If the picture has not been cued previously, it will be well to start with no compensation. This means
that the compensator dial will be turned as far as possible in a clockwise direction and will point to the
figure 40 on the dial. This compensator has been provided to compensate for lack of intelligibility due to
poor recording. If the recording consists of music only, it will be found most desirable to run with the
compensator set at 40. If, on the other hand, the recording contains speech, it may be found necessary
to lower the compensator setting. If the speech sounds "boomy" and is not intelligible, the
compensator should be reduced gradually until the speech is cleared up. Never run the compensator
lower than is absolutely necessary for intelligible reproduction. If the compensator is run at too low a
setting, the quality will be greatly impaired and the sound will be "tinny", because of a lack of volume
on low notes.
The volume control potentiometer is located on the amplifier. The volume of sound from the
loudspeaker should always be kept just as low as is consistent with intelligible reproduction. See
section 163.
223. Troubles on PG-13 Equipment. -If a bad hum develops, it is an indication that the commutators of
the generators are dirty or pitted. This can be avoided if the machines are inspected before use. See
section 37.
If the amplifier goes "dead" inspect the tubes for burned out filaments or abnormal appearance. If the
tubes appear to be in good condition they should all be replaced with tubes which are known to be in
good condition. Always keep a full set of replacement tubes ready for emergency use.
If the filaments of the tubes fail to light, while the proper voltage reading is obtained on the low voltage
meter of the motor-generator set panel, check the 12 volt generator fuses of the motor-generator set. See
Figure 36 for their location. If one of these fuses should burn out while operating, the readings of both
meters will increase appreciably.
If no sound can be obtained from the equipment even after the tubes light and have been checked and
found to be O.K., check the 600 volt fuses of the M-G set. (See Figure 36 for the location of these fuses.)
If one of these fuses should burn out during operation, "no sound" would result and the voltages of
the 12 volt and 600 volt generators would increase appreciably, especially that of the 600 volt generator. After
replacing the burned out fuse, watch the tubes carefully for abnormal appearance and inspect them for
shorts between the elements. If the plate of any tubes should become red hot stop the M-G set
immediately and replace the tube.
A further discussion of the troubles which might occur with this equipment is set forth in Chapter XIV.
Copyright 1930 RCA Photophone, Inc.
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