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How to use new speakers on a 1970's Rodgers 750?

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  • How to use new speakers on a 1970's Rodgers 750?

    I bought a 70's era Rodgers Scarsborough 750 recently. I bought it very inexpensively just to salvage the AGO pedals as I plan to MIDI them and use them together with some MIDI keyboards.

    Now that this organ is sitting in my garage (together with a dozen old speakers and a massive subwoofer) I'm tempted to just get it back up to speed and use it as-is. I'd be able to use the organ and pedals long before I start doing a MIDI conversion.



    I have two brand new JBL (powered) speakers I would like to use with the organ instead of the 30-40 year old Rodgers speakers. The JBLs receive 1/4" and XLR inputs. I took the back wall off the organ tonight thinking I might find a simple jack to plug the JBLs into, maybe needing just a simple jack converter, but no such luck.

    I found this:



    I'm guessing that the "flutes" are routed to the tweeters on the Rodgers speakers. The "pedal" is routed to the subwoofer. The "diapason" is the regular middle range speakers. And the "celeste" is maybe a special effect that gets its own speaker?

    So question:

    It looks like I'm going to need to run these four channels into a mixer and then send one audio-out to my JBL speakers. Any way of getting around that? Or is a mixer a necessity?

    Also, these jacks have five pins on them. Regular 1/4" has only two and XLR has three. What does a jack need five pins for? Is there such a thing as a cheap 5-pin to 1/4 inch or XLR adaptor?




    Thank you in advance to anyone who wants to help.

    -Neumie
    Last edited by Neumie; 01-18-2012, 11:20 PM.

  • #2
    The original audio system for that organ would have consisted of four S-100 amplifiers, each one feeding an appropriate speaker for the stops it carried.

    You are correct about the pedal stops going to the big woofer cabinet, but the other three channels all went to standard full-range cabinets. In some installations there were different varieties of speakers for different channels, but all are basically full-range regardless of which stop family is being carried.

    For a simple hookup you could certainly mix all four channels down to one. Not a great idea for a permanent setup and the tone would be compromised somewhat, but you could play it and get some use out of it.

    Behind each of these four 5-pin output jacks you'll see some wiring. You'll see that pins 2 and 3 on each one carry the 12 volts that was used to turn the remote amplifier on (each S-100 amp has a relay inside that powers up the amp whenever the organ is powered up). You can ignore those pins since you'll be using non-Rodgers amps.

    Pin 4 has nothing at all connected to it. The other two pins -- 1 and 5 -- are the ones you are concerned with for getting the audio out of the organ. Pin 1 is the ground or common for the audio, and pin 5 carries the actual audio signal.

    So, if you want to convert this to a regular 1/4" output jack, connect pin 5 of the Rodgers jack to the tip of your 1/4" and connect pin 1 to the shield or ring of the 1/4". Run all four into a mixer (or run each one into its own powered speaker if you have them) and adjust the levels as needed. You should find something very close to standard line level outputs.

    If you look at the pre-amp board of the organ you'll see some mixing switches. Not sure just which ones you'll see, but you could see a way to mix all the channels down into one (or possibly two) right on the organ's own pre-amp.

    Good luck!
    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
      Holy cow, John ... articulate, straight to the point, ...

      thanks for the tutorial and taking time to reply!

      1) In your advice, you numbered the pins on the five pin jack. How do I know what pin you are referring to when you say "2" or "3"...?

      2) You said mixing down the four channels would compromise the tone and would not be ideal for a permanent setup. So, ideally, (assuming this is going into a normal living room, not a church), you might suggest three full-range speakers and a subwoofer? Four speakers for four channels?

      3) I saw what I think are the two switches on the back wall of electronics in the organ. Perhaps you can tell me what mixing down all the channels right inside the organ might look like? Right-up, right-down, etc. And then where would this one mixed-down signal come out? Any one of the four 5-pin jacks?

      Thank you again for the reply, John! You're really helping me out and I think this is the information I need to get this Rodgers going again.

      -N
      Last edited by Neumie; 01-19-2012, 12:06 PM.

      Comment


      • #4
        I believe that your instrument is a Scarborough 750 which is a variant of the 700 series.
        You can get a users manual at lds.org/cm/pdf/OrganManual_Rodgers_Model_700_eng.
        As your picture shows there are four output channels.
        The usual MINIMUM is two, flute and diapason.
        A woofer is added for the Pedal to make three.
        The fourth adds the Swell/Celestes.
        I have the model that precedes yours and trust me, to get the Swell Strings and Reeds as well as the celestes to
        function properly, that is to have the two ranks as it were, coming from separate souces, to have audio beating, is the way to go.
        EVERY DAY IS SATURDAY!
        ROLAND CLASSIC C-330 IN MY LIVING ROOM

        Comment


        • #5
          The Rodgers 750 has two tremulants. One affects the entire organ, and the other affects only the Flutes, and is in place of a LESLIE output socket, which you do not have. It will function only when the tab for full flute trem is on.

          The 5 pin plugs are "5 PIN AMPHENOL".
          When you look at the pin side of the plug, you will see a raised dot on the periphery and numbers 1 to 5 adjacent to the pins.
          Hope this helps
          EVERY DAY IS SATURDAY!
          ROLAND CLASSIC C-330 IN MY LIVING ROOM

          Comment


          • #6
            Originally posted by rodgers110 View Post
            I believe that your instrument is a Scarborough 750 which is a variant of the 700 series. I have the model that precedes yours and trust me, to get the Swell Strings and Reeds as well as the celestes to function properly, that is to have the two ranks as it were, coming from separate souces, to have audio beating, is the way to go.
            Thanks for the reply, Rodgers110. I'm new to organ terminology. When you say that the way to go is to have the two ranks coming from separate sources, does that mean I'm good with using two external speakers? Or are you pressing the case to have three speakers and a subwoofer?

            I'm planning to use two high quality JBL 15" speakers that have tweeters in them as well. I imagine everything from bass to the high end should resound clearly.

            I'm just wondering if two speakers is enough to get that separation you are referring to. Or are you saying a person needs all four channels?

            -N
            Last edited by Neumie; 01-19-2012, 02:13 PM.

            Comment


            • #7
              I would find a way, to make room to utilize 4 output channels. Two channels will obviously work, but you are relying on the time share concept to give you the separation and accoustic mixing. There are 2 sets of oscillators inside, the unit rank and the celeste rank. The flute celeste stop utilizes the flute channel for the unison portion and the diapason channel for the non-unison portion. Similarly, the String celeste uses the Swell channel for the unison portion, and the diapason channel for the non-unison portion.
              The PEDAL needs a W6.
              The SWELL having its own M13 gives the REEDS, STRINGS, and Celestes more user control.
              The users manual usually has a section on the technical description of the organ. Understanding this is the key to what you decide. Try both 2 channel and 4 channel and then decide.
              EVERY DAY IS SATURDAY!
              ROLAND CLASSIC C-330 IN MY LIVING ROOM

              Comment


              • #8
                THANK YOU for the great help and advice. I'm so close to having this thing up and running.

                I wonder if anyone might look at these two photos and answer a couple of last questions?






                1) I believe those two switches are to "mix down" the four channels into a lesser number. Can anyone tell me what the two switch positions will do? ie, What does left-up, right-up, left-down, right-up, etc do?

                2) And if I adjust these switches for two channels to correspond to my two speakers, which of the four 5-pin jacks would be in use?


                -N
                Last edited by Neumie; 01-20-2012, 03:31 PM.

                Comment


                • #9
                  Push both switches up (in the direction of the arrows) and your four channels will be mixed down to just two. Connect one amp and speaker to the flute output and one amp and speaker to the diapason output. Both speakers need to be full-range because each channel will carry a wide variety of frequencies. This will give you a pretty decent organ sound, not as big and spread-out as with all four channels, but it should be quite enjoyable. Post your results here!
                  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


                  • #10
                    Hi John,

                    Thank you again. I can't believe what a resource you've been.

                    I still need to solder up the 5-pins per your instructions to hook up my JBLs this weekend, so I still haven't heard a peep out of my organ yet, but the lights did come on ... so something's working. The headphone jack was removed for some reason, so there's no testing the organ that way.

                    When I opened the back of the organ a few minutes ago and pulled away the wall of electronics, I found the power supply with two more jacks marked "Channel A" and "Channel B". Does this organ have two sets of speaker routings already wired? One for four channels on the back wall and one for two channels on the power supply?

                    Can I plug my two JBLs into these two jacks? Or is this something different entirely?

                    -N




                    Last edited by Neumie; 01-20-2012, 08:16 PM.

                    Comment


                    • #11
                      Not sure. I've seen that series Rodgers set up in a number of ways. It's possible that it once had internal speakers and the power supply chassis you're looking at actually contains a two-channel amplifier, a fairly low-power amp that would have been used to drive internal speakers.

                      I wouldn't advise taking the audio out from those two jacks, though, as they are further down the signal path than those on the rear panel. Your best bet is to solder some standard audio cables onto pins 5 and 1 of the flute and diapason outputs and take that into your JBL powered speakers.
                      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


                      • #12
                        Got it, John. Thanks. I'll probably be posting again as I plan to spend the weekend working on this.

                        By the way, I found a promotional flyer for my Scarborough 750 and it said that there was an optional two-channel internal speaker system, which my particular organ did not have. It's strange though that Rodgers would have put in the more expensive power supply with the jacks on it, even if the customer didn't opt for the built-in speakers. But I think regardless, you figured out what the two jacks were for.

                        I really appreciate your help. Please check back as often as you care to ... your help is invaluable to me.

                        Have a nice weekend.

                        -N

                        Comment


                        • #13
                          I got as far a soldering up a 5-pin to a 1/4-inch jack and plugging it into a JBL speaker. I flipped up both "mixer" switches on the preamp board so I seem to be running a two channel organ right now. I played the keys and - holy smokes! - I've got sound. Both the flute and the diaposon output channels gave me sound. So sweet. Very happy. The 750 is in fact functional.

                          Now, I worked each key up and down the keyboard and something is not right under some of the keys. (Please excuse the rough description as I don't know any real organ terminology. I've lived with synths all my life and real organs are new to me.) Organ registrations obviously have multiple levels of sounds that are being played. On a Hammond, I think in terms of pulling out more drawbars to add more harmonic levels.

                          Some of the keys on this organ are not playing all the different levels of tones. One key has a nice fat bass sound and a couple of other tones above it. The neighboring key will have only the higher tones, but not the bass. The next key will have the whole shebang again.

                          If this was a Hammond, I would know it needs a busbar job. The contacts under the keys of old Hammonds (there are several of them for each key) get dirty and sometimes not all the contacts are connecting. Hence the partial registration, with some levels missing.

                          Is that the same thing with my Rodgers? Dirty contacts?

                          I did find one loose electronic chip lying about in the back of the organ ... I have no idea where it goes as it's pretty small ... so I don't know where to look for a hardware problem versus just getting the full registration equally out of every key.

                          I'm sure this is a common problem. Can anyone tell me what's going on? Is it a home-fix?

                          -N

                          Comment


                          • #14
                            Not contacts as in a Hammond because a Rodgers has only one contact under each key. The multiple tones are drawn together by the various keying boards. If you get anything at all from a key then the contact under it is working.

                            Now, some organ stops do not run the full compass of the keyboard, or may break back at certain points, which would cause tonal changes from key to key. For example, celeste stops often do not play at all in the bottom octave or the top octave. Mixture stops change composition numerous times across the 61-key range. Mutations (fractional stops) and 2' stops may "break back" at some point in the treble. Chimes and harp (if you have them) may only play in a limited range, perhaps two octaves.

                            However, you could very well have some missing notes in some of your ranks. The only way to determine this is to put on each stop individually and play all 61 keys (or 32 keys of the pedals) to see if each stop plays as it should.

                            Best place to start is with the Principal or Diapason 8 on the Great. Be sure that you have all pre-sets canceled, crescendo pedal closed (if this model has one), tutti canceled if there is one. Just the one stop sounding by itself. Now play each key of the Great manual and make note if there are any that do not sound. Next try the Octave 4, then the Superoctave (or Fifteenth) 2. If all keys sound on these 3 stops you have just proven that the Unit Diapason rank is OK.

                            Now go through this same procedure with the 8, 4, and 2 foot flute stops in the great division. If all these keys play you will have tested the entire unit flute rank. Now test the reed stops in the swell in the same manner. Next the Viola Pomposa. Then test each 16' stop in the pedals. By this point, you'll have a pretty good idea of what is working and what is not.

                            If you only have a note or two dead, and you are only playing for casual enjoyment you may not care. Putting on several stops together may almost completely mask the missing notes. But if you intend to do serious playing you will probably want to get this fixed at some point.

                            Unfortunately, there isn't much you can do without calling in a tech unless you just want to very carefully clean up the inside of the console, inspect the wiring everywhere, and check all those little overlapping circuit boards in the upper left (as you look at the console from the back). Those little boards are the tie points for all notes of all stops and sometimes you'll find a loose wire or maybe two boards touching. There should be card or paper insulators between the little boards, but maybe some have fallen out. You do need to make sure the boards don't touch each other when the back is put on the organ or when the rolltop is pushed in.

                            You could tune the whole thing if you want to. There are very inexpensive (or even free) apps for iPhone or Android that work as well as an expensive digital tuner. You need a fundamental understanding of the concept of tuning though, and you don't want to damage the Rodgers oscillator coils by turning the wrong portion (only the metal cap of each coil is movable). You may find the lowest bass to be seriously out of tune because the pot-tuned notes are much less stable than the coil-tuned ones.

                            The thumbwheel pots on the pre-amp are for leveling the various ranks, channels, and some individual stops. You need some knowledge of voicing theory to set them perfectly, but it won't hurt to tinker with them and see what happens.

                            Have fun!
                            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


                            • #15
                              Oh my gosh, John. You're a lifesaver. So many helpful insights. Thank you for the tutorial about how to check for missing notes in the ranks. I'm on it.

                              Okay, I heard you about getting a tech to come visit. (Are you in California anytime soon?) As far as I know, Sacramento has only one organ tech ... I'm going to give him a call this morning and set up a visit. I had hoped to do this all myself, but I can't imagine he would be that expensive.

                              Thank you again for all the help. It was quite a thrill last night to get even one 15" JBL hooked up and hear the organ play. I'm really looking forward to the whole setup.

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