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Connection of Rodgers 800/900 PSU and 6 channel amp questions

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  • Connection of Rodgers 800/900 PSU and 6 channel amp questions

    Admin: just noted I posted this in the wrong forum. Please move to elecronic organ repair. Thank you.

    Hoping the resident experts may he able to assist me. I have acquired a model 800/900 power supply unit, power transformer and 6 channel amp from a Rodger instrument that was parted, all stated to be in woorking condition. The transformer has two twelve pin molex plugs that go to corresponding connectors on the aluminum housing of the PSU. the amp has two 4 pin molex plugs that plug into the power supply, but there are three 4 pin connectors on the power supply, so not sure which two are the power supply to the amps.

    Finally, there is a 15 pin molex on the power supply circuit board that obviously was for the harness into the console (power switch, indicator, relay control line etc.). The plug is still on that one, with about an inch of harness (rest was cut off).

    does anyone here have access to a pinout/connection diagram for this setup? I'm planning to use it to upgrade a Rodgers 750BE console with expanded audio. Can post pictures here later if that would be helpful. Any insight would be greatly appreciated.
    Last edited by KDirk; 03-21-2019, 03:09 PM.

  • #2
    It would be very helpful to know the model number of the organ that originally had your power supply.


    • #3
      I realize that, but unfortunately that information wasn't provided to me. I erroneously assumed that the connections would be mostly self-evident. I'm going to say that it was a 800-900 series from around 1979 to 1982 or 83, as it has that late 70's to early 80's style Rodgers logo (Same as on my 750BE from 1981) on the power supply chassis.

      It is marked model "800/900 power supply". It bears a strong resemblance to the type 19 power supply used in a 925, but that is a later revision as it has the slightly newer Rodgers logo (not the fancy script style, but the one with the D and G overlapping) and a socket for the line cord, rather than hard wired. Also has a two prong ungrounded service outlet. Hopefully that helps narrow down the time frame and range of models somewhat. It does have a relay bypass toggle.

      it would have been a large instrument with 6 channel (amp mounted on large aluminum. acker, with 2 NEC 4 leg transistors per channel), sound standard and a large lighted capture action given the number of outputs on the power supply designated for stop lamps. Likely a 900A/B or some such in that same range of models. I am awaiting a response from the individual I purchase them from, and if I can get a specific (organ) model number I'll add it here. Hopefully this post will get moved soon so that it is in the correct subforum.


      • #4
        Originally posted by KDirk View Post
        just noted I posted this in the wrong forum. Please move to elecronic organ repair. Thank you.
        So moved.

        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)
        • 11 Pump Organs, 1 Pipe Organ & 7 Pianos


        • #5
          Is there a part number on the printed circuit board? That might help. Could be on the front in silk screen letters, and also is probably etched on the circuit side.


          • #6
            Ok, the power supply circuit board has the ID 6112-767-17 / ROC 2767B. The chassis (aluminum shell) is marked TYPE PS 800/900 6551-181 / 4351-181. The amp circuit boards (there are two identical mounted to one backing plate, 3 channels each for 6 total) are marked 6112-770 / ROC 2770B. Still waiting to hear from the individual I purchased these from as to the organ model they were removed from.

            The power supply has three four pin molex marked SP-1, SP-2 and SP-4. The two twleve pin molex on the chassis (where the transformer connects) are marked SP-1 and SP-2. The 15 pin on the circuit board is marked SP-5 with the following wires (all cutoff):

            1 - white / yellow stripe
            2 - white / red stripe
            3 - white / green stripe
            4 - grey
            5 NC (no connection)
            6 - violet
            7 - red
            8 NC
            9 NC
            10 - orange
            11 - brown
            12 - white / violet stripe
            13, 14, 15 NC


            • #7
              Here is the diagram for the power amp: 6112-770 Amplifier.pdf

              I'm still looking through my manuals to see if I can identify the power supply--I get close but not quite there.


              • #8
                I found that power supply. Looks like it was used in the Models 820 and 900. Documentation is here:
                Schematic Power Supply.pdf
                Attached Files


                • #9
                  Photo Power Supply-compressed.pdf


                  • #10
                    Thank you for that, it saves me a ton of work doing voltage checks trying to determine what went where. I suppose I'll need to utilize the relay bypass function as it appears the PSU looks for a signal from the CPU - which of course won't be present in my application on the 750BE which is a basic CMOS time sharing system with no CPU proper, and certainly not the one being looked for. Unless I can determine the nature of that signal and replicate it, I'll have to wire up a relay controlled 110V outlet switched by the power switch on the organ.

                    After 4 years of collecting parts, I may finally be able start my console upgrade. The organ works nicely as is, but there are a number of things I really wanted (drawknobs versus tabs, better audio, an additional manual). Going to be a lot of wiring in my future by the looks of it.


                    • #11
                      The power supply uses a "keep alive" circuit--pulses from the CPU that regularly reset a power-off circuit; the bypass and standard power switch are likely easier to use and less troublesome. The keep alive approach uses momentary action switch to short around relay contacts that self-energize. More trouble than it is worth, if you ask me.

                      Most Rodgers from this era use lighted drawknobs, and if you ask me, though they look nice, they are not nearly as easy to use as stop tabs, especially when, like in your 750BE, the tabs are in 2 rows centered about the manuals. It makes all the tabs really easy to reach. The lighted drawknobs do not work as smoothly as mechanical drawknobs--they are, to me, stiff to operate. When you think about it, the drawknob has to be held in neutral position by 2 spring forces, so they can't really be light.

                      Your 750 console could fit a 3rd keyboard--certainly there is enough height. Send me a PM if you want to try--I've got some old Rodgers organs that I will be parting out. If you ever wanted to make a trip to Utah, I can load you up! A visit to Salt Lake City might be worth it for a Tabernacle Concert.


                      • #12
                        Toodles, I really appreciate the information and feedback. I may be interested in some parts if you are dismantling some instruments, will PM you for details with what I may still be looking for.

                        As to the power supply, thanks for the explanation. I sort of figured that was the principal of operation with the relay, and know the later model consoles (than my 750BE) had momentary action power buttons rather than the latching key switch. I intend to keep the key switch, or may opt for a nice latching pushbutton if I feel the need for an update.

                        While I understand the operational ease of the tabs and their layout, drawknobs are just a personal preference of mine; the first instrument I played was a drawknob console and that probably set my expectations going forward. I will be retaining some tabs, probably a single row for inter-divisonal couplers and special functions. I managed to come into 60 Syndyne moving drawknob units (some NOS, others parted from factory prototypes, courtesy of Matt Neill in OR) at a price that made it -almost- practical, so I jumped on them.

                        I also picked up a pair of Rodgers side jamb boards in walnut (matches my console finish) from an old 330 with lighted drawknobs still installed. I've removed them from the jambs and plan to try and sell them. I also have some old (late 60's era or very early 70's) moving drawknobs - early Syndyne deisgn I think - from a 990 that I picked up a long while back, but they are far to deep behind the jamb board to retrofit to the narrower 750BE console width. They are also short-throw, 3/8' travel unlike the newer ones. So, I'll be trying to sell.them as well.

                        I know a drawknob/tab (rather than rocker rail) combo is uncovnentional but I'm not buying a bunch of rocker SAMS just to get that AGO standard look. At this point, I could actually go four manuals, as I have 2 additional Loduca keyboards with matching cheek blocks. Or, in could put in a stack of 3 Laukhauff wood core keyboards from the aformetioned 330, though honestly I have found I like the lighter touch of the Loduca keyboards. So, may well sell the Laukhauffs once the plan is finalized.

                        I do have additional ranks of oscillators, keyer/formant, preamp boards, and diode slides and back planes so could (if I have the ambition) wire up additional stock tone generation. I think the Rodgers analog system sounds great with enough tweaks (digital multi channel reverb is a must) and my 750BE has some Walker enhancements installed. Apparently, it was used periodically by the local dealer years ago as a field demonstrator unit at the church where it was originally located. Have two utility finish Credenza speaker cabinets as well, so was already a nice setup.

                        I may reuse the stock capture action (have a second set of boards for that so can tie in additional division in parallel to the existing pistons) it also have a Peterson Duo-Set with enough boards to support 6 divisions at four memory levels. I'd love to go all out, but the amount of added work to do four manuals and a complete change of the capture action is beyond what I had planned, even though it would give me an instrument well beyond anything I'd ever hoped for. MIDI capabilities are planned for as well, but will probably be a long time before I can afford a Hauptwerk setup to make that worthwhile.

                        Anyway, acquisition of parts is nearly done so it will be time to start the real work. I have some details and design decisions to finalize before wood can be cut and wires run, but it's getting close.


                        • #13
                          I think that Allen does, and Rodgers did (at one time) use standard SAM units for rocker tabs, and dealt with the difference in neutral angle with an angle bracket of some sort--might be an option for making rocker tabs using the regular SAMs.

                          Definitely send me a PM--I know have some stuff you can use that might otherwise go in the dump. At least I have some engraved stop tabs/drawknob heads that ought to work for your project.


                          • #14
                            The rocker tab SAMS (Syndyne supplied) on the 750BE have the metal mount bent at the angle the tab rests, where rocker SAMS typically are straight (at a 90° angle) to the mounting angle. I suppose if I wanted to do the extra work, i could disassemble the SAMS and straighten the metal mount on the armature to use vertical rockers, but that's not really worth the effort. I'll just stick with tabs, they work well enough for what I'll need to do.

                            Plan is to have speaking stops and intra-division coupler on drawknobs, inter-divisional couplers, special functions like antiphonal controls, MIDI and perhaps a few other oddball things I'm planning on doing on the tab rail. As it is, I'll have to increase the height of the console and lengthen the rolltop (I have a second matching rolltop on hand I can scavenge tambors from) to accomodate the side jamb height.

                            This will also add clearance under the flip-top to mount the Peterson Duo-Set action if I end up using it. That's another can of worms though, as the stop and piston common polarity is negative. Rodgers uses positive common, so would need inverters on the inputs, and the Peterson action doesn't support lighted pistons so I'd either lose that functionality or have to provide an alternate means of latching/driving the piston lamps.

                            It's going to be a big project, but will end up with an instrument that is far beyond what I had ever expected to have at home, and nicer than many instruments located in a church.


                            • #15
                              You don't need to bend the armature angle--you just need a wedge shaped piece or a V-bracket (rather than L-bracket) to make up the angular difference.