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PART I: HUB SWITCHBOARD OPERATING MANUAL


2500 light bulbs in the Atlanta Fox Theatre were controlled by the Hub Pre-set Selective Theatre Control (Resistance Type) or Switchboard for short, the nerve center of the Theatre.  Press releases asserted that “all the switches are fully protected, the operator being fronted by an entirely insulated board,” meaning that unlike its primitive ancestors of a mere ten years prior, the Fox board was dead front with slot-closing switches and dimmer control levers. The first operator so insulated was Cliff Clower, IATSE Local No. 41.  

A  dead-on front view of the entire board:
Photo by Irving Glazer, 1966, courtesy Patrick Seymour, Theatre Historical Society

The Hub Switchboard represented the state of the art in compactness, and its handsome appearance was in stark contrast to the ungainly boards of a decade before, an example shown here.

Architect Ollivier J. Vinour of the Atlanta firm Marye Alger & Vinour was responsible for the aesthetics of the Atlanta Fox, but consulting engineer C. Howard Crane was in complete charge of the physical layout and all details theatrical, as reflected in his preliminary 1928 drawing set.  Crane was the primary architect of the Brooklyn, Detroit and St. Louis Fox Theatres, and Vinour had worked in Crane's Detroit office.  

To see the plans of the Atlanta Fox Theatre as of 1929, click on
http://foxfact.blogspot.com/2014/12/complete-drawings.html  
[The Roxy, Brooklyn, and San Francisco were later demolished.]

Eugene Braun, the Electrical Supervisor of Fox's New York Roxy Theatre and a lighting designer before the term came into usage (and the first to specialize in musical stage spectacles)  traveled down from New York “to superintend” the installation of the Switchboard and all other stage lighting apparatus.  The New York Roxy Hub Switchboard (1927) which was claimed to be the largest in the world was a mere twenty inches wider than its younger brother at the  Fox, 20 foot, six inches wide.

Ward Leonard Electric, who manufactured the dimmers used in Hub Switchboards, also laid claim to the Roxy.

The mammoth Roxy Switchboard en route to New York City from the Hub Electric Company of Chicago.

Frank Decker was the man behind the Hub Electric, and Hub Switchboards were the top of the line.


Hub advertisements for the Detroit and St. Louis Fox Theatres which were identical twins.

The Atlanta Fox Switchboard was featured on this page from the 1930 Hub catalog.  Fully loaded and including un-dim and constant circuits, the alternating current section of the Switchboard drew 1600 amperes on each of its three phases, or a total pull of 572 KW (kilowatts).  DC capacity of 700 amps at 100 volts was sufficient to feed fourteen onstage carbon arc follow spotlights.
To see the complete 1930 Hub Catalog http://foxfact.blogspot.com/2014/12/complete-1930-hub-electric-catalog.html

The Fox also provided a 400 amp Company Switch for productions which traveled with piano boards, so named because of their great weight.  Resistance dimmers were constructed of vitreous china (glazed porcelain) set into cast iron frames and when dimmed ran hot.

Four vendors supplied the Fox stage lighting equipment:  Hub, for control,  plugging devices, Borderlights and Footlights; Kliegl for stage and house spotlights and floods; and Brenkert and Hall & Connolly for the three carbon arc Front Lights.  To read more about the Front Lights, click http://backstagefox1929.blogspot.com/2014/03/part-iii-talking-picture-projection.html

A diagrammatic drawing of the 200 dimmer Atlanta Fox Hub Lighting Switchboard.

To energize the Switchboard, one turned on the running lights toggle (shown to the right), then inserted the key into the lock switch (shown to the left).

The Switchboard was divided into five sections.

Detail of the left-hand or Stage Section.


Detail of the center or Control Section

On the top right-hand section of the Switchboard were the Houselights, subdivided into Picture House (those lights which remain lit when the house is occupied) and House Lights, which were dimmed out before the stage show or picture.

Picture House included the deep blue circuit of the sky coves, blue circuits in the balcony soffit and organ boxes and a portion of the rear ceiling (gallery) fixtures. Stars were simulated by one hundred and twelve 25 watt general service lamps with reflectors placed on the top side of the plaster sky, beaming through pin holes in the plaster and magnified by prisms  The clouds were projected onto the sky by two Kliegl effect machines containing "moving fleecy cloud" discs which rotated at an imperceptible pace.

House Lights included the light blue circuit of the sky coves, amber and red in the organ boxes, and a glow from the various windows set into the side walls.

Unique to the Fox was the auto-sunrise and sunset effect, achieved with dimmer plates operated by a motorized cam shaft which would sequence spotlights aimed at the sky into a series of cross-fades. Thus the sun would rise over the balcony (east) and appear to travel to noon position (auto-sunrise); hold for a given period; then set over the stage (auto-sunset). The Switchboard operator, cued by automatic electric buzzer, would fade the House Light dimmers up or down in synchronization with the motorized sunlight effect spots.  The motorized dimmer assembly was located in the Power Room beneath the Switchboard.
Overhead and balcony "floods" were actually plano-convex (PC) spotlights, twelve 1500 watt units in each position ganged in groups of six, as well as four 2K specials for organist and band leader.  Gel color changes were preset and controlled from the board.   A five prong pin plug connected the color changer.

The Stage Side Bridge positions consisted of permanent platforms at 12 and 24 feet, bringing the high outside position to just shy of thirty-six.  Each Bridge was circuited for 16-1500 watt PC spots and one 2K circuit, dedicated to projecting clouds or other effects onto the cyc. Two circuits per side were provided for DC follow spots. 


The lower platform of the PS (prompt side) Side Bridge.

This plan shows the locations of the Switchboard, Side Bridges, Cyclorama Footlights and Floor Pockets.
Drawing by Garry Motter

The left hand portion of the Switchboard contained the stage section

which was divided into four color banks, a mark of a deluxe house.  Most Switchboards of the era were red-white-blue.

Twenty dimmers and 106 circuits were allotted to the five Borderlights.

The Valance Borderlight utilized clear 200 watt lamps and was a smaller version of the four others which burned 300 watt lamps.  The excellent copper and glass color screens were an exclusive to Hub.

On the upstage edge of Center Light Bridge, two by eighty feet, was the hanging pipe for the PC spots circuited to a connector strip which ran the full width.  DC connections for four carbon arcs were equally spaced, and the bridge was flown on a special lineset with a 3-2 ratio so that it could be operated without re-weighting to allow for the load of the four spot operators.   

There were eight "Inc" (incandescent) Floor Pockets, two upstage and three each side,  four of which were five-gang and included an un-dim circuit.  Six DC pockets were also provided.  Inc Pockets illuminated when the lid was lifted, and jewels indicated the circuit color.  Five gang pockets were a deluxe feature, and lighted pockets were another Hub exclusive.

Eight dimmers and 72 circuits controlled the Cyclorama (left)  and downstage Footlights (right).  Two dimmers (not shown here) controlled the four outlets in the downstage Footlights for pin spots.


The Footlights could disappear via a hand crank control located on the ceiling of the trap room below.

A truly deluxe feature were the Cyclorama Footlights, shown here with only stage right traps open. The traps were damped with door closers, so that a stagehand could run along the upstage and push them to close without the attendant slam.  The foots themselves were portables in eight foot sections, and there was a well of sufficient depth on the upstage to allow the 44' x 84' motorized steel-framed Cyclorama to land there, below deck elevation, obviating the necessity of a scenic ground row.   The traps could open only to a 100 degree angle which allowed space for an actor crossover.  The stagehand pictured at the normally locked entry to the Shrine dressing rooms gives one an idea of the scale of the Side Bridges.

Boxed on the left are dimmers for the Proscenium Spots, a vertical stack of eight PC spots located on the downstage edge of the Side Bridges which gave out a strong sidelight for the very important IN ONE playing position.   Four special low wattage dimmers, non-interlocked, were from left to right, Orchestra Stand Lights fed by miniature pin plugs spaced along the pit lift; Emergency Lights, which allowed exit signs to be killed for a total Roxy-esque house blackout;  Stars, like those above, located within the hard cyc; and Minature Outlets, a board pocket designated for low wattage stage practicals. 

Rehearsal letters stamped within the Pilot Lights for the primary stage circuits corresponded to those on a lighted Fox rehearsal table, so as to facilitate technical rehearsals.  Backlit and numbered gel colors were shown closest to the stage director, in this case Leon Leonidoff at the Radio City Music Hall (1932) where Roxy's LD Eugene Braun spent the remainder of his long and distinguished career.   The Fox was equipped with a "God Mic" for the director.

Direct current for the Fox stage carbon arcs was provided by twin Westinghouse 455 DC ampere Motor-Generator sets located beneath the stage and distinct from the booth machines.   Left to right, a typical MG set; the contactors which allowed DC lamps to be blacked out in unison with the incandescents; the stop/start controls for each MG; the Voltage and Amperage Meters above the board for each MG, which also provided current for the rail and cove gel change solenoids.

The Worklights were comprised of three Downward lamps equally spaced within each of Borderlights No. 1, 2, 3 and Cyc, and a deluxe feature were the four Upward works located on Borderlights No. 2 and 3 allowing proper lighting within the flies up to the Grid.

Constant circuits and all branch circuits were fused in a magazine panel (not shown here) located behind the Switchboard.  The panel contained 500 Edison plug fuses.

Two Board outlets were non switched, left the Hot Pocket and center the Test Receptacle.  The cover for the female miniature pin connector  "Miniature Outlets" is shown to the left of the Hot Pocket. 

The Fox Switchboard contained 120 dimmer control levers (exclusive of master handles) to operate the 200 resistance dimmers, ranging in capacity from 275 to 3,680 watts, the largest capacity ever manufactured.  Dimmers were wired to interrupt  the neutral side of each circuits.  For the many large loads, multiple dimmers were mechanically ganged to a single control lever (right). The dimmer plates were of two types, single or dual rating.  

Because resistance plates had to be minimum-loaded in order to dim out completely, dual-rated plates were utilized for floor pockets for example and had a typical range from 1500 to 3000 watts, allowing leeway for portable lighting devices.  If the wattage of a device did not reach the minimum, a ghost load or dummy load was added to the circuit, a lamp of the required wattage positioned at an off-stage location. Hinged cleanout doors on the underside of the floor pockets provided an easy cable route to the basement for dummies or ghosts.  Hub boards utilized Ward Leonard dimmers, and Hub's chief competitor Frank Adams used those made by Cutler-Hammer.

Dimmer control handles (left) could be interlocked into a Master control handle (center) by rotating the dimmer handle a quarter turn clockwise.  The Masters could be locked into either the top or bottom of the Slow Motion Wheel (right) by turning the handle to either left or right of center.  Thus Masters locked to the top of the wheel could cross fade with those locked to the bottom.   The fastest possible complete Board Fade on the Wheel (35 revolutions) equaled a fifteen count.  Any dimmer or Master could be left unlocked.  Board tracking sheets were complicated, to say the least.

There were ten Master Interlock transmission trains.

Every dimmer was controlled by a 15 amp capacity Pilot Switch, which activated its circuit's high amperage contactor (magnetically-held relay) in the Power Room located below the Board, and each contactor was equipped with two holding coils to allow for presetting.  Line current proceeded in a path through the Lock Switch (Grand Master), Stage or House Blackout switches, Stage or House Mains, Color Master, then to the Pilot Switch.


Each pilot switch and Color Master could be preset to any two of four choices, A or Independent, and  B or C.   Controls set to "Independent" bypassed the Mains, but not the Blackout Switch.  A and B and C selections were controlled by their appropriate Mains, and C with its small tumbler switch was generally used as a rehearsal setting.  Mains could be set to "Extended Control" and thus controlled remotely by any household type switch, such as a practical wall switch within a stage set.


Single coil Contactors for the A B and C Stage Mains (left) and one of four banks of Contactors (right).  The largest Contactors were rated for 120 amps. 

The Atlanta Fox Theatre Hub Switchboard.  The Atlanta Fox was the last Super Deluxe Movie Palace ever constructed.
1974 photo by Floyd Jillson
Part II: Audio and Electro-Mechanicals  http://backstagefox1929.blogspot.com/2014/03/part-ii-audio-and-electro-mechanicals.html

Part III: Talking Picture Projection
http://backstagefox1929.blogspot.com/2014/03/part-iii-talking-picture-projection.html