Piano Board - DC current


How to read cue sheets written for Piano Boards

In looking at lighting cues written for any shows in any Broadway theatres before 1974, bear in mind that the dimmers (channels) are all resistance plates running on DC current. These dimmer plates, grouped into consoles known as “piano boards” or “road boards”, were reputed to have been made for World War 1 submarines. Since resistance plates dim lights by turning the electric current into heat, the designer had to load these dimmers to at least their minimum capacity or the lights would not go fully out. The levels seen in the cue sheets are noted as 0 to 10 indicating resistance not brightness. Therefore 0 = FULL and 10 = OUT or maximum resistance; 5 = 50%, a reading of 7 = 30% and a reading of 3 = 70% brightness.

These ‘Piano Boards’ were manually operated (click here for a video of Gus Popiel, production electrician for 40 years reminiscing about running manual boards). Traditionally one man, by standing between them, could operate two 14-plate 1500 to 3000w boards with two auxiliary boards on top of each one, a total of 28 large and 24 small dimmers. The other standard was a 12 plate 5k or 6k board.

The ‘Auxiliary boards’ were 12 plate 500w dimmers or 8 plate 750w dimmers making it possible to dim single units. The ‘aux boards’ were plugged into several of the large dimmers functioning as masters. Additionally, these single unit dimmers would be plugged and replugged through the evening to maximize their use. In the Rosenthal sheets the replugs are identified by color (ie the white plug or the black, the yellow or the red). Because the main dimmers had to be loaded to capacity the designer had to anticipate the use of groups of lights that would always work together, for instance, High Sides of a similar color that made a complete wash of light from down to up stage. In fact this is the origin of the use of the words “wash” and “specials” to describe Lighting concepts.

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