Thomas tone cabinet amplifiers, can anyone Identify? - Colton Piano sigh

[Monarke]

I have a new customer with Ahlborn Preauldium 1 installed in their church. It was originally sold as a demo organ and installed by the LURVLY people at Colton Piano of Corona California. The instrument has never been serviced since it's original install date. There are two Thomas tone cabinet amps installed in the console, much modified wiring etc. I have not had a chance to yet "crawl" up to where the loudspeakers/tone cabinets are installed as this instrument has many problems.

Does anyone recognize these amps, from which tone cabinet they might be installed in and what era? While the organ is late 1980s, these amps appear to be 1970s technology. There is also a Leslie control center installed. I suspect these tone cabinets may contain Leslie spinet rotors too.

The amplifiers do have AC breakers which can be clearly seen. I don't know how much fixing up I should do. The mods seemingly works *at the moment*. The organ itself needs TLC first, many of the 'grasshopper springs" in the pedal board are broken. The piston memory battery is leaking, intermittent playing manual problems (silver busbars). There can heard a thump thump thump sound as the Leslie animation starts. I'm sure this part is in need of attention too.

Wire splicing and shoving into connector holes.

Double sigh....

One nice plus is this customer pay on the spot.

[tucsondave]

It's definitely a monaural Thomas organ expression pedal amplifier. Looks like the line level input has been modified with a matching transformer to accept a speaker level signal. I started servicing Thomas organs in 1968 and never saw an amplifier like that so I would guess it's from the mid 1960's. Also I never saw a 24 pin Molex on a Thomas amp or a power transformer that large. Thomas did use their modified expression pedal assembly in some Vox speakers so that is also a possible source.

td

[Monarke]

Obviously I misunderstood the sticker which explains "Use only with Thomas Organ tone cabinets".

There are two of these beasts mounted vertically inside the console. One on each side of the expression box.

I suppose the two holes in the chassis might be where the expression pedal was mounted, and the black plate is a back shield?

It seems to have two RCA input connectors. If it is 1960s one small transformers might be inter-stage and the other part of the driver section, as CBS/Leslie did in their transistor amplifier designs. They seem to small to be output transformers.

Modification to accept a loudspeaker level signal would be unnecessary. The Prealudium 1 has an outlet panel with RCA connections for preamp a level signal. At first glance this panel seems to be missing.

It appears the two blue wires are pushed into the Molex connector for the output. They could also be pulled through and soldered underneath. I didn't do any "tugging" on wiring, as this instrument has numerous problems already.

The internal loudspeakers do not work. The organist explained "they haven't worked in quite some time".

It's anyone's guess what is connected to the other end. To be determined on my next service trip. Hopefully not too much dust will be consumed during the process. ;)

[Monarke]

It's definitely a monaural Thomas organ expression pedal amplifier. Looks like the line level input has been modified with a matching transformer to accept a speaker level signal. I started servicing Thomas organs in 1968 and never saw an amplifier like that so I would guess it's from the mid 1960's. Also I never saw a 24 pin Molex on a Thomas amp or a power transformer that large. Thomas did use their modified expression pedal assembly in some Vox speakers so that is also a possible source.

td

I went looking on eBay and found this:

https://www.ebay.com/itm/185617872138

This shows a 9 pin Amphenol socket. If this is in line with the Leslie models it would have been late 1960s and before UL changed the rules about AC being sent in the same cable with Audio. In 1978 that changed and the 11 pin socket was adopted. Leslie speakers then had separate AC power cords and plugged into a wall socket.

The example I posted images of must be from the early 1960s as it has a 6 pin Amphenol socket.

The expression pot must have been removed from the two units used in the Ahlborn organ as I do not see it, nor do I know if there is a "whole" where it once was mounted.

Here is a second example which also appears from the style of solder lugs to have a 9 pin Amphenol socket:

https://www.ebay.com/itm/155110669806

[tucsondave]

On a closer look are there two more power transistors on the black part? That would explain the extra transformer and the two RCA jacks you mentioned. Then there's the lack of a vibrato rate control that the mono and later stereo amps had. There is also an empty pot mounting hole near the power transistor in the 2nd photo.

td

[Monarke]

I don't think there is. At the time of manufacture I think there was only TO5 style power transistor packages. When I go back I'll look closer, but I think this is a shield to prevent one's shoe from moving to far forward into the "works".