BENDIXKing KY 96A, Maintenance Manual

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B
KY 96A, KY 97A
Rev 5, Apr 2003 MM 006-05674-0005.dwd Page 4-10
The display is a liquid crystal (LCD) type with three sections (“USE,” “STBY,” and
“CHAN”). The “USE” frequency, which is the active frequency, is displayed in the
“USE” window at all times. A standby frequency, which can be exchanged with the
“USE” frequency, is displayed in the “STBY” window when in standby entry mode.
When in channel or program mode, the channel frequency is displayed in the “STBY”
window and the channel number is displayed in the “CHAN” window. When in channel
mode the letters “CH” are displayed between the “CHAN” and “STBY” windows. When
in program mode the letters “PG” are displayed to the left of the “STBY” window. The
letters “TX” are displayed to the right of the “USE” window during transmit.
The uP I702 sends a 112 bit serial stream through pin 10 to pin 1 of I801 (LCD driver)
on the display board. The serial stream contains backplane/ mode and segment infor-
mation. Each bit is clocked through pin 11 of the uP I702.
The LCD display viewing angle is controlled by the bias provided by I801 to the dis-
play. The output of the voltage divider formed by R755, R801, and R802 is applied to
the base of Q803. The collector of Q803 is connected to +5 Vdc, and the emitter is
connected to I801 pin 12 which provides I801 with a reference voltage, which sets the
bias level applied to the display by I801.
The display brightness is controlled in three different ways, dimming through the air-
craft 14 or 28 Vdc lighting bus or half brightness all the time.
When the aircraft 14 Vdc lighting dimmer bus is selected, pins 7 and 9 of I702 are low
and pin 8 of I702 is high. This turns on Q704 thereby pulling E705 low which supplies
a ground to 3 of the 6 light bulbs for the LCD display backlighting. Q705 is off allowing
the 14 Vdc lighting voltage to pass through CR703 to E704 to 14 Vdc across
two sets of 3 light bulbs in series for the LCD display backlighting.
When the aircraft 14 Vdc Max lighting option is selected, pin 9 of I702 is low and pins
7 and 8 of I702 are high. This causes Q704 and Q705 to be on, placing E704 at
ground and E704 at +14 Vdc.
When the aircraft 28 Vdc lighting dimmer bus is selected, pin 7, 8, and 9 of I702 are
low. This causes Q709 to be on, placing E705 at +28 Vdc.
When the aircraft 28 Vdc Max lighting is selected, pins 7 and 8 of I702 are low and pin
9 of I702 is high. This causes Q702 to be on and Q709 to be on thereby pulling line
E705 to +28 Vdc.
4.3.6 Audio Amplifier Board
The audio amplifier board consists of a summing amplifier and a 4 watt/ 8 watt ampli-
fier.
I1201A and associated parts form the summing amplifier. Three 500 ohm auxiliary in-
puts are loaded by R1201, R1202, and R1203. The summing amplifier reduces the