曝光台 注意防骗
网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者
operates as modulator channel 1. The video channel 1 input is
selected if the RL CONT signal is low (0V). The test video input is
selected if the RL CONT signal is high (+5V). A1IC102 controls
A1IC114 (voltage regulator) to give the RL CONT signal.
Page 11
Feb 20/2002
Matsushita Avionics Systems Corporation
COMPONENT MAINTENANCE MANUAL
PART NUMBER RD-AA5002 SERIES
23-32-47
(6) A1IC102 gives the TG CONT signal to the A8 card. This signal
controls the video input to the A2 card that operates as modulator
channel 2. The video channel 2 input is selected if the TG CONT
signal is high (+5V). The internal video signal (white raster) is
selected if the TG CONT signal is low (0V).
(7) Monitoring of A2 Card
(a) Each A2 card gives an LD (Lock Detect) signal to the A1 card.
A1IC102 reads these LD inputs through A1IC109 and A1IC110 (8-to-
1 data selector). When the PLL frequency synthesizer on an A2
card locks to the specified frequency, its LD signal goes low.
(b) The 12 LD inputs are pulled up to +5 V through A1RA104 and
A1RA105. Thus, if an LD signal to the A1 card does not go low,
then it shows one of three:
1 The PLL frequency synthesizer does not lock to the specified
frequency.
2 There is no related A2 card.
3 The related A2 card has a PLL-related fault.
(c) A1IC102 identifies each of the above three as a A2 card fault.
(d) Each LD line is monitored at all times. If an LD line stays
high, A2IC102 will try to reprogram the related PLL frequency
synthesizer at regular intervals.
(8) Control of A2 Card RF Outputs
(a) A1IC102 controls the RF output of each A2 card with the power
control signals. These signals are applied through A1IC111 and
A1IC112 (hex inverters), after which they become PC01 thru PC12
signals. One PC line connects to each A2 card.
(b) The A2 card RF output is enabled when the related PC signal is
high, and disabled when the related PC signal is low (0V).
A1IC102 disables the A2 card's RF output if its LD signal is
high. This condition occurs:
1 When the power is first applied to the VMU.
2 Until the PLL frequency synthesizer is locked to the
specified frequency.
3 When the LD signal from the A2 card stays or becomes high.
Page 12
Feb 20/2002
Matsushita Avionics Systems Corporation
COMPONENT MAINTENANCE MANUAL
PART NUMBER RD-AA5002 SERIES
23-32-47
(9) All inputs and outputs of the A1 card has EMI filters.
(10) Power Backup
A1C124 (0.047 F capacitor) will keep A1IC102 powered for
approximately 200 ms if the power to the VMU is stopped. Thus, no
programming of the PLL frequency synthesizers occurs, but the VMU
continues its operation when the power is reapplied. If the power
to the VMU is stopped for more than 200 ms, the +5V power line
voltage is decreased and A1IC101 (voltage detector) applies a reset
to A1IC102. If this occurs, A1IC102 makes programming of the PLL
frequency synthesizers when the power is reapplied.
Pin 2 output (reset) of A1IC113 (voltage regulator) goes low as soon
as a power interruption occurs. This output connects to pins 2 and
33 (IRQ and PD2) of A1IC102 for power interrupt detection and
internal processing.
(11) Frequency Programming
(a) The frequency data of all modulator channels is stored in
A1IC103 (EEPROM). A1IC102 uses the stored frequency data to
program the PLL frequency synthesizers at the time when the
power is applied to the VMU.
(b) If the frequency of a modulator channel is changed from the
VSCU, A1IC102 will write the new frequency value to A1IC103 and
program the PLL frequency synthesizer of that channel.
Page 13
Feb 20/2002
Matsushita Avionics Systems Corporation
COMPONENT MAINTENANCE MANUAL
PART NUMBER RD-AA5002 SERIES
23-32-47
D. Modulator Card Assembly (A2)
There are twelve A2 cards installed in the VMU. Refer to Figure 4 for a
block diagram of the A2 card. Refer to the schematic diagram given at
the end of the TESTING AND FAULT ISOLATION - PART 1 section for full
circuit data. In the text that follows and Figure 4, the prefix "A2" for
the equipment designators is not shown for simplicity.
(1) Video Modulator
The baseband video signal (composite color) from the CN201 connector
is applied to IC202 (RF modulator) through IC201 (video amplifier)
and VR201. IC202 generates a 59.75-MHz picture carrier and
modulates its amplitude with the baseband video input. VR201
adjusts the modulation depth. Since the video input is AC-coupled,
the clamp circuit in IC202 restores the DC component before
amplitude modulation.
The A2 card is a 50-W input type if R201 and R202 are installed, and
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：
COMPONENT MAINTENANCE MANUAL Video Modulator Unit (VMU)(19)
