Allen TC-4 Project

[Silken Path]

Seems I'm being haunted by a small troll-like creature under the pedal board. Here is its appendage.



And here is the horrific face of the creature.




I think it's a sock monster.

In terms of what's new with the project, I took the reeds off the theater gyro rotor but left the top-facing horns attached to that channel. The reeds sound prettier now - the tone from the large hooters in the cabinet is more mellow that the modern horns. I've never heard the gyro on an Allen theater organ, but the reed chorus on the TC-4 is much more couth with the single stationary speaker and the ancient horns.

[myorgan]

That's a new type of snake I've never seen before. Weird head, though!

Thank you for sharing the update on your TC-4s. It is interesting how two seemingly identical organs can sound so different depending on the audio equipment.

[74corvette]

Silken Path'
I was just looking at the first post, page 1. You were looking for a manual and any other info. When I had my Allen T15, I bought the Allen Tech Package. It includes;
Service Training Series, Analog Pre Training Primer
Service Training Series, Analog Service Manual
Schematics are abundant in these manuals
Also a lot of loose info From Allen.

I have not read all 22 pages and I dont plan to as I no longer have the T15.
If you could use these manuals to get your running, I will be happy to send them to you..... Freebe
PM me with your US Mail Address.

If you dont need these, the offer is then open to anyone here that can use them. They will never be needed by me as I have the Allen 705D and 1871 Estey

74corvette

[Silken Path]

Thank you. I have all those now, but I think I know somebody who would be interested... I'll check.

OK - I was thinking of skaterdad and his wife's sister's TC-1 (or something like that) but I see he hasn't been here since 2017. I'm sure that somebody with a need will appear, since it covers ALL the analog models. Thanks again.

[Silken Path]

I've never heard the gyro on an Allen theater organ, but the reed chorus on the TC-4 is much more couth with the single stationary speaker and the ancient horns.

I experimented with this more today. I still don't have the 14V going to the relay for the horns on the theater gyro, but the reeds sound great with the two horns sounding with the "stationary tremolo" reed speakers. Sound great, that is, when playing the right hand of hymn music. It gets busy fast with the left hand added to the same manual. I'm supposing that the the Bombarde, Trumpet, and Clarion are the "reed chorus" that I've seen reference to here on the forum.

What would a reed chorus typically be used for in hymn playing?

Next I'm going to try the theater gyro with the flutes and diapasons on the rotor. (I think it was used for flutes and reeds, and flapper was on reeds, too.) Interestingly to me is that the reeds don't sound great on the gyro.

[AllenAnalog]

I find it most interesting that you are not happy with the reeds on the gyro. My theater organ has two tabs for the flute channel to select the stationary upwards firing speakers, the single speed AC gyro or both at the same time. The string channel has a DC gyro with multiple speeds and no upward firing speakers.

The reed channel had the electronic tremulant from the board on the Whind supply. It was disconnected before I bought the organ and I've never had time to pull that big heavy console out from the wall to work on it since it's on carpet and the pedalboard is wired, not magnetic.

Once I am in my new home I was planning to use one of the "new" DC gryo cabinets I got on ebay for the reed channel. It has the upward firing Jensen horns (no flappers) and a 3-speaker gyro disk. I would then hook it up with the same controls as the flute channel - horns/gyro/both to see which I like the best.

So what is it about the sound of the reeds you don't like? Too fast? Too fluttery? Your answer may save me a lot of work leading to great disappointment.

[Silken Path]

Hi, Allen - Well, I just have a theory - but a reed pipe has a vibrating tongue that moves at a certain frequency. Allen seems to have done a good job on imitating this, and it's pleasing to hear, which I didn't really expect. If one listens closely, the beat from the reeds survives the "tremor" from the tremolo from the Whind generator. (I have some keying capacitors to replace, so I'm using minimum Whind, but more tremolo depth, for the time being.) My perception is that a lot of the "pretty" goes away when the reeds are added to the rotating channel - which adds yet another frequency. Now I've wondered why it's not all pleasant and soothing like the big gyro spinning with the flutes. The flutes are smooth sounds, as are the diapasons.

So today I'm going to put the flutes on one side to test. (The reeds still sound good on the vertical horns.)

Is it possible that an Allen theater organ is designed to sound more gritty than a church organ? (Is it possible that I simply don't know what I'm talking about?)

[myorgan]

What would a reed chorus typically be used for in hymn playing?

A fanfare is a possibility. The opening to the hymn, God of Our Fathers, is a prime place for a Reed Chorus to be used. In the absence of a Festival Reed, a Reed Chorus could be used to solo the melody, or even coupled to the Pedals for a Pedal solo.

Michael

[Silken Path]

Thanks, Michael. Hmm... I've been dissatisfied with a trumpet (solo, festival, trompete) on the other manual on that tune because it's such a difference in volume over an ensemble, requiring rapid jockeying of the pedal before and after. I like that so much that I'm going to go try it on the Allen.

[toodles]

The first Allen organ I played was a TC-4 at my church--it was newly installed around 1970. As I recall, the gyro was only used on the flutes in that installation--principals and reeds had only stationary speakers. The organ also had the whind tremolo.

Try the reeds at 16-8-4 with the mixture, if they are all available on the same manual--no other stops.

[myorgan]

I don't think the TC-4 had Mixtures. If any, on the Great only.

Michael

[Silken Path]

Thank you, gentlemen. This organ has Mixture II, Bombarde 16, Trumpet 8, Clarion 4 all adjacent in the Swell. It also has the Mixture II, Bombarde 16, and Trumpet 8 on the pedals. (The '59 has twelve stops on the pedals!) I have a 1963 TC-4 brochure that shows the organ coming with the same stops as my '67, except mine does not have any of the 1-foot stops on the tabs.

I tried the three reeds on "God of Our Fathers" and it was a nice, strong effect with volume more like the diapason ensemble I like. Thanks, Michael. I could see that working in the churches I've attended.

Toodles, I added the Mixture II to Bombarde 16, Trumpet 8, and Clarion 4, and I'm not too sure... it sounded a little more synthetic and electronic than the reeds by themselves. It does "fill it out" some. I'll have to experiment with it more, and it may sound better after I do some of the caps.

Allen, it looks like the gyro had a T-20 just for the horns. I have it in a separate box with a traps box now. That previously mentioned brochure had the organ coming with two gyros. (They said it was stereo. )

It's supposed to be the coldest night of the year tonight. Happy Martin Luther King Jr. Day, everybody.

[toodles]

I think the 2 rank mixture is probably a little too thin for use with reeds (alone); if it were IV it would be better, or even III.

[myorgan]

Agreed, Toodles. The III Cymbal (Cymbel?) would probably add a crispness to the ensemble.

Michael

[Silken Path]

Thanks, Gentlemen - I'm still experimenting with the furniture gyro, and I'm confirming what Allen originally sold it for.

Here's what I'll stay with.

1. Flutes on half the gyro.
2. Diapason on half the gyro.
3. Reeds on the horns with the flappers.

- I already have the flutes on the big gyro.
- The flutes already have the gyro, a sweet sixteen, and a bass speaker.
- The diapasons sound good on the gyro, but it already has a four-bass speaker and a sweet sixteen.
- The reeds sound *muddy* on the gyro. They are crisp on the single bass, horn, tweeter speaker.
- The reeds sound good through the horns on the furniture gyro.

So I will probably put the theater gyro about 12-feet to the side or about 15-feet to the rear. I will use the antiphonal control tabs that are already on the organ, and this will leave me free to add another DC gyro for the diapasons when I find one.

Ever onward...

[Silken Path]

Alas, the Whind-derived Tremolo has stopped working. I haven't found a diagram of this exact model (900-0064) but I do see some similar ones. All seem to have a lamp shown in the circuit - it's part of an LDR, I think - and the power is from the Tremolo tab on the organ.

I removed the red cable's square plug in the unit and looked for continuity across this lamp (tremolo control and ground). I didn't find any.

So the next thing appears to be checking the bulb. I see what I think is the LDR in a holder on the back of the tremolo module (the part that has the tremolo rate and depth controls on it). It's not readily apparent how it comes apart, and I don't want to break it. Here's what it looks like. (I think that's it just above the transformer and beside the black 100 mfd capacitor.)

So how does it come apart? Is that a bulb holder I see at the bottom of it?

Gee, is this a common failure or is the problem likely to be something else?

All this live and learn just kills me.

[myorgan]

Admit it, you love it!!!

[jbird604]

Remove the screw. The clip holds the tiny lamp in place. Yes, they do fail now and then.

[Silken Path]

Thank you. The bulb tests good, and there is 12.2 volts showing between the "control" terminals on the front of the panel, so power is getting there from the organ. I shall get my fill of playing it this morning, and then I will pull the Whind unit out to get a better look at it. It is providing keying voltage, and I have about 5 VAC on the meter for Whind level, so the next thing to look for is the voltage from the noise generator (20V) that powers the tremolo unit.

Onward and upward.

[Silken Path]

May have spoken too soon. Looking more closely at the bulb, it looks like the insulation between the center and barrel has concentric bare/worn spots... So we're not giving up on the bulb idea quite yet. #330 bulbs are elusive in "The town that Sherman refused to burn," so I ordered a couple from Amazon. And the unit does have 12.2 volts coming from the organ to this relay and 19.7 volts coming from the noise generator to the tremolo circuit board.

At least it's still keying and playable. It could be a lot worse.

Interestingly, there are also LED replacement units available for the #330, for about the same price as the GE automotive bulbs. Hmm.

BTW - does the noise generator make the Whind light on the panel vary? I've seen it stutter with the tremolo, but I've never seen it flicker or flash at random, such as one would expect to see sometimes when Whind is on.

[jbird604]

The little lamp probably lasts for 20 years or more, so not much use to replace with LED unless you just want to. The LED of course must have a resistor in series with it, but I assume that's included inside the replacement bulb.

Best I recall, the Whind light shines steadily unless the tremolo is on. I don't think the random noise variations of Whind by itself is enough to make the lamp flicker, though it might I suppose, if the Whind is turned up to maximum.

I don't recall ever having the tremolo go out on an analog Allen, so I don't have any wisdom to share. You'll just have to use the schematic and trace out the trouble.

[Silken Path]

Thanks, John. I moved the Whind module to the top of the shelf to make it easier to work on. From what I've been reading, the LED replacements simply drop in - for automotive applications. I may play around with that later. (This organ is 52 years old. It will probably outlast me.)

[toodles]

On the TC4 that I played, the Whind indicator lamp did vary in intensity a bit--not enough to flicker nor annoy, just varied in intensity with changes in the voltage. It pulsed with the tremolo when it was on.

I would not recommend replacing any bulb in the trem LDR circuit with an LED. LED's go on and off almost instantly while incandescent bulbs have thermal lag which filters out high frequency noise or signal--this may be part of the tremolo drive wave shaping included as part of the design. You can almost drive the bulb with a square wave and get a sine wave out of the photocell because of the thermal lag. Not quite, but almost.

The design of the circuit probably incorporates a much lower voltage on the bulb than it was designed for, assuring very long life.

[Silken Path]

Thanks, Toodles. I need to go back and check again. When I was looking for voltage on the LDR (to confirm my suspicion about the bulb) I had the tremolo switch on. I need to check with it off, too.

This LDR is labeled "relay" in the schematic... That suggests that's in on or off.

Thanks again. It's great to have you and Michael and tow Allen around with experience playing these exact models.