543 Master Caution Annunciator Power Schematic
Feb 01/74 Figure 2 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 33-15-0 Page 5
3. System Indicator Lights
A. The majority of the system indicator lights on the various modules throughout the control cabin are composed of a light cap, two bulbs and a base with two diodes, a fuse and a momentary switch. Pressing the light cap operates the momentary switch which causes the light to illuminate (push-to-test). The annunciator is easily relamped after pulling the light cap assembly from the base.
B. Two types of lights are used, one is a ground seeking type which requires a ground controlled circuit to turn it on; the other is a power seeking type which requires a power controlled circuit to turn it on (Fig. 3). The majority of the lights are of the ground seeking type. A few lights contain only one bulb and no diodes , and are not connected to the master caution circuits; however, they are operated by the master dim and test circuits. Diodes for these lights are usually in annunciation and dimming module M469. Refer to the Wiring Diagram Manual for specific circuit details of each system.
4. Annunciation and Dimming Module
A. The annunciation and dimming module consists of three printed circuit cards, a transistor circuit and diodes mounted within a box. Two electrical connectors are on the side of the box and a mounting plate is on the front. The module is installed with screws on the left side of the control stand P9 panel. Card A3 contains diodes which isolate individual system control of the system master caution annunciators from the master caution lights and provide diodes for various systems indicator light circuits. Cards A1 and A2 contain transistor circuits with zener diodes which cause certain system indicator lights to dim when the master dim and test switch is operated. The separate transistor circuit and zener diode is connected to the master caution lights and causes the master caution lights and system master caution annunciator to dim.
Master Dim Module
A. The master dim module consists of a printed circuit card with a relay, diodes and a transistor circuit. The card is installed in a card rack in load control center P6. The relay connects zener diodes and resistors in the light dimming circuits to the P5-4 ac systems generator and APU module and to the P5-10 air conditioning module. The diodes provide isolation between dual power sources for the master dim and test circuits. The transistor circuit is not used.
543
33-15-0 Page 6 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Feb 01/75
543 Typical System Indicator Light Circuit
Feb 01/75 Figure 3 33-15-0
Page 7
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
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