Allen Organ 632-D won't power up

[Thomas28]

I finally got the bugs worked out. I had to have the power supply rebuilt and replaced one of the main boards. It is now a joy to be able to play! Is there any way to add celeste to the swell manual?

[jbird604]

Glad you got it fixed at last. The 632 was a really under-appreciated MOS model. At the time, I tended to look at it as simply another "bargain-basement" three manual, since Allen had sort of re-purposed the MOS concept in this design, building a three manual organ with the parts originally intended to make up a two-manual (model 600, 603). It seemed to me to be a shadow of the more fully-equipped three-manual models such as the 900 and up. But I was wrong to sell it so short.

Because of the way the MOS systems are re-purposed in the 632, there is no "doubling" effect, as found in all other MOS organs with more than one computer system. On the regular 600/603 and other doubled organs, every stop in every division is being simultaneously produced by BOTH computer systems. To produce a celeste in this type organ, it was a simple matter of flipping a tab that altered the tuning curve of one of the computers, creating a gorgeous and flawless celeste to rival any pipe organ's celeste.

But in the 632, each of the two computer systems works independently, with one system providing the great and choir stops and the other one providing the swell and pedal stops. No doubling means no obvious way to create a celeste.

On the choir manual you may have "celeste effect" -- though this stop was optional and some purchasers chose not to include it because it has a major drawback: when engaged, it does make a "celeste" out of any stop you draw on the choir, but it cuts the polyphony to six keys down at a time. This is manageable, as long as you know the limits, and be sure NOT to couple the choir to the pedal while you're using the celeste, and NOT to play anything on the great manual at the same time. But not as nice as the genuine double computer celestes of the 600 and other large MOS organs.

All that said, you see why there is no celeste on the swell. It MIGHT be possible to implement a "celeste effect" similar to what is done on the choir. This involves triggering certain normally un-used coupler functions on the MOS system, along with another unused function called "sharp tuning." But this might be harder to do on the swell -- I seem to recall that the pedal division on the 632 is already using some of the non-standard MOS coupler functions. At any rate, it would take some study and some technical tricks that only a MOS expert would readily understand.

I've often thought that if I had a 632 of my own, I'd figure out a way to install a tab to "sharp tune" the choir while simultaneously coupling the swell down to it, thus producing a true double-computer celeste like other big MOS models, without the six-key limitation. But that too would require a certain amount of custom wiring into the MOS system. Probably best to just be happy with it the way it is and enjoy the lovely if limited celeste effect on the choir.

Or get a MIDI adapter from Harrison Labs and add new stops to the swell via MIDI.

[Thomas28]

John, Thanks for the responding so quickly! I might look into the Harrison Labs idea. I do have another allen organ that is a two manual 603? It does have 2 computers. I thought about selling it or would it be possible, within reason, to somehow put the two together? Thanks

[jbird604]

No chance of merging the two organs. Way too much involved. Each MOS system back in the day had to have its own dedicated set of key contacts (thus the 600/603 and other doubled organs had double-stacked key contacts on both manuals). And isolation between multiple computers must be maintained with signal diodes on every stop control line or other organ feature control. It would be tantamount to totally building up a MOS organ from scratch. Obviously, someone COULD do it, given the time, money, equipment, engineering skill, space inside the console (which is not available in the "D" console), and so much more. But it would certainly be a very expensive proposition.

What you're talking about creating is in fact a MOS System 1200, a "four-computer" model, basically the same thing as the 632, but with TWO computers assigned to the great/choir and two assigned to the swell/pedal. That system could indeed do everything your 632 does, plus produce genuine two-rank celestes on all divisions. These big monsters occasionally come available somewhere. In fact, there have been folks in the past who posted about them on this forum. I'm sure such a beast would be quite an awesome instrument, but in reality today's Allens (or even those from the 80's and 90's) are capable of doing far more with a lot less circuitry and a lot less weight and bulk. And are sometimes available for not too much money.

Owning two MOS organs as you do, you could save the 600/603 as a parts source, since it holds virtually all the same components inside as your 632. If you ever need a MOS board or other circuit board to keep your 632 playing, you'll find that they are quite expensive from Allen, so having your own backup stockpile is good long-term insurance for the organ.

Or you could sell off the MOS boards and other items inside one or both your consoles, and use the money to buy a modern MIDI kit and turn the empty console into a marvelous MIDI driven VPO. These days it makes little sense to spend time overly customizing an older organ, especially when you're talking about tons of hardware mods, when it is relatively cheap to build up a VPO once you get hold of a good console to use as a base. And you certainly have one (or two) already!

But just adding MIDI to the swell division only of your 632 would be relatively cheap and easy. Harrison Labs has an adapter that works on MOS organs. It comes in versions configured to MIDI up one, two, or three divisions. You would need two of the boards to do all four divisions of the 632 of course. Then you could get the stop control adapter from Zuma Group which will MIDI up your stop tabs or drawknobs and even integrate the expression shoes into your MIDI system.

Many years ago I was playing an old Rodgers analog at a church, and I wanted more stops. I got a kit from a guy in Poland and MIDI-ed up just the choir manual of that Rodgers. Back then I was playing around with the "j-Organ" VPO system, and I created a little ancillary division of 6 or 8 stops to add to the existing choir. I gave it great chimes, a lovely Festival trumpet, a rich celeste, a unique mixture, a chiffy flute. Had a lot of fun with that, though I never fully integrated it into the console. Just had a touch-screen monitor sitting on a little table beside the organ. It sure did help make that old dog of an organ more interesting to play.