Chapter 5 273
Troubleshooting the IF Section
Troubleshooting the A15 Motherboard Assembly
AUX_VIDEO Auxiliary Video A detected video signal (0 — 2 V) that has passed
through the video filters. No amplitude corrections
have been applied to this signal. A voltage divider
at J16, AUX VIDEO OUTPUT, reduces the signal
amplitude to 0 — 1 V.
BW5 Bandwidth 5 A bias voltage that activates either the LC or
crystal bandwidth-filter mode.
BW6 Bandwidth 6 Controls the crystal-filter bandwidth.
BW7 Bandwidth 7 Controls the LC filter bandwidth.
COUNT_IF Counterlock IF A buffered 21.4 MHz IF signal from the output of
the A13 bandwidth filter assembly to A25
Counter-Lock assembly.
CRD_ANLG_1 Card Cage Analog
1
An analog signal from assemblies installed in the
card cage to the A16 input multiplexer. When it is
selected, the signal passes through the A16
video-filter and peak-detector sections. It is
available on AUX_VIDEO after it passes through
the video filter.
CRD_ANLG_2 Card Cage Analog
2
An analog signal from assemblies installed in the
card cage. The signal goes directly to A16 A/D
conversion section, bypassing both the video-filter
and peak-detector sections.
DCOM Digital Common A common ground for all digital circuitry.
DISCRIM or
DISCRIMINAT
OR
Discriminator For Spans ≤10 MHz, the A25 Counter-Lock
assembly sends a dc tuning voltagethrough the A16
Processor/Video assembly to the A7 Analog
Interface assembly. The A7 assembly then adjusts
the YTO to reduce residual FM.
EXT_HSWP External High
Sweep
EXT_HSWP performs two functions: 1) It provides
external control of high sweep on the A16
Processor/Video when an external signal is
connected to J15, HIGH SWEEP INPUT/OUTPUT.
2) It provides the HSWP signal as a rear-panel
output at J15, HIGH SWEEP INPUT/OUTPUT.
This is an open-collector signal. It should never be
driven high.
FAN FAN +12 V power supply for the B1 fan.
WRUP High Power Up Enables the initial start-up sequence for the CPU
on the A16 Processor/Video assembly when the
analyzer is first turned on. This occurs prior to the
start-up of other related assemblies.
Table 5-6 A15 Motherboard Mnemonic Descriptions (Continued)
Mnemonic Full Name Description
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