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RF Section
A12 Switched Barium-Tuned Mixer (SBTX)
A12 Switched Barium-Tuned Mixer (SBTX)
The RF diagnostics routine in the adjustment/diagnostic software is
recommended for troubleshooting faults in and around A12. The RF
diagnostics will prompt you where to connect a source and another
spectrum analyzer to make RF signal level measurements.
A test board, part number 08564-69201, is connected between the A7
LOMA and A10/A12 RYTHM/SBTX ribbon cables, and the A14
frequency control assembly. DC measurements are made using the
TAM manual probe cable on several test connectors on the test board.
An 3478A DVM is used to measure the voltage across A14R91 (the
large power resistor next to A14Q404) to determine the tuning current
in the A12 preselector.
Be sure to follow all prompts precisely; failure to do so will result in
incorrect fault determinations.
Chapter 12
609
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