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Rodgers 840

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  • Rodgers 840

    Hello All,
    I am a new user to the Organ forum, and I need some wisdom! I figure that some of you experienced organ techs might be able to help me.

    I am the recent recipient of a discarded Rodgers 840 (with MIDI pistons), which I’m told is in perfect working order. Unfortunately, in their haste to remove the organ from the church, the previous owner inexplicably cut two power cords. Both cords are inside the cabinet, on the bottom right as you remove the back of the cabinet, laying next to a big power supply.

    One of these cables is a standard two prong electrical plug, The other is a three prong grounded. It’s an easy enough job to put new plugs on the end of these cut cables, but I’m wondering what they are? I assume the three prong grounded is the main power to the organ, but where does the two prong cord plug in? Does it plug into something inside the organ, or should it also go into an external power outlet?

    Any assistance would be greatly appreciated!

  • #2

    Welcome to the Forum! To help us help you, is it possible for you to take a photo/photos of what you're describing and post here? From the photo, someone should be able to advise you of the options available to you for this organ. Congratulations on your acquisition!

    Way too many organs to list, but I do have 5 Allens:
    • MOS-2 Model 505-B / ADC-4300-DK / ADC-5400 / ADC-6000 (Symphony) / ADC-8000DKC
    • Lowrey Heritage (DSO-1)
    • 9 Pump Organs, 1 Pipe Organ & 6 Pianos


    • #3
      Be sure to follow the remaining stubs of the cut cords to see where they go. If they go inside a metal chassis of some kind, take photos or at least copy down the numbers and labels. That's a rather good late-80's analog Rodgers organ, pretty big one for a home too. Needs a total of six speaker cabinets, I think.
      *** 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
        The 3-wire cable goes to the main power supply. If you follow the stub of what is left, it should go to the power supply assembly (on a metal chassis), you'll probably find it has a standard IEC power plug at the power supply; if it does, just unplug the cable stub and replace the cable assembly with a standard IEC power cord. It might use a right angle power jack at the power supply end of the cable. This is probably cheaper than buying a 3-prong plug.

        If the 2-prong cable is just a cable lying in the console and not connected at one end, I suspect it was for something outside the console, perhaps a MIDI module. If it attaches to something inside the console, follow it and find out where it attaches. You may have to open the racks to find out. The racks have hold down screws at the top and bottom of the right side of each rack; the top ones attach to some aluminum sheet metal brackets. Often one is a swinging arm going from the middle rack to the inner and outer racks.You don't usually need to remove the swinging arm screws, just loosen them on all 3 racks so it can swing.

        If you want the technical drawings for this organ, send me a private message, providing you email address. Unfortunately, there is not a full tech manual on the 840, just the drawings. I can also provide the MIDI guide for Rodgers MIDI Phase II which is probably what you have.


        • #5
          Thanks for your replies, y'all! It appears that the 3-prong cord leads to the top of the power supply, and connects with a female end of itself, looks like it could be pulled out. The 2 prong leads into the left side of the amplifier, and looks like it is permanently wired in - no "removable" female end of the cord. My limited experience with Rodgers organs is that there is a single power cord. But this look like there were 2 coming out of the organ. Have you ever seen that before? I was wondering if there was some 2-prong receptacle inside the organ that it should be plugged into, rather than having 2 cords coming out and needing to be in 2 separate outlets. I have attached some photos if those make it clearer.


          • #6
            The 2-wire cord is going into an S102 single channel amplifier. The 840 normally has a 6 channel amp, powered by the main power supply to drive the main speakers. The extra amp might be for mixed down antiphonal speaker, supplemental pedal speaker, or for some unique purpose, like a speaker system for the choir to help them hear the organ better than through the main speakers. There should be a power socket on the main power supply where that speaker can plug in or, if you follow the black power cable adjacent to where the main power cable plugs into the power supply, it will likely lead to a power socket.

            If you follow the gray connector on the S102 amplifier, it is the input to the amp, and you can see what is providing the input to the amplifier. Its other end should connect to an output panel which will be labelled as to function..


            • #7
              toodles and JBird, thank you for the helpful info. Toodles, I will PM you for those tech specs, anything will be a help in the future.

              I have a couple more questions, if you don't mind! I will try to not flood y'all with too much at one time!

              I am putting 3 pics on, the first should be a board marked "WTC" - I am guessing that this is the Walker board that gives "jitter" to the sound?

              The second pic is the pre-amp board, which has the RCA plug spots for the reverb loop empty, maybe it was never added? or do these 2 RCA ports on a different board function as the reverb loop?

              Thanks again for the help!


              • #8
                As posted, the left picture is the output panel; the spots for the RCA jacks are not populated, and probably aren't connected to anything. The board was used on more than one model, and I suspect Rodgers never really used these spots (I've never seen them populated) and decided to hook up the reverb differently (see the right most photo). Note that the Channel 1 and Channel 5 speaker connectors are missing levers to release the wires. You push down on the lever to release the wire; if you pull up, the lever comes off, though it doesn't break.

                The middle photo is a Walker Technical Company board for "inharmonic chiff"; though I can't really say I know what that means in terms of sound, it would be to make the attack of the sound more like a pipe. If the organ has the jitter circuit installed (and there would probably be 2 or 3 of them if installed), they would be near the oscillator boards, probably on the back.

                The right most photo is of the output preamp. You've cropped to where the Reverb Loop is provided. This is where Rodgers did the reverb hookup using the 2 RCA jacks as shown. You can use the reverb out to drive an external digital rever (recommended) or a reverb spring (not recommended). The reverb in jack has a recovery preamp, and that might provide too much gain (and thus, distortion) and a frequency compensation circuit which it would be better to bypass if you use a digital reverb. The output preamp schematic will show you were to return the digital reverb signal if you wish to bypass the recovery preamp.


                • #9
                  Wow, thank you for the great info - I have much to learn and noodle around with! Have a good evening, all!


                  • #10
                    I looked at some old notes I have about the Walker board you pictured. The M-DAG stands for " Digital Activity Generator". Each of the 7 pots control how much activity (random sound???) is present in each of the (up to) seven audio channels. Most likely Swell Flutes, Swell Principals, Swell Reeds, Great Flutes and Great Principals. The slide switch on the board, turns all activity off or on (I think the switch is labeled as "kill"). This is to make tuning easier by stopping the generator output. This was information I found while repairing my Rodgers 760.
                    Also, the 760 had Walker DKA2 "Digital Keyed Air Sound" circuit modules. You might find them in your 840. They add air sound to the Principals and Flutes.


                    • quantum
                      quantum commented
                      Editing a comment
                      Do you have any more documentation on the Walker boards? I've also got them on my 760 but it has been difficult finding any details on what the pots control or any voicing procedures.

                    • hcmaestro
                      hcmaestro commented
                      Editing a comment
                      The M-DAG is putting a LOT of chiff on the great stops, it sounds like way too much to me.
                      I think I’ll try the kill switch and see if the sound is more pleasant. Are the pots supposed to be user adjustable? Maybe if there was about 50% less it would be palatable.

                    • jbird604
                      jbird604 commented
                      Editing a comment
                      The extreme chiff you hear might not be coming from the Walker boards. The regular Rodgers keying circuitry on these organs has both "air puff" (burst of white noise) and actual "chiff" (higher pitched transient) added to the basic pitches. This is adjustable, probably on the output preamp, with controls for "chiff" and "puff" or something like that, on a rank by rank basis.

                  • #11
                    I meant to also say in my previous post. I added an Alesis reverb to the 760, using the RCA jacks (as shown in your picture), and found the Rodgers would over drive the Alesis and cause hum. So I put a 100K ohm resistor in both the input and output leads going to the Alesis. It reduced the amount of reverb level but the hum was gone. I didn't experiment with different resistance values, so their might be a better value that gives more reverb.


                    • #12
                      No, I didn't find any documentation either. The information in my post came from Walker in Colorado. The MDAG had the factory paint marks on all the pots, so I never changed them from original. The DKA2 (three of them) in this organ had been added sometime later, not a factory install. Each pot has an etched label, so I guessed at what they would do. I found the "level", if turned up to high, would distort the organ voice. I finally turned the level down so the boards would stop adding the air sound. The 760 was a project organ with many problems to fix, and I decided the DKA2 added to the issues and left them turned off. It's possible the boards were bad? Anyway, the 760 has since been sold.


                      • #13
                        I have some documentation on the DKA keyers, but not on the DMAG boards. On the DKA boards, the air adjustment isn't to be adjusted unless the noise source (Q10) is changed; the others are adjusted by ear, but with the internal Rodgers air puff turned down.


                        • #14
                          Well, gents, thank you for the info. I replaced the severed power cable ends, and powered up the 840 (without the amp power plugged in). I plugged in a set of headphones, and everything seems to work fine. The chiff is WAY too much, like a theater organ, and the sound in the headphones is painfully dry, so I am thinking it needs a reverb. I noticed that plymouth53 mentioned an Alesis digital reverb, does anyone have a suggestion for a specific model that might be effective? I know Alesis is pretty well regarded by many.


                          • myorgan
                            myorgan commented
                            Editing a comment
                            The chiff is probably set to be played through speakers in a larger space than your headphones can supply (unless your head is hollow).

                            For the Alesis, I believe the Nanoverb is what most people use, due to price and functionality. Alternately, you could run the sound through a mixer with on-board effects (i.e. Behringer Xenyx 1204FX).


                          • Admin
                            Admin commented
                            Editing a comment
                            I've never heard chiff in a theatre organ. It's primarily found in baroque instruments. Theatre organs are characterized by deep tremulants. Are you conflating chiff and tremulants?

                        • #15
                          I've heard the slightest amount of chiff in my Allen MDS Theatre III tibias. I think most classical organists wouldn't even consider it chiff, and isn't really audible in normal playing--only careful listeneing on single notes when trying to hear the attack.


                          • Admin
                            Admin commented
                            Editing a comment
                            With trems off no doubt?