R E P L A C E M E N T S
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General
 While projectionists are expected to follow the instructions previously given for dealing with
equipment troubles, and to do simple repair work on the apparatus, such as soldering broken
connections, replacing burnt out tubes or burnt out fuses, tightening loose parts, replacing
defective parts by other parts supplied or recommended for the purpose by us, etc., they must
never experiment with the equipment by changing circuits or substituting coils, condensers,
etc., of other types, or by using records of types not authorized by us, as this might result in
a situation constituting default of our contract with the theatre.
Keep all spare parts in a clean, dry place; be sure that the temperature is not above 80°, as
this causes deterioration of the photo-electric cells.
Life of Vacuum Tubes
Vacuum tubes require replacement when any one of the three following conditions is noticed:
(1) When plate currents begin to fall below the minimum values specified earlier in this book.
This, of course, applies only in cases where a meter is provided on the amplifier for the
purpose of checking these currents. When two or more amplifier tubes begin to show low plate
current at the same time, the fault probably does not lie with them but may be due to the
rectifier tubes; therefore, try renewing the latter.
(2) When the tube begins to be noisy. This applies to amplifier tubes.
(3) When the filament shows one or more bright spots instead of glowing uniformly throughout
its length.
Tubes that have once been used in a rectifier are unfit for use in amplifiers, as they are incapable of giving good quality. Therefore be sure to exercise care on this point
in handling the stock of spare vacuum tubes.
Changing Receivers
If a defective receiver is found by application of the various tests described in these
instructions, replace it by one of the spares we furnish. Be sure to connect each wire to the
same terminal on the new receiver as it was connected to on the old one. All four receiver
terminals are marked for this purpose. If a receiver is connected wrongly, the quality of the
sound as heard in the house will be spoilt.
Never open receivers or attempt to repair them. Never operate a receiver without the horn, as
this may damage it.
In installations having only one horn, if this horn is provided with a receiver switching device
the spare receiver may be put in use by simply moving over the throat lever. The double-throw
switch located in the stage cut-out box, which controls the sound circuit to the receivers, must
also be thrown to the other position so as to connect in the spare receiver.
Changing Reproducers
If a defective reproducer is found by application of the various tests described in these instructions, replace it by one of the spares we furnish.
The base of the reproducer assembly (swivel, arm and reproducer unit) fits on a bracket attached
to the turntable pedestal. This base is clamped to the bracket by means of a milled thumb-screw.
When this thumbscrew is loosened and
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