R E P L A C E M E N T S
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.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.
(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.
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.
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
[COVER] [REGISTRY] [TITLE PAGE] [CONTENTS] [INTRODUCTION - PAGE 1] [STORAGE BATTERIES - PAGE 9] [STARTING AND TESTING - PAGE 14] [SETTING UP - PAGE 20] [REHEARSING - PAGE 27] [TROUBLES - PAGE 29] [REPLACEMENTS - PAGE 34]