Newly Acquired Allen T-15B

[David Jolley]

I just acquired an Allen Organ for home use. It is a T-15B, early model, likely built in the early 1960's. It is in surprisingly good shape for it's age. Only a thin layer of dust, and the voice generator is very clean. All of the pedals work, all of the notes work, and all of the voices work.

But... not all of the notes/pedals work for all of the voices, and it doesn't put out as much sound as I would expect.

I can recognize the difference between most of the electronic components, and have hooked up a set of home speakers to one of the outputs, but am clearly not an expert.

To help me I found another thread (years ago) with a similar organ and have tried to reach out to someone that says they created a manual (Jan) but have not heard anything back. I have also reached out to Allen without much success. They gave me the name of a representative in my area, but I have been unable to contact them.

I would appreciate any other suggestions on what I can do to get this organ to work well for home use rather than trial and error!

Thank you!

Dave

[toodles]

The Jan you speak of was probably Jan Girardot, who, unfortunately, passed away early this year. He was a very valuable and appreciated member of the forum.

The assembly in photo 2 of 5 (as numbered by the forums software) shows the pedal keying relays in the middle part of the photo. Each relay is, essentially, a 32 pole, single throw switch. The input to each pole is DC voltage from one of the pedal key contacts, and when the relay is engaged it connects 32 contacts (one for each pedal) to 32 different oscillators associated with the stop pitch. If some notes of some voices don't work, then the contacts on this relay are dirty or not making contact. If all 32 notes work on some voices, you don't have to worry about the pedal key contacts.

You can locate an organ technican at http://www.mitatechs.org/Service-Locator/

[Larrytow]

Dave,

Welcome to the Forum. When you say "in my area" , where might that be ? If you put your general location in your profile ( don't need to be exact ) sometimes people on this forum can help, or recommend help.

Of course, there is plenty of help available right here too. We have many folks here who know a lot about Allen organs, and they share information generously.

[engrssc]

Hi Dave,

Could be the missing voices are output on the other output/channel. Try connecting both outputs/channels.

Rgds,
Ed

[David Jolley]

I live in the Albuquerque area in New Mexico, thank you!

[David Jolley]

A little more on what I have done...

The pedals all will work for some voices, so I feel the pedal contacts are good. In fact nearly all the pedals work for all voices. I will clean the relay's and see if I get them all to work.
The keys seem random. F3 will work for all voices, but G3 only for one. The mechanical components are really clean and all seem to make contact well.

As far as sound goes. I have found two outputs, but wonder if there is a third (four cables that I think go to the rotating speaker assembly). This third I think is power, but may contain some audio. The other two outputs give the exact same sound, but I haven't yet got them to work together.

A thread about as similar organ suggested replacing the power supply to increase the volume. Is this a good idea?

Thanks again for your excellent advice as I work to get my first working home organ!

Dave

- - - Updated - - -

I'm so sorry to hear that. My sincere condolences. I appreciate the posts of his that I have read.

[jbird604]

The T-15 is an upgraded version of the venerable Allen T-12. These organs have only one "rank" of oscillators which produces a pure flute tone for each pitch, and the stop tabs turn on one or more of the coupling slides behind each manual in order to simulate a variety of organ tones by blending flute tones, a bit like a Hammond tone wheel organ, or like a small unit pipe organ with synthetic stops.

The T-15 is an upgrade over the T-12 in that it also has a reed/string output trunk on its oscillator assembly, in addition to the flute output. This is a secondary wave form that is tapped right off each pitch's flute oscillator but rectified so that it is a sort of quasi-triangle wave, thus the basis for some nice reed and string stops that are more realistic than the synthetic stops produced by the blending of flute pitches.

The generator system outputs two audio channels -- one for the pure flute pitches and one for the reed/string trunk voices. A T-15 might have two audio amps and speakers, or it might have a dual-input amp that serves both channels. In any case, there are two and only two audio channels involved. Each channel has its own volume control right on the amp chassis, so try turning up the volume until you get the desired amount of overall volume.

Missing notes can be due to several problems, but the most common by far are either (1) key contact issues, whether in the coupler slides or with the leaf switches stacked on top of the keys for the upper keyboard reed/string voices; OR (2) silent oscillators usually caused by a deteriorated keying capacitor. Either way, the problems are very easy to fix by a tech who knows these organs. Unfortunately, not every tech is familiar with Allen analog systems, and it's not easy to describe the fix to someone who isn't familiar with the way the system works.

Allen Organ Co should be more than willing to sell you a service manual, unless things have changed. They don't sell manuals to end users for their digital organs, but the analog manuals are freely available (though not free), and the manuals are quite extensive in their descriptions of the systems and the methods of repair. So don't give up on that route.

Bottom line -- you've gotten yourself a perfectly decent practice organ that can, with a little TLC, be restored to 100% like-new condition, something that can't be said for very many electronic products built more than 50 years ago! But it is also a fairly complex device, and you will have to be patient as you learn how it works and how to apply that TLC.

Good luck!

[David Jolley]

Thank you! I ended up replacing nearly half of the keying capacitors and every voice works for every key! It sounds great. The Allen Co Service Manual was helpful and I will likely need it in the future as it goes into a lot of detail. Now that I have spent some time with it an am beginning to understand it, it should be relatively simple to upkeep (knock on wood!), assuming I can find parts when I need them.

One more question if I may... for some reason the bottom 4 notes are a lot softer than the rest and I can't seem to find why they would have about 60% lower amplitude than the rest of the keys (An oscilloscope really came in handy for this part). Any thoughts on what might cause this?

Thanks!

[jbird604]

Do you see several small pots with a brass-colored shaft on the top side of the generator chassis? They are marked with note names and are used to control the amplitude of the very high and very low notes in groups of six. The lowest portion of the 16' rank would be C0 - F0 and would have its own pot. Try turning it to regulate those volumes. If that isn't it, it may be some kind of circuit problem in these particular oscillators.

[David Jolley]

That was totally it! Thank you! Just a bit of tuning now and I will be good!

[David Jolley]

Thank you for everyone's advice and help, but if I may ask for just a bit more! I have enjoyed this wonderful organ for the last few months, but today when I turned it on no sound would come out of it. The stops still work (the electromagnets engage), but I get no sound from any of the stops or pedals.

I have checked the fuses attached to the amplifiers which all seem OK, but I'm not sure where else to start. The book isn't as much help with the power system. Any advice on where to start?

[jbird604]

Check the amplifier by touching the terminals on top of the amp chassis where the expression capacitor is soldered in place. It should hum loudly when touching one side or the other.

[David Jolley]

It does on the primary amplifier, nothing on the other two similar shaped chassis.