(b)
The rotor of synchro transmitter B4 is connected to the RDDMI heading gear train. The stator of B4 provides an alternate magnetic heading source for the navigation units.
J1
18
VOR/ADF-1 (34-28-00) 26V AC
BEARING
IN (FIG.12)
26V AC SYNCHR0 (FIG.9)
XMTR B4 BEARING-1
MAG HDG TO VALID (FIG.13)
VHF NAV UNITS (FIG.12)
23 COMMON (FIG.9)
26V AC 10
C
(FIG.9)
VOR/ADF-2 BEARING IN (FIG.12)
24
26V AC (FIG.9)
BEARING-2
+5V VALID (FIG.13)
20
LIGHTING
(34-28-00)
21 26 COMMON (FIG.9)
RDDMI SPEERY P/N 4034559-901
Radio Digital Distance Magnetic Indicator Schematic Figure 8
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A
737-300/400/500MAINTENANCE MANUAL
(6) VOR/ILS Power Distribution Schematic (Fig. 9)
(a)
The VOR/ILS navigation systems receive 28 volts dc and 115 volts ac through circuit breakers as shown in Fig. 9. System No. 1 receives power from the battery bus and the standby bus in panel P18 while system No. 2 is fed from electronic bus No. 2 in panel P6.
(b)
The 115 volts ac is stepped down to 26 volts by instrument transformers No. 1 and No. 2. This 26 volts ac is fed to the navigation units for VOR operation and to the RDDMIs for bearing pointer and heading synchro excitation.
(c)
The 28 volts dc from the G/S and VOR/LOC circuit breakers are fed to the navigation units. G/S dc powers the glide slope receiver while VOR/LOC dc powers the internal power supply, arms the ILS mode relay, and provides the ILS 28V DC mode voltage output.
(d)
The VOR/LOC dc is also fed to the VHF NAV control panel, to relays in the flight instrument accessory unit, and through the HSI VOR/ILS - NAV transfer relays to arm the auto tuning circuits in the VHF NAV control panels. 1) The VOR/LOC dc to the control panel powers the frequency
displays, the AUTO/MAN annunciators, the test and agility relays, and the manual frequency display shutter bar.
2) The VOR/LOC dc to the flight instrument accessory unit is used to energize the test inhibit, and agility relays. VOR/LOC-1 dc is also fed through the accessory unit to the instrument warning approach trigger circuit in the comparator.
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A 737-300/400/500MAINTENANCE MANUAL
NO. 1 VOR/ILS SYSTEM
VOR/ILS Power Distribution SchematicFigure 9 (Sheet 1)
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A 737-300/400/500MAINTENANCE MANUAL
NO. 2 VOR/ILS SYSTEM
VOR/ILS Power Distribution SchematicFigure 9 (Sheet 2)
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