Vor/Loc Converter I/O Board - Honeywell Bendix/King KX 165A Maintenance Manual

BENDIX/KING
29), COLDATA (P2011-27), and COLDATA (P2011-25). These signals are routed directly to the
display connector (J2012). ROWDATA (P2011-22) and ROWCLOCK (P2011-20) are buffered by
U2009-A and U2009-B respectively. The buffered signals are level shifted from 5V/GND to -178V/
-190V by Q2002 and Q2003. The level shifted signals are buffered by U2003-A, U2003-B, and
U2003-C. The buffered signals then go to the display connector J2012. DISPEN (P2011-23) is
level shifted from 5V/GND to -178V/-190V by Q2004. The level shifted signal is then fed to the
display connector. LUMCTRL (P2011-9) is a voltage level between 0.4VDC and 1.9VDC that is
used in conjunction with the duty cycle of DISPEN to control the brightness of the display. LUM-
CTRL is fed through to the display connector (J2012-16).
-190VDC (P2011-1,3) is sent to the display connector and is used to generate two more voltage
levels. -178V is generated using zener diode CR2001. The -190V is pre-regulated to approxi-
mately -95V by Q2005 and then the -95V is regulated to -80V by U2014. The -178V and the -80V
are fed to the display connector J2012.
RBSCLK (P2011-21) and RSP3* (P2011-6) are used to clock U2011 and U2012. U2011 and
U2012 are parallel to serial shift registers that are chained together. The inputs to U2011 and
U2012 are tied to the pushbuttons, push-pull switches, and the optical INC/DEC switches. The
state of the inputs are shifted to the main board via SDI (P2011-16). The photocell R2040 is fed
to the main board via FOTOCELL (P2011-14). DS2001, DS2002, DS2003, DS2004, DS2005,
and DS2006 are the bulbs used to backlight the front panel. LIGHT_GND (P2011-12,19) is always
tied to ground in the lighting bus. 14V/LGND (P2011-8,11) is connected to the lighting bus if a
14V lighting bus is in use and is left open if using a 28V lighting bus. 28V/LGND (P2011-10,13)
is tied to the lighting bus if a 28V lighting bus is being used and is tied to ground if a 14V lighting
bus is used.
The power switch is connected to the front panel via E18 (PWRSW) and E17 (PSWLO). PWRSW
is fed to the main board via P2011-7 and PSWLO is fed to the main board via P2011-15. The
COM volume pot is connected to the front panel at E19 (COM HI), E20 (COM WIPER), and E5
(COM LO). The COM volume pot connections are fed to the main board connector P2011 and
the setting is read by an A to D converter on the main board processor. The COM volume is then
controlled by setting digital pots on the main board. The NAV volume pot is connected to the front
panel at E12 (NAV HI), E13 (NAV WIPER), and E14 (NAV LO). The NAV volume pot connections
are fed to the main board connector P2011 and the setting is read by an A to D converter on the
main board processor. The NAV volume is then controlled by setting digital pots on the main
board.
4.3.8

VOR/LOC Converter I/O Board

Refer to figure 6-26 for VOR/LOC Converter I/O board schematic.
4.3.8.1 OBS resolver interface
A 30 hertz analog signal from the main board is applied to buffer amplifier U7-C. The output of
this Buffer Amplifier drives the rotor of the Indicator OBS resolver. Returning from the indicator,
are the three stators of the OBS resolver. Stators E and G are connected to the Voltage reference
board output. Sine and Cosine stators D and F are each connected to low pass active filters con-
sisting of U7-B, R23, R26, R30, C38 and C36, and U7-D, R24, R27, R32, C39 and C37 respec-
tively. These filters are anti-aliasing filters required by the Analog to Digital Converter contained
on the Main Board. The main board samples these signals and calculates the setting of the OBS.
4.3.8.2 D-Bar driver
The D-Bar output of the converter is produced by continuously updating the setting of the digital
pot U1-A to correspond to the required D-bar offset as determined by the VOR/LOC converter soft-
ware in the main processor. The update rate is about 15 Hz. The voltage at the wiper of this digital
pot is filtered with a RC time constant of about 0.84 seconds. The +RIGHT and +LEFT outputs
Page 4-44 15610M00.RCD
KX 165A
Rev 0, Jun/2000