Coin-Operated Phonograph Explained: How The Jukebox Works

Monday, December 07, 2015

Growing up watching telly in the mid 1980's I remember the TV series Cheers and the beautiful music machine they had that they never hardly used! A Jukebox is quite literary a coin-operated music box with gears, motors, wires, tubes and a turntable that would play music from a self-contained vinyl record selection after a coin was inserted. The jukebox sounds simple enough, but you would be surprised to learn what a complex piece of machinery the jukebox is and how intricately and cleverly was put together!

The jukebox consists mainly of a sound system and two mechanisms: the player mechanism motor and the coin mechanism motor. The typical coin mechanism of a jukebox consists of a three-way coin slot that would take 5¢ (nickel), 10¢ (dime) and 25¢ (quarter) coins. Once a coin is inserted in either the nickle, dime or quarter coin slot, it travels down the coin mechanism falling into a funnel and directed down into a slug rejector. The slug rejector assesses the coin denomination by weighing the coin's diameter and thickness before letting the coin pass down through a shoot into the coin grinder (operated by a motor). If the coin is rejected, the slug rejector sends the coin through a different scoop out into a coin return cup.

How a Jukebox coin mechanism works
The top of the coin grounder has different slots for the different coin denominations. Each of these coin slots go down to a neoprene rubber wheel (located in the center of the coin grinder) so, when a particular coin is inserted it goes into a rotational path activating electrical switches. Each coin denomination activates one, two or five electrical switches to distinguish them from one another. For each switch activation from a coin, a cogwheel with cut teeth (also located in the coin grinder) would advance one, two or five times for each coin value before falling into a cash safe box where the coins are collected. For example, if you were to insert a dime (10¢) into the jukebox, the dime would activate three electrical switches thus advancing the cogwheel three times so the record would play three times.

How a jukebox record is selected
After the coin is inserted and accepted, the "make selection" light will illuminate and stay lighting as long as there are credits in the jukebox. The "make selection" light activates all the different music selections available which are selected by pushing a button. The music selection buttons was typically around 24 buttons (switches) which would correspondent to 24 music records on the record stack of the jukebox.

Each of these 24 buttons/switches are connected to a "selection drum" consisting of 24 coils, 24 rods, plates and a master switch which get activated once a music selection button is pressed. As you press a button, its corresponding coil is energized making its corresponding rod push out the back a spring-loaded rod. As the rod protrudes, it pushes two plates together which in turn energizes the master switch controller of the jukebox and switches the jukebox on.

The spring-loaded rod holds the music record selection down until the record is played entirely before returning to its starting position. One could actually have more than one music selection playing. For example, if you were to have four record disks selected on the jukebox, four rods would be released (one record disc would be held down until all four records have played and the fourth and final rod has been returned to its starting position).

After the record is played, the cogwheel and coin grinder reset and turn off the "make selection" light until another coin (or coins) are inserted in the coin slot.

How a Jukebox record player mechanism works
The jukebox is able to find the correct record to play thanks to the record player mechanism which is located at the rear of the jukebox and consists of a selector bank coil, cardioid cam, metal arms, a selector rod and a star wheel with bevelled edges. The cardioid cam (also called heart-shaped cam) lifts and lowers a the selector arm that is connected to a rod which has a small metal adjustable unit which scans up and down the rear of the record disk stack as the heart-shaped cam rotates.

The star wheel has 24 teeth and it's responsible for accurately centering the small metal adjustable unit of the selected record tray. A large metal arm is moved by another cam and swings the record out in position to be played. The turntable then rises up, lifting the music record to the needle to be played. Once the record is played, the record goes back in the record stack and the cycle is repeated when another selection is made.

The turntable is operated by cams along rods connected to a spring-loaded arm which controls the lift of the turntable. The mechanism resets for the next record thanks to a shut-off cycle where a tone arm gets to the center of the record swinging it all the way in and contacting another metal piece which then releases the shut-off trigger.

There are two universal joints, one at each end of a short drive shaft that connects the drive motor to the player mechanism. What powers the entire record player mechanism are several fiber cogwheels (one of them drives the turntable).

Jukebox sound system
A typical jukebox sound system consumed around 115 volts and could supply around 120 watts with a frequency range of 25 cycle, 50 cycle or 60 cycle (cycle refers to hertz). The main components of a jukebox sound system consists of a power transformer, a fuse, a tube phase inverter (or center tapped choke inverter), can capacitors, a rectifier tube to turn Alternating Current (AC) into Direct Current (DC), and several metal and/or vacumm tube power amplifiers (i.e. 6L6G's 6L6's, 6J5's and 6SC7's). The jukebox sound system also featured controls for tone compensators to regulate the bass and treble. The purpose of the vacuum tubes was to pre-amplify and boost the sound signal.

The jukebox sound system came with a typical 15 inch electrodynamic speaker which featured a 5200 ohms electromagnetic coil winding that also served as the filter choke for the power supply. The speaker typically had four wires going out to the sound system. Two of them going to the voice coil. The other two going to the electrodynamic speaker plug. The volume on the sound system (volume control box) was actually separate from the sound system unit and located on a more convenient location. The volume control box was operated/regulated with a key.

Interesting facts about the jukebox
The Jukebox truly and really has an interesting history and it's interesting to learn where the term jukebox actually came from, and the fact that the original name of the jukebox was coin-operated phonograph. It was during the late 1930's when jukebox or jookbox came into existence as a slang term in the Southern United States.
1952 Seeburg "C"

The jukebox also came in many shapes and sizes, though the most popular jukebox ever was and still is the Wurlitzer Model 1015 (also known as the bubbler) which I believe is still currently being produced by Wurlitzer GmB as the 1015 "One More Time" and is available for 45 RPMs vinyl disks or CD's. Other popular jukeboxes included the AMI Rowe, Rock-Ola Princess and AMI Continental II.

The jukebox was made for 3 decades from 1930 to 1960 and played mostly 78 RPM and 45 RMP 10 inch or 7 inch vinyl records.

Most Jukeboxes either take 78 RPM (10"), 45 RPM (7")Records or Compact Discs. Many 45 RPM Machines also took 33 RPM (7") "Little LP's" but these records were manufactured just for Jukebox operators and are very difficult to find.

Here is a video of a Wurlitzer Model 1015 jukebox in action:

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