Back to the beginning of the Museum Web Site

S T A R T I N G   A N D   T E S T I N G

Page 18

Meter marked "Plate" should read in each case not less than 1.35 nor more than 1.55 milliamperes.

(8) On 42-A and 43-A amplifiers, each meter pointer should be on red mark.

(9) Turn on horn safety switch.

When the amplifier installed is the 46-B (Fig- 5), proceed as follows:

(1) See that horn safety switch is off.

If starting up during a show, make sure that theatre horns are turned off, by means of output key on amplifier.

(2) See that storage batteries are switched on ready for use, as covered in preceding section.

On DC supply, start motor generator.

See that power safety switch is closed.

(3) If using film reproduction, set filmdisc switch at "Film", and turn control knob on amplifier door so that adjacent meter reads 270 milliamperes.

(4) On 46-B amplifier, turn on starting switch, and adjust filament control so that right-hand meter reads 270 milliamperes.

(5) Check reading on left-hand meter on amplifier. It should be between 0-95 and 1.1 milliamperes. Reading on center meter should be between 1-3 and 1.6 milliamperes. Press meter key; right-hand meter should now read between 50 and 65 milliamperes.

(6) Turn on horn safety switch.

Testing Amplifier Equipment

Having started up the amplifier equipment as already described, test it as follows before every show in which it will be used;

(1) If both disc and film equipment is installed, switch in whichever is to be tested first, by means of the film-disc switch.

(2) Put pick-up equipment on one machine on turntable in circuit, by setting fader at point 9 on side to which this equipment is connected.

(3) If testing disc pick-up, rub needle of reproducer lightly with finger. This should be clearly heard in monitor horn.

(4) If testing film pick-up, see that lamp current is at value previously specified, and readjust if necessary. Now take out tension pad and move a card up and down across light spot. Every time this is done a click should be heard in the monitor horn. Finally, replace light gate.

(5) move fader to other side and test that pick-up equipment in the same way.
(6) Bring fader to zero.
Shutting Down Amplifier Equipment

Proceed as follows, and always in the order given here: (1) Turn off horn safety switch.

(2) Turn off starting switches on 42-A and 43-A or 46 type amplifiers.

(3) Turn off power safety switch.

On DC supply, also shut down motorgenerator set.

(4) Set film-disc transfer switch at "Off" (if installation is equipped for film reproduction).

(5) Turn off storage batteries at battery panel.

Starting Mechanism and Testing System

EVERY DAY before the house opens test the theatre horns individually and at the same time check the operation of the projector and pick-up mechanism, as will be described in this section.

Regular daily testing is of great value and importance for the reason that a large proportion of' failures and defects do not happen suddenly, but develop gradually, and hence can be detected and remedied before they become serious.

Keep a stock of two or three records or sound films especially for testing, independently of those used in the show. Piano, speech, and orchestra selections are the most suitable. At least