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  • Project Praeludium begins

    Thank you all for your help in deciding to get the Praeludium. $300 for the instrument and $170 for truck rental and gasoline and it is nestled safely in my garage for freshening and modification for VPO project.

    I think it is a Praeludium (not a II) but the experts can chime in. The left hand patch panel has aux in (wonder what that is for), Left and Right out (line level I presume, Phones, master (volume?), trem speed, trem depth, and another level control with a three letter abbreviation that I can't recall or quite read in the picture. The right hand panel has keyboard switch, pitch, Ensemble B-A (what does that one do?), Chiff B-A (dittos, what does that do), and MIDI

    mike









    Attached Files
    If it is Caesar that you worship, then Caesar you shall serve.

  • #2
    And some gut shots.



    It looks like the stop rail and circuits boards might be able to be disconnected and repositioned almost horizontally so that a third keyboard could be added if the brass plates on each end are removed and a mounting setup fabricated to lay it out more flat. This would probably be easier than working out a way to add the keyboard underneath. However the way it is designed I think that the existing stack could be lowered a tiny bit if needed to make some more room.



    What do you suppose this little black box on the left side is??? Output and input for left and right and defeat are how the jacks are labeled.



    Not likin' the way that left most card is bent but a little afeared to awake a sleeping dog by messing with it.




    Looks like if there is any hope of adding a third expression shoe I will have to move the toe studs and associated PCBs over by several inches. Looks doable but would need to be handled with care. Might need a real wood crafter to help me. The jacks above the expression pedals are labeled as outputs (I presume speaker level outputs) and the right two say something about remote???

    mike
    Attached Files
    If it is Caesar that you worship, then Caesar you shall serve.

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    • #3
      That's definitely a Praeludium II, although a very early one. I had one with warping in the phenolic circuit boards, but it still worked. I have some worries with yours because the warped board is the CPU board, and any failure there is likely to take the whole organ down. Later versions had green glass boards which avoided this issue. The black box looks to be an Alesis Nanoverb that was added to replace the awful stock spring reverb that would have been present in this early model.

      The output board on the back has two unbalanced line level outputs for connecting to an external amplifier. The Remote jacks furnish +12 volts to drive a relay for switching power on and off to the amplifiers. All the amps we used to sell with these could be switched by the organ.
      Last edited by michaelhoddy; 03-28-2013, 09:30 PM.

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      • #4
        Cool thanks. It looks like only one channel connected to the black box. The remote is nice. I suspect that one could figure out a way to trigger a power sequencer to start the amps, interfaces, computer etc. Would the capture battery be on the CPU board? What would you do about the warped board if anything?

        mike
        If it is Caesar that you worship, then Caesar you shall serve.

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        • #5
          It is identical to the full-color photo that came with the Praeludium II schematic set I have here in front of me.

          I would try to find one of those green glass CPU boards; in my experience, the one in your new baby isn't going to heal itself.

          I believe yours is an early II, because the later versions were marketed by Galanti Organ Builders, a warehouse operation in Lake Oswego, Oregon. That's right down the street and around the corner from Rodgers, and was headed up by a former ROC salesman. (As you may know, GEM in Illinois is short for Galanti Electro Musical.)

          Let me know on the manual.

          . . . Jan

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          • #6
            Thanks Jan, PM sent. I dashed off this thread in the middle of the night as I was so excited but I left out some details. So far I have found a burned out stop tab light and about 1/2 dozen of the pedals have a loud clatter when released. I will have to get inside to see if it is a missing pad (felt?) or the spring problem. One thing that concerns me is the ability of the pedals (or the back cover under the bench) to handle being stood on. I might have to make something to put over the rear part to keep the particle board from getting broken by such abuse.

            I haven't used every stop or piston yet but so far have not noticed anything else that is currently not working. So far it seems at least "not bad" for the price.

            mike
            If it is Caesar that you worship, then Caesar you shall serve.

            Comment


            • #7
              Glad you got the organ. Some previous owner must have baked this instrument in a sunny window or a cheap storage unit in Texas! Hope you'll be able to work around the warping. I got the new cable onto the pedalboard of the Italian Wurlitzer on Wednesday and heard every note on the pedalboard play. But after wrapping up, I got a callback that several pedals had stopped playing. Have directions from Viscount's tech to give the contacts a good cleaning with Deoxit. So you might want to go over yours with Deoxit at set-up for best performance. Regards!

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              • #8
                Thanks for the tip OR4M. Is the access to the contacts/springs through the top panel at the front end? Remove screws and lift off?

                mike
                If it is Caesar that you worship, then Caesar you shall serve.

                Comment


                • #9
                  That's exactly like the PII at my church, down to the brown circuit boards in the rack. The battery is still on your CPU board, so you will want to move that little puppy ASAP and hope it hasn't leaked and damaged the socket yet. (It's the teal-colored item near the bottom of the CPU board, just above the socket.) I got a 3-cell re-chargeable battery at Walmart in the phone section -- the kind of battery pack that goes into the handset of a cordless home phone. The pack is shrink-wrapped for safety and has a couple inches of wire leads, so it leans up against the board where it can't do any harm.

                  The reverb signal is mixed down to a single channel in this model, so that's why your nano-verb has only one input and output cable. That's the way it has to be. The reverberated sound is mixed back into both channels by the mixer board in the organ.

                  Your clattering pedals are typical. Take off the metal cover and have a look at the mechanism to see why. Mine at church has had the pedals lashed to the shutters with strips of cloth! They don't clatter any more, so I guess it was a good solution, but it wasn't me who did it. The switches are glass reed type, not serviceable in any way, so there is no cleaning them. If they malfunction they have to be replaced. But the biggest problem with the pedal switches involves the springs that hold the little "shutters" in place, and that is why a previous tech tied mine up with cloth strips.

                  The P.N.C. is "pipe noise control" and lets you blend in some white noise into the audio. The noise is gated by the CPU and sounds like a little burst of air with each key press. You may like it or not.

                  The Ensemble A/B switch produces more or less tuning difference between the stops and divisions. Chiff A/B gives different degrees of chiff. You already know about the keyboard inversion switch. The Aux input is a STEREO 1/4" jack, so if you want to run an external device into the organ audio, get a stereo plug. BTW, audio inserted via this jack will not be affected by the expression pedal or the volume sliders, just goes straight into the power amp.

                  The 1/4" output jacks on the back are simply wired in parallel with the RCA-type output jacks on the front, both of them delivering line-level output which can drive any typical external power amp.

                  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

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                  • #10
                    Mike, on the Wurly both the back and top of the switchbox are glued together. Three screws in each. Then it lifts up. I hadn't inspected the Wurly for the battery. I'll have to keep that in mind for a future update. Glad to know a phone battery will work.

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                    • #11
                      Hmm... That white area on the bottom of the battery looks evil...



                      Do I need to get a ground strap (wrist strap) before pulling the board to replace the battery? Where would I get one of the improved PCB? Cost? How about replacing the battery on the existing board... is that warp too bad to continue using that board?

                      mike
                      Attached Files
                      If it is Caesar that you worship, then Caesar you shall serve.

                      Comment


                      • #12
                        Yep, that battery is at the point of causing serious trouble, so get that thing off ASAP. Last time I tried, I could not locate a new CPU board for one of these, and I searched all over the place. Some of the boards are still available from GEM, but not the CPU board, AFAIK. So, you need to rescue it. The warp probably isn't going to keep it from working. Worst case, if some of the traces in the area of the warp get broken, you can solder wire jumpers over the cracks.

                        I never worry too much about static discharge when handling these boards, as they are not all that sensitive, as more modern boards are. Just be sure to discharge your hand onto the metal chassis or some earth ground before removing the board from the socket. BTW, it may take some tugging to get it out of the socket, and you must simultaneously release the two plastic clips holding the board down, one at each edge. After you take it out, clean the edge connector gently with a paper towel moistened in WD-40, wipe dry, coat the edge connector with Vaseline and wipe off almost every bit of it before re-inserting. Makes re-insertion easy and staves off future corrosion.

                        As to the battery, unsolder it from the board and take note of which end is the + end. Get a 3.6 volt rechargeable from Walmart and solder the leads to where you removed the battery pins. If the battery leaked and damaged the board or the socket, do whatever it takes to get the battery juice all cleaned up, and repair any traces. Severe damage might require soldering on a wire to the CPU board and jumping to whatever point on the motherboard the contact should have gone to. (You're not likely to need to do that, since the organ still plays.)

                        The stop lamps are available from Rodgers, as the same lamps were used in their Italian-made imported models. I don't know otherwise where to get them. They are peculiar, look just like little fuses, probably were once used in automotive dash boards but seem to be hard to find in the US. The front face of the stop tabs pull off, revealing the lamp inside in a holder like a fuse, just pry them 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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                        • #13
                          I did a Google search on "fuse-type lamps" and got several links. They seem to be readily available in 6v, 8v, and 12v ratings, and there may be others. (Since I don't need any, I didn't follow more than 1 link.)

                          David

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                          • #14
                            Thanks for the tips John and David.

                            That looks to be the same battery type that took out my Korg Poly-Six. I began the repair on that one but never finished as it required repairing traces (which I did) and replacing a logic IC. I think I have some of the required ICs from an old organ tone generator board but since I didn't really need the Korg it kind of fell between the cracks. The suggest repair on that one was to replace with lithium battery (2032 IIRC) and disabling the charging circuit but the phone battery idea sounds much better.

                            Does the phone battery have to be Ni-Cad or is the modern replacement type (NiMH?) OK as well? I presume the red lead goes to the Pos end of that battery. That Vaseline idea is clever and cheaper than Fader Lube.

                            I was thinking about that aux in and am wondering if it just feeds the internal power amps or if it also shows up on the line level outputs. It would be more useful of course if it went to the outputs as well but even if it just goes to the power amps I think it will be useful during testing of the midi modifications and such as I can just patch the headphone output of the VPO computer in there and not have to set up a complete amplification system. Of course when we get the multi-channel output and everything set up for the actual installation the internals will not be of any use.

                            Well on second thought it might be useful to use the built in amps to power the remote speakers for the internal voices to save buying an additional stereo amplifier but I would have to rig up my own output jacks (no big deal). Once the internal speakers are no longer needed I am considering removing them and building enclosures for them for use in 4' and mixture channels. I presume that the metal cylinders enclose some sort of mid tweeter. I am not sure the 10" mid-woofs have enough uumph for 8' at auditorium filling levels but should be fine for 4' and above me thinks. I think that the remote speakers for the internal voices should be quite a bit heftier especially since 16' pedal stops are involved.

                            Anyone ever have the stop rail off of one of these? Is it as easy as it appears (screws on the brass plates at each end and watch for the hard wired leads)?

                            mike
                            If it is Caesar that you worship, then Caesar you shall serve.

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                            • #15
                              BTW, just a quick question. Is it OK to remove that battery and continue to play without it until I get a replacement.

                              mike
                              If it is Caesar that you worship, then Caesar you shall serve.

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