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If the filaments of the tubes and the exciter lamps fail to light, while the plate voltages check O.K., the indication is that a fuse in the 15 volt generator circuit is burned out. Check the 60 ampere fuses at the back of the panel and the 60 ampere fuse in the low voltage fuse box at the M-G set.

If the filaments do not light and the plate voltages are very low, or give no reading at all, the indication is that a fuse in the 250 volt generator circuit is burned out. Before checking the fuses, make certain that the M-G set is running. If it is running and no readings are obtained, stop the M-G set and check the 10 ampere fuse in the 250 volt line at the back of the rack (See Figure 116) and the 20 ampere 250 volt fuse in the low voltage fuse box at the M-G set.

If the volume level of the loudspeakers drops to a very low value, check the two 5 ampere loudspeaker field fuses at the back of the panel (See Figure 116).

If the storage battery ammeter fails to indicate either charge or discharge when the low voltage generator field rheostat is manipulated, the indication is that one of the 60 ampere fuses at the back of the panel is burned out. If it is found that this is not the case, the trouble will probably be in the reverse current relay, in which case the RCA service man should be notified. If the battery ammeter fails to show charge or discharge, a noticeable amount of hum is liable to be produced in the loudspeakers.

For a further discussion of the troubles which may be experienced with this equipment, see Chapter XIV.

178. General Description of the PG-2 Equipment. -The Type PG-2 is a motor-generator operated large theatre equipment. An equipment of this type includes the following apparatus:-Type PS-1 sound heads, Type PT-2 turntables, one Type PA-5 amplifier rack, Type PL-11 loudspeakers, a four unit motor-generator set, and one pair of Type XCR-19 Exide storage batteries. The power output of the amplifier is slightly less than that of the Type PA-1 used in PG-1 equipments.

The amplifier has four panels, exclusive of the compensator panel which is usually mounted on the top of the rack as shown in Figures 117 and 118. The top panel of the rack proper is the voltage amplifier panel. The second panel from the top and the bottom panel are power amplifier panels, and the panel between the two power amplifier panels is the control panel. A small panel with six snap switches is usually mounted on the side of the rack. This panel is a loudspeaker switching panel, and is not illustrated in the figures.

Only one voltage amplifier unit is used with this equipment. Two power amplifiers in two separate units are used together.

179. Description of the PA-5 Voltage Amplifier Panel. -This panel, which is the voltage amplifier, a relay fader, projector indicator pilot lamps, exciter lamp rheostats, a test meter, six metering jacks and a phonograph pick-up jack.


Chapter Thirteen Pages
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