I will try these asap.
                      There are also three rocker of the six keys on the left of the Great that I don't know how to test or what to expect when they are pressed. (Pic attached)
                      When I press these down, I don't hear much of a change.
                      1) Random Motion Off;
                      2) Speech Artic. Off;
                      3) Great Tuning Sharp;
                      Attached Files

                      Comment


                      • #12
                        Some effects in MOS organs are rather subtle. "Random Motion Off" tab disables the "Random Motion" generator, which produces a very tiny but perceptible "jitter" in the tone. If you hold down a key in the fourth octave (with a rich stop like the Octave 4), then while holding down the key, turn the Random Motion on and off, you may be able to detect the subtle disturbances in the pitch.

                        Random motion was a set effect in early MOS models, but in the later ones, such as yours, it is adjustable over a wide range. It's possible that someone has turned the effect down to nearly nothing, in which case you may not be able to detect it at all. But its purpose is to break up the so-called "sterility" of the tone of early digitals by introducing this intentional "defect" in the pitch. It may not seem like much, but in a good acoustic setting this effect can make the difference between an organ sounding very bland and having a bit of "life."

                        Speech Articulation is also a subtle MOS effect that many people never notice until it is demonstrated. To hear it, turn on a 4' stop, hold down a key in the fourth octave, then play a STACCATO scale down in the lowest octave. If you listen closely, you will hear the pitch of the high note do a little "yip" each time one of the low notes is played. Turn Speech Articulation off, and the effect disappears. It too is adjustable, and someone may have set it to be very small. But if you listen you can probably hear it. It also aids in breaking up the sterile and dry tone of early digitals.

                        Great Tuning Sharp however, is a clearly audible effect. While holding down the C below middle C on the great, turn that tab on and off and you will clearly hear the pitch shifting. There are various uses for this effect, including a way to make a very nice "celeste" on those small MOS models without a celeste generator. But playing with that effect enabled will produce a distinct detuning between the great and the other divisions, which many people find makes the sound more "realistic" -- pipe organs are always a bit out of tune, so this effect lets the MOS organ appear to be more "pipe-like" in tuning!
                        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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                        • #13
                          Thanks for the detailed responses and with your explanations, I was able to detect the Speech Articulation and the Great Tuning Sharp effects but not the Random Motion. I am fine with these now.
                          I have gone through each channel checking the output by components from the DAC to the Amps and have found that the all seems to work fine up to the TAS Mixer Board. When this is connected there is noticeable distortion. I did find that on the TAS Control board there is an overload lamp that is on all the time? I have attached a picture of this board. Any thoughts?
                          Because the TAS is a problem, I have bypassed all the TAS boards for now. The current configuration has the DAC Flute Output connected to the ‘Sell to Great Attenuator’ Flute Input, The Attenuator Flute Output goes to the Celeste Board input, the Celeste output to the Flute Trem II Input and the Flute Trem II output to the Flute Amp Input. The DAC Main output connects to the Main Input on the Attenuator box, the Attenuator Output to the Main Trem II input and the Main Trem II output to the Main Amp input. (This bypasses the TAS Main board, Controller board and Mixer board and I have unplugged the TAS power supply for now)
                          When I tried to go through the process to balance the Amps using the process John provided in an earlier post, I found that the Pedal volume was controlled by the Main Amp rather than the flute amp? Also, neither of the Bass Pots on the DAC II board had any noticeable effect on the Pedal volume. Not sure if there is still something connected incorrectly?
                          I was also wanted to check if the Celeste Board being in the Flute Channel is correct?
                          Thanks for all your help!
                          Bill
                          Attached Files

                          Comment


                          • #14
                            If the overload lamp is lit, that probably means that the input level is too high, but it might also just be that the system has gone bad. The TAS was a very early attempt at digital reverb and not very good anyway. I'd just leave it out of the circuit and use the organ as you have it at present. You have set it up properly, according to your description.

                            Not sure why the pedals are in the Main amp, but it shouldn't really matter with a 301 if you have the same speakers on each channel. Perhaps someone reversed the cables right at the DAC output for some reason. You can reverse them and see if it makes any difference. As to the bass control not making any difference, are you listening to the lowest octave of a 16' or 32' stop? The bass control only affects the very lowest pitches of the pedal stops. The overall pedal volume is going to track the flute channel volume, since there is not actually a separate pedal audio system.

                            Good work. Glad you were able to get it figured out.
                            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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