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Switches the input to modulator card 2 (Channel 2) to the CH2 VIDEO
input.
These commands are used for BITE testing.
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L. Video Signal Generator Status Request Command
Format: @BIT?<CR>
Requests the status of the modulator channel 2 input (BITE ON or OFF).
Response from VMU:
&BION<CR> Channel 2 input is VSG input.
&BOFF<CR> Channel 2 input is CH2 VIDEO.
&ERR Ø<CR> Parity error in the @BION<CR> VSG
command (see I. above.)
M. VSCU-VMU Communication Characteristics
(1) Any command from the VSCU to the VMU is normally only sent once,
unless an error is detected by the VSCU.
(2) The status request command is normally sent by the VSCU after
sending any command.
(3) Any error message is sent from the VMU only if a status request
message is received and an error condition exists.
(4) The VSCU will normally try to recover from an error by sending a
command again up to 3 times. If the VMU does not respond correctly
after 3 times, it is reported (to the CMT) as a fault or failure.
(5) The VMU does not send any message unless specifically requested to
do so by the VSCU. A frequency change command is automatically taken
as a status request command for that channel only, but the delete
channel command, test video commands, and video signal generator
commands do not generate a status response automatically.
(6) The VSCU does not send status request commands endlessly but will
ask for the VMU status periodically to ensure that the unit is
functioning correctly.
(7) If any status response is received from the VMU that is different
from that commanded by the VSCU, the command will be sent again up
to 3 times (see (4) above.)
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THIS PAGE IS
INTENTIONALLY
LEFT BLANK.
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TESTING AND FAULT ISOLATION - PART 1
1. General
A. This section gives the procedures for functional testing and fault
isolation of the Video Modulator Units (VMU) shown on the title page with
the RD-AX8308 VMU Tester and the VMU tester software, MD2HD256005A or
after.
Refer to the TESTING AND FAULT ISOLATION - PART 2 section for the
procedures with the RD-AX8308 VMU Tester and the MD2HD256199A VMU tester
software.
B. Do the functional testing first to find if the unit is serviceable or
must be repaired. If the unit must be repaired, the functional testing
also tells you the nature of malfunction, and you will use this data to
examine and repair the unit. You must do the functional testing again on
the repaired unit to make sure that the unit is serviceable.
C. The printed circuit card assemblies that are installed in the VMU are as
follows:
DESIGNATION FULL NAME QUANTITY
A1 card CPU card assembly 1
A2 card Modulator card assembly 12
A3 card RF power card assembly 1
A4 card Power card assembly 1
A5 card Mother card assembly 1
A6 card Fuse card assembly 1
A7 card Connector card assembly 1
A8 card Video signal generator card assembly 1
For these printed circuit card assemblies, we use their designations only
(A1 card, A2 card, etc.) as their names.
D. The wiring and schematic diagrams of the VMU are given at the end of this
section.
E. We give the IPL figure-item numbers in square brackets [ ] after the
assembly or part names as necessary. We do not give alpha-variant item
numbers if they are not shown on the IPL figures.
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F. Special Terms and Abbreviations
In this section, we will use the terms and abbreviations given below:
TERM DEFINITION
OMM TZZX830800 Operation and Maintenance Manual for RD-AX8308 VMU Tester.
Tester RD-AX8308 VMU Tester.
Tester program VMU tester program.
PC Personal computer you use with the tester.
Key One of the keys on the keyboard connected to the PC.
PC's screen Display screen of the VGA color monitor connected to the PC.
UUT VMU under test.
VMU Video modulator unit in general.
VMU tuner RD-AX8308-01 VMU Tuner or its equivalent.
Type (verb) Put alphanumeric characters into the PC from its keyboard.
The typed characters are shown in italics. You must use the
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COMPONENT MAINTENANCE MANUAL Video Modulator Unit (VMU)(25)
