Allen TC-4 Project

[Mr. Polecat]

Neat organ. I have a similar troll-like creature infesting mine, although mine likes to climb inside through the expression pedal hole and attack from that direction.

I see you have pistons on your manuals. Were these added as part of the MIDI conversion, or does this model have solenoid tabs? I've been trying to figure out what kind of solenoid tabs will fit my T-12a that I am converting to MIDI.....

[Silken Path]

Hi, Mr. PC - This organ (the '67) was not MIDIfied, but it did have full antiphonals. I started the thread with the freebie '59 that a forum member gave me. It turned out to be mucho project... now I'll be watching your project, too, as the ultimate aim to is to add MIDI to this organ.

On the '59, they went in on the keying terminals - snipping two of the wires and using the one that was left to connect to the MIDI board. There's a picture of the devastation near the front of this thread. I was pretty unhappy to discover it.

The tabs are operated by magnets and powered in both directions. (They were actually an option!)

[Silken Path]

Here I sit - listening to Pink Floyd without much bass.

I'm using a tiny scanning pocket FM receiver hooked up to the inputs of a T-20 Allen amp through a 60s gyro topper with 8 midranges and one Peerless (?) tweeter. I'm pleased that the amp fits the mounting holes and equipment shadow in the theater gyro. These were both in the grab-bag items that John B. included with the W500C and the big gyro when I visited. This amp will operate the hooters (horns) that have the flappers. So...

I'm going to have a complete antiphonal section in one gyro, for at least until I get three more amps and some speakers. I've been looking for some reasonable HC12s that aren't 500 miles away (Tampa). The organ has tabs for this - Flute and Percussion to Anti, Diapasons to Anti, Reeds to Anti, Organ F&P OFF, Organ Diapasons OFF, and Organ Reeds OFF. I'll need one more tab - I have a blank one to the right of these six - to power up the gyro, and one to power the flapper. (It could come on with the reeds since it's least likely that I'd select them without the flapper.)

I have six of these in a traps box. Would these be suitable to reuse to cut on or off speakers? (They do operate on 14V on the analog theater organs.) Or should I go with modern solid state relays?




And here's the T20 amp sitting in the gyro topper.




What exactly IS that stuff under the amps on this old equipment? (On the right in the picture above.)

And the midranges actually do have some bass response...

[Larrytow]

Lamar, your photos are not showing up. DSOTM probably sounds very interesting though a pair of rotating speaker cabinets.

[Silken Path]

Thanks, Larry. I deleted them and tried again. I could see them in Firefox, but not when I checked in Pale Moon or MS Edge. This time I left it at defaults. I hope it works now. Ended up listening to Aerosmith...

This is actually the box that sits on top of a small gyro on the little theater organs. It won't work on the big gyro I have because it would cover the upward firing hooters. Happily, this is the correct amp to power those horns.

[Larrytow]

Do you mean that sheet of white stuff stapled on ? I would figure it is a heat resistant shield. Could well be asbestos in that era. Pretty safe in that form, so no particular worries. Just don't grind it up and inhale it.

[jbird604]

Yep, sure looks like asbestos to me. I've noticed it in the bottoms of Allen cabinets before and never thought about what it might be. Considered a "miracle" material back in the day -- made wooden cabinets and building materials "fire-proof!" My high school, built in the early 60's, had asbestos ceiling tiles throughout the structure, considered the epitome of safety for a public building. Probably totally harmless under normal circumstances. But many people in the construction business, including my own father-in-law, became very ill in old age from being exposed to the "sawdust" of asbestos-laden building materials on a daily basis in their work.

[Silken Path]

I always was under the impression that asbestos was sort of metallic, fibrous looking, but I'll not mess with it. I got out the old Radio Shack power supply to test the relays. They were mounted upside down in the box and were shock mounted.

[Silken Path]

That's what I was wondering...

Here's the schematic showing the complete "traps cabinet" that I have. The solenoids are open-type and run on 14V from the organ. Using these would provide six of the relays I need for the antiphonals and main speakers, but I wonder, due to the application they were used for -- castanets, wood blocks, tom-tom, sand block, bass drum -- if they were designed to be activated for continuous duty. I imagine that these will sound neat activating, but would modern relays provide a great advantage in efficiency and longevity?

[Silken Path]

Well, I pulled one of the relays out, and it's labeled "Type 48, Telex/Aemco, 12 VDC, INTERMITTENT." It's beautifully designed, but does not appear to be what I need for this project.

[Silken Path]

Guys, would this kind of relay work for the audio signals? It's by Uxcell and comes with the base and screw terminals. They are $8.85 at Amazon.

[jbird604]

That looks pretty good to me. That one has the distinct advantage of screw terminals. I have bought similar-looking modern relays to use for speaker switching, but usually got the ones without a mounting base and just (carefully) soldered the wires to the pins on the bottom of the relay ice cube. Modern relays like that typically use far less current than the old Allen relays, which depended on those very heavy power supplies in the console floor to supply all the current drawn by those things (along with all the magnets that were used to operate the slide switches in the keystacks and other places).

[Silken Path]

Thank you, John. I'm going to order a very similar one that has the kind of connectors where you stick in the (tinned) wire and tighten the screw. It has slightly better spacing and, like this one, DIN mounting so I can get most of them in a row on the equipment shelf. Two will need to be in the gyro to operate the AC switching for the two motors. (I have about 50 feet of four cables coiled up between the organ and the equipment shelf. I couldn't bring myself to snip them...)

[Silken Path]

I also want to convert the T50 amps to a more common connector. I have a set of tools for installing BNC ends and some spare connectors. These are rated for RF video - should that work with these preamp equipped amplifiers for audio? (The coax is RG59/U. The connectors I have are the Klein red, universal ones.)

[Silken Path]

The reason I changed them is because the mini-Jerrold connectors used on the amps and on the coax are obsolete, and these were somewhat difficult to get started. Also, two of my amps and the spare amp are dual input models. I'm going to try sending some piano music from my laptop to one of the channels (so I can play along/develop/enhance accompaniment skills.) It's a Baptist thing to have a great pianist and a temporary organist. That's a joke, but not so far from the truth. The churches, by and large, DO tend to have a skilled pianist. AFuller's church, which is about 15 miles from me, is an exception - the organ is primary there, and he plays it.) I also plan to go multi-channel in Hauptwerk, and the big speakers from the Allen will give me three (now) to six (when I get the antiphonals all working) more channels.

[jbird604]

Good idea. Yes, the connectors Allen used back in the analog era are obsolete and hard to deal with. Best to replace with modern parts that are available and much more practical. And they do "sound better!"

[Silken Path]

Well, I ordered 3 x 100 ft RG59/U cable from Parts-Express. These were "Gemini" branded, like you used to see in electronics departments in big box stores. It's coming "SurePost" where UPS drops it by your post office and MAILS it to you instead of delivering it. I was also surprised to see the coax was made in America. Most of the RG59 sold now is "Siamesed" with 2-conductor power cables for security cameras and is China-express.