Rodgers question/s (750BE and 780)

[kiaya611]

Hello,
I recently got 2 Rodgers Organs. The 780 (Asilomar) and 750BE (Scarborough). One question is easy and that is does anyone have pictures/specs for the Rodgers P16 speaker (or even just if it uses 2- 12" speakers as I believe the P32 uses 2 15" speaker in a larger enclosure. The second question is more involved. Would it be possible to take the 32' stop from the 780 and add it to the 750BE? I know that it is much more than moving/adding a tab. I am just wondering if doing that kind of modification is done or if it is so involved that people just don't do it.

If I could, since the 780 was a very limited run instrument and used some new/odd technologies and the 750BE is a more traditional design, using established Rodgers keying, wiring, etc. Also, if anyone has originals (or even good copies of both instruments' users and service manuals, please PM me if it would be possible to either get a copy or if you were interested in selling one (or more).

Has anyone tried to take 2 models that are similar and effectively make a larger speced organ using parts from both? They each have features and some stops that are different (i.e. the 32' on the pedal of the 780. That would be very nice to have on the 750BE. I having found information on the 780 yet. From what I have gathered, they only made 40 of them and when they were built, there were changes going on at Rodgers, so it was the last model using some of the internals as well as some (for lack of a better word), "experimental" technologies like the keying system that it uses.

Thank you,

Steven

[toodles]

First, I would strongly discourage you from trying to move the Contra Bourdon from the 780 to the 750B. The 780 is a far more complete organ than the 750B. The 780 having these stops over the 750:

Pedal
32’ Contra Bourdon

Swell
8’ Gamba
16’ Vox Humana
8’ Post Horn
8’ Vox Humana
Glockenspiel (if it hasn’t been separated from the console)
Swell Alternate Mixture

Great
2-2/3 Quint
8’ Harmonic Trumpet (from Swell)
8’ Vox Humana (from Swell)
16’ Piano/Harpsichord (available on Pedal if you elect to do so)
8’ Piano/Harpsichord
Great Alternate Mixture

The only two stops the 750 has that are not on the 780 are a 1-1/3 ft. and Cymbel II in the Great. I think you’ll find the Great Alternate Mixture is a suitable substitute for the Cymbel II. All the other stops are the same, though they have names that match the theatre organ style. In addition the 780 has 61-note celestes whereas the 750 is just 37 notes—the middle 3 octaves.

In addition, the 780 has a console that will fit through a 30 inch doorway and that can be very valuable. It has a more complete combination action, and many useful programmable features.

The 780 is part of the LTG (Linear Tone Generator) series of Rodgers organs, and it does not have any technology that is "experimental"--everything it has is used in other organs of that series: the 100 Series Organette, 650 York, 705 Kent, 740 Glasgow, 745 Concord, 755 Concord, 760 Concord, 770 Exeter, and 840 Windsor; the 650, 705, and 740 even have A & B version models. The technology was used from about 1983 to the end of the decade. Other organs used the same technology, too, but didn’t use the LED stop tabs. The 780 is only unusual in that it was specified as a hybrid theatre/classical model, so the stop names and voicing adjustments mostly are voiced to sound like a theatre organ. It also has color coded tabs—but you can adjust the voicing so it sounds just like a classical organ of that series. The 780 was one of the early models of this group, so its design dates from around 1983.

To accomplish this change, you’d have to remove the 32 ft octave of oscillators from the 780 along with an extension keyer board, crippling the 780. You would also have to make some sort of keyer to drive the extension keyer from the 750 pedals, and tie into one of the preamps. You would also have to have that keyer key the top 8 notes of the great flute, as the extension keyers are just 24 notes in the 780.

The P16 tone cabinet is 35-1/2 x 23-1/2 x 23-1/2 with two 12 inch woofers and no crossover. So it has an internal volume of 9.8 cubic feet. Two of this woofer, or one in a cabinet of half the volume, will get you down to 32 Hz easily at a very reasonable price: https://www.parts-express.com/dayton...oofer--295-320


The P32 cabinet is larger (47-3/4 x 31 x 25) and has two 15 inch woofers.

By the way, the technology of the LTG organs is really easy to understand. The key and stop information is brought into the microprocessor via a serial data stream using shift registers, and keyed out to the tone keyers using shift registers. All the difficult technology is in the programming for the microprocessor, which you need not understand to work on these instruments. All of the actual tone generation and keying is then the same as earlier models, though the filters are active filters rather than passive. The microprocessor and shift registers just replace the wires.

[kiaya611]

Rodgers 750BE and 780

Toodles,

I was just more "thinking out loud" than anything. Some of the organs we get are in a state that they are really not repairable (these two don't fit that category), that I sometimes think of seeing what I could do to make a functional instrument out of what IS working on a few of them. Usually, we just save the good parts for others that might ned them later as we continually get instruments.

Since you have such specific information on these two instruments, does that mean you have manuals for them? I have yet to find technical manuals on either and I only found a users manual on the 750BE. I haven't even been able to find brochures or specifications. I used to be able to get manuals from Rodgers, but now they have gone the route of Allen and will only provide them to their authorized technicians, even though some of these organs are 50 years old and have been very long out of production.

If you have any sources (or secrets" that you are willing to share, I would appreciate it. You can contact me privately from my profile page.

Thank you,

Steven

First, I would strongly discourage you from trying to move the Contra Bourdon from the 780 to the 750B. The 780 is a far more complete organ than the 750B. The 780 having these stops over the 750:

Pedal
32’ Contra Bourdon

Swell
8’ Gamba
16’ Vox Humana
8’ Post Horn
8’ Vox Humana
Glockenspiel (if it hasn’t been separated from the console)
Swell Alternate Mixture

Great
2-2/3 Quint
8’ Harmonic Trumpet (from Swell)
8’ Vox Humana (from Swell)
16’ Piano/Harpsichord (available on Pedal if you elect to do so)
8’ Piano/Harpsichord
Great Alternate Mixture

The only two stops the 750 has that are not on the 780 are a 1-1/3 ft. and Cymbel II in the Great. I think you’ll find the Great Alternate Mixture is a suitable substitute for the Cymbel II. All the other stops are the same, though they have names that match the theatre organ style. In addition the 780 has 61-note celestes whereas the 750 is just 37 notes—the middle 3 octaves.

In addition, the 780 has a console that will fit through a 30 inch doorway and that can be very valuable. It has a more complete combination action, and many useful programmable features.

The 780 is part of the LTG (Linear Tone Generator) series of Rodgers organs, and it does not have any technology that is "experimental"--everything it has is used in other organs of that series: the 100 Series Organette, 650 York, 705 Kent, 740 Glasgow, 745 Concord, 755 Concord, 760 Concord, 770 Exeter, and 840 Windsor; the 650, 705, and 740 even have A & B version models. The technology was used from about 1983 to the end of the decade. Other organs used the same technology, too, but didn’t use the LED stop tabs. The 780 is only unusual in that it was specified as a hybrid theatre/classical model, so the stop names and voicing adjustments mostly are voiced to sound like a theatre organ. It also has color coded tabs—but you can adjust the voicing so it sounds just like a classical organ of that series. The 780 was one of the early models of this group, so its design dates from around 1983.

To accomplish this change, you’d have to remove the 32 ft octave of oscillators from the 780 along with an extension keyer board, crippling the 780. You would also have to make some sort of keyer to drive the extension keyer from the 750 pedals, and tie into one of the preamps. You would also have to have that keyer key the top 8 notes of the great flute, as the extension keyers are just 24 notes in the 780.

The P16 tone cabinet is 35-1/2 x 23-1/2 x 23-1/2 with two 12 inch woofers and no crossover. So it has an internal volume of 9.8 cubic feet. Two of this woofer, or one in a cabinet of half the volume, will get you down to 32 Hz easily at a very reasonable price: https://www.parts-express.com/dayton...oofer--295-320


The P32 cabinet is larger (47-3/4 x 31 x 25) and has two 15 inch woofers.

By the way, the technology of the LTG organs is really easy to understand. The key and stop information is brought into the microprocessor via a serial data stream using shift registers, and keyed out to the tone keyers using shift registers. All the difficult technology is in the programming for the microprocessor, which you need not understand to work on these instruments. All of the actual tone generation and keying is then the same as earlier models, though the filters are active filters rather than passive. The microprocessor and shift registers just replace the wires.

[toodles]

I do not have a tech manual for the 780, but do have the "so-called" tech manual for the 770 which is all but the same model, the one with the classically named voices and stoplist. As far as I know, Rodgers never really published a complete tech manual for the 770 and 780, just a set of schematic diagrams and a data chain list so what is available is lacking all the detailed description of the theory of operation and troubleshooting info.

I do have a tech manual for the 750B organ.

Unfortunately both of these are hard copies. I do not have the facilities to scan these manuals, as they includes some C-sized drawings (17 x 22). I suspect that one or more of our members have access to the Rodgers technical data site and may be able to get pdf copies of the manuals for you, but I do not have access to that site.

Certainly it is feasible to use one organ to provide parts for another organ either for replacement or expansion, but I do suggest that you try to stay within the same general series of models. But be advised that this is not a "plug and play" approach--moving a set of oscillators or a keyer frequently involves many wired connections, and if adding much circuitry you need to be sure the power supplies can support the additional current. It is an engineering project, not a simple repair project.

Here are the brochures for these two models. My sources for info have been many different folks over the past 20 or so years, often people on this forum. So this is the best source I know of.:-)

[snacks]

Steven, was this 780 listed for free in Salem, by any chance? I saw it posted, but I was traveling with a band and don't currently have space.