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This is the Rectifier Room at Projection level. There are four Hewettic rectifiers in two groups of two. Each unit is continuously rated for 100 Amps at 100 Volts. The gap between numbers 2 and 3 is for rear access. There is a contactor panel to the right. There was originally a lantern light above, now boarded over. The chains on the doors are supposedly for health and safety reasons. |
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This is the rear view behind one of the rectifiers
clearly showing the glass rectifier bottle which contains mercury. There
are six lobes off the bottle, containing electrodes. The Mercury
rests on another electrode under the bottle. To start up the unit, an external
electromagnet causes a sprung contact to dip into the mercury pool, causing
an arc to strike. This vapourises the mercury and the sustaining arc is
then struck. A large transformer beneath changes three phase mains to six
phase current which is then rectified by the mercury vapour to provide
the projection feeds. A large fan keeps the air flowing over the transformer
and rectifier
bottle, the blade of which can just be seen. |
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This is the Grid, 60' above the stage. The Fly tower is about 70' wide and 24' deep. This is the view from the external access door on the side lane, the right hand wall being the proscenium. The Counterweight system has been dismantled but some of the steel wire rope remain in-situ, although not under tension. Most of the sets had four grid pulleys and a header pulley at the far wall above the counterweight frame. |
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The pulleys for the safety curtain can be seen on the proscenium wall, this being the third header pulley closest to the hoist. A slack rope detector can be seen to the right, which appears to be the safety curtain release rope. The detector is to ensure that the hoist only operates whilst the brake is activated. |
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This is the hauling engine to lift the safety Curtain. This is just to the right of the above photograph. The Safety Curtain counterweights are below the unit on the Stage Right Proscenium wall. The spring below the drum is connected to the release lever, the actuating rope travelling across the grid and down to the release panel in the Prompt Corner, stage left. The significance of Number 3 is unclear- Knights also provided mechanisms for the Orchestra Pit, Organ Lift, Act Drop, Tabs and Magnascope. It would appear that there is no hauling rope- instead the counterweight ropes pass over a sheath in the style of a lift mechanism. The winch handle can also be seen for raising the curtain manually in the event of a fault or power cut. |
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This is the remains of the counterweight frame onstage beyond
the false wall of screen four, stage left. Each Set was counterweighted by a cradle which travelled vertically between stage and grid level. The vertical slotted steel are the rear cradle guides, the front guides having been dismantled. A thick sisal rope was connected above and below the cradle via pulleys forming a loop. The handles below operate the rope locks, locking off the set at the desired height. Counterweights were loaded onto the cradles from the loading Gallery about 50' above, the grid height being 60' above the stage. |
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This is the ammeter in the projection room above the rewind
bench. The arc current was 120 Amps for each of the Victoria 8s and dust marks on the glass in that location indicate this is where the meter spent most of it's time when the Theatre was open, apart from change-overs, intervals or when a Lime or Slide Lantern was in use. There was also a Voltmeter on the left-hand Box wall above the non-sync, however that permanently showed 50 volts, even when the rectifiers were off! |
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We are now in the Prompt Corner stage left. Beyond the plasterboard
wall to the right is the edge of the Proscenium and screen 4.To the left
of the Plasterboard is the back of the vertical girder that forms the Safety
Curtain guide
channel. The large
control with the two large red buttons is for the safety curtain. To release
it,
the
right
hand
red
button
is pressed which releases the brake. The Safety Curtain is designed to
start descending with the brake released, being sufficiently out of balance
to overcome friction without crashing down in an uncontrolled manner. As
the Iron approaches stage level, a damper mechanism slows it down sufficiently
to come to rest gently on the stage, a fabric pouch on the leading edge
forming a smoke seal. To raise the curtain again, the long black handle
is pulled down to latch the brake and the raise button is pressed to operate
the winch. The second control is for the sparge pipe- intended to douse
the Iron with water to keep it cool and prevent it buckling in the event
of a fire. |
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This is round the corner of the Proscenium. The reset handles
for the Iron & Douser can be faintly seen on the right. Other
controls in this area are for Act Drop, Tabs and a Buzzer to alert the
Box. Miscellaneous switches were for backstage rehearsal lighting. Six
2Amp mains sockets are actually for Microphones. There also used to be
a loudspeaker down here as a crude foldback system to the stage & box. |
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This is the Stage Lighting Switchboard in the Prompt corner.
The original Major system was replaced circa 1953, in order to be able
to operate shows without an electrician on-stage. It is a much cruder system
than the original, having no interlocking of dimmers. Each dimmer handle
can be screwed down onto the common shaft and then raised or lowered collectively
by turning the shaft master wheel at the far end. The board provided for
the 24 FOH Pageants, Footlights, three Battens and various Dip Traps used
for
Wing
Flood Towers
and sundry Focus Lanterns. It has been partially dismantled by the Operators
to re-use the dimmers in the motorised units. |
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The control switches to the top left of the Board. As well
as Master Switches (which worked Contactors in the room below) there are
also switches for the Board Light and Batten Pilots (extra lamps in the
battens for scene change & sundry use). The board is based around the three-colour
variety colours of Amber, Red and Blue (although the Amber shaft is coloured
white). This Board was made by F H Pride, who also made one
of the two Stelmars. The
original
stage
lighting
installation was by Major. |
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This unit is a motorised dimmer which originally controlled the 24 FOH Pageants in the Circle front enclosure, actually Major 500W Focus Lanterns. After the tripling, it was used to control a number of Patt. 123 Fresnels located on the drop wall as the balcony front enclosures were partially obscured. It now controls a number of four way floodlights used to light scrren 4 as Footlights upstairs.Four ganged 3kW dimmers fade up or down under control of buttons in the Box and on the switchboard. This unit is located in the corner next to the Switchboard Master controls. Similar and larger units are located in the Contactor room below for the motorised Footlights and House Lights (no longer in use). |
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This is behind the switchboard. On the floor can be seen a large number of counterweights removed from the Frames. The tall thin door was originally the access to the rear of the Major Switchboard from the Pass Door Corridor, now the only access into this closed off area and technical time capsule. |
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This is behind the switchboard where it can be seen where the dimmers have been removed to use as spares in the motorised sets over the years. (They have generally been overloaded so have progressively burnt out). |
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This is the main fan for the plenum system. The safety guard is a modern innovation, the belts originally being exposed. The fan is an impellor design, sucking air from the centre and blowing it downwards and to the right into the main air feeder duct. This duct runs under the Orchestra Pit towards the rear stalls, also feeding towards two vertical riser shafts either side of the theatre to deliver fresh air at roof level through ceiling ducts. A third shaft feeds air to the Front Of House areas, including decorative grilles incorporated into the Circle Lounge light fittings. |
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The vertical column is actually an air shaft fed from a fan at Dressing Room roof level. This cools a number of resistances behind the grilles towards the bottom. The regulator handle moves a wiper across a number of studs, varying the resistance in-circuit and therefore the speed of the fan. The studs are visible to the operator through the small glazed window above the actuator. The box below is an isolator unit. Beyond the controller the edge of short wooden steps can just be seen- that leads up to the motor and an access hatch into the air shaft. |
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A view of the original Carrier refrigeration system. This huge motor drove the large flywheel which worked the compressor, circulating ammonia through the system. A similar 1930s plant with two compressors was still in use at Nottingham Ice Rink in the early 90s, although it used the Ammonia to chill brine (salted water) via calorifers in a secondary circulatory system. |
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The evaporators for the refrigeration plant located in the Plenum room, directly equivalent to the pipes on the back of your Fridge that get warm. The original plans show this assembly at roof level of the dressing room block, however they actually became additional rooms as-built. |
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The centralised vacuum plant in a small room under the stage. The dust collection box is to the left, the motor centre and the suction fan to the right. |
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A view of the main intake room power distribution system.
Hidden Busbars feed the various oil filled isolators, which connect to
cables that distribute onwards throughout the building (seen below). |
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Here is a view of the two Stelmars at the far right of the
Box. The one with a vertical colour change arrangement at the back is a
Brockliss Stelmar and was located on the right, next to the Master Brenograph
(which was removed to make way for the Cinemation Console). The other Stelmar
had tracker wire colour change made by F H Pride, and was located on the
left next to the Non-Sync. Bill Furness modified the unit so that it was
possible to gauge how well the arc was burning from the front of the lantern,
as feeding the arc was by hand from knobs on the rear. The Brockliss one
had a motorised feed and needed much less attention. Both units were perfectly
balanced and stayed where they were left. |
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The Slide Lantern, which was located on the extreme right
of the Box, is now mouldering away in the Rectifier Room. As far as I recall,
it used 30 Amp low intensity arcs, the same as the Stelmars. Because it
was only used for short periods it tended to get the dog-ends of carbons.
The doorway leads back into the Resistance Room. |
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A view of the original Box, showing the non-rewind system.
The non-sync turntable can just be seen at the bottom left. |
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Another view of the original Box, note the Voltmeter on the
far wall. After the Victoria 8s were converted to Xenon they were fitted
with
with local regulators and the Rectifiers fell into near-disuse. |
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