Restoring Classic Carousel Cart Machines

The Carousel cart machine was a staple of radio station automation systems in the 1970s and 80s. It provided the means to play back a large number of tape cartridges without operator intervention. The Carousel (shown above from a catalog listing) was manufactured by SMC (SonoMag Corp.) of Bloomington, IL, beginning in about 1968. The device could hold 24 cartridges that were played sequentially—or through optional equipment—in any random order. A single Carousel machine could not play carts back-to-back due to the required re-cuing of the cartridge, and the mechanical action needed to move one cart out of the playback unit and another cart in. With two Carousel machines, however, they could ping-pong back-and-forth forever.

There were a number of high-capacity cartridge playback machines in the early days of radio automation. The Carousel defined the “one tape head” class whereby an inventory of cartridges was moved (by various means) to a single playback device that included the tape heads and capstan/pinch roller assembly.

A second class of multiple playback devices approached the function from a different perspective. Rather than move the cartridges to a single playback unit, a playback device was provided at every cartridge position. The IGM (International Good Music, Bellingham, WA) Instacart defined this class of machine. The Instacart would hold 48 cartridges and play them in any random order, back-to-back. This was accomplished by having a single capstan motor for each bank of 12 cartridge positions (four banks in all for a total of 48 carts). Each position had a playback head and pinch roller/solenoid to engage and play the cartridge. The audio for each position was switched into a single output stream. The Instacart was a maintenance challenge, with all those tape heads and capstan positions to clean. However, since the workload of the Instacart was spread over 48 elements, the actual wear on each playback unit was relatively small.

The Carousel and the Instacart represented the two ends of multi-playback technologies. In between, there were variations on each theme, suited to individual use cases and price points.

It came to pass that three SMC 350 Carousel cart machines were offered for sale by a radio station not far from me. The price was reasonable and shipping costs were not prohibitive. I had already acquired and refurbished one 350 as part of the 1970s Automation System project documented in another blog. I had found the 350 to be reliable and well-built. And so the project began.

shipping crates

Like all of my projects, this one started with shipping crates full of stuff. The first challenge was getting the machines in a position where I could work on them. Each Carousel machine weighs about 95 pounds, and so moving one around (let alone three) is a challenge. Due to the weight of the 350, special considerations apply to mounting in a rack. A mounting bracket is required on each side of the machine and preferably secured at the front and rear of the rack. Not all racks will accommodate those brackets and so a custom bracket was designed and manufactured by Protocase.

Carousel machine in shipping crate

The physical layout of the 350 makes it difficult to do much work on the assembly unless mounted in its operating position. The project is therefore on hold until the mounting brackets and companion rack are available.

More to come…