Chapter 5 275
Troubleshooting the IF Section
Troubleshooting the A15 Motherboard Assembly
LOG_LIN Log Linear Controls switching between log and linear modes on
the A14 Log Amplifier assembly.
LPWRON Low Power On The front-panel line switch provides a TTL low
when the switch is depressed. This initiates
start-up of the A8 Power Supply and A16
Processor/Video assemblies.
LTIO Low Top-box
Input/Output
Strobe line for Input/Output (I/O) data transfers.
REF_CAL Reference Cal A DAC on the A7 AnalogInterface assemblyadjusts
the gain of the A9 Third Converter assembly
through REF_CAL.
SWEEP_RAMP Sweep Ramp A 0 to +10 V ramp signal that corresponds to signal
sweep across the display. The signal is sent to J14,
SWEEP OUTPUT, on the rear frame.
VIDEO_IF Video IF The detected 21.4 MHz IF signal from the detector
on the A14 Log Amplifier assembly to the input
multiplexer on the A16 Processor/Video assembly.
VTO_TUNE Voltage-Tuned
Oscillator Tune
A tuning voltage from the A25 Counter-Lock
assembly to A9 Third Converter assembly. It locks
the 600 MHz oscillator on the A9 assembly to the
frequency reference.
Table 5-6 A15 Motherboard Mnemonic Descriptions (Continued)
Mnemonic Full Name Description
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