The RT self-test is performed at several levels. When the FCTN switch is set to TST, the control module begins
the self-test routines. The RT receive path, ECCM module, data rate adapter, fill routing module, and audio/data
I/O module are checked. A test line to the SYSTEM connector is activated. This allows the RT to report the results
of SNAP self-tests. A self-test of the remote control modules can be performed separately.
a. Display Checks. E d should be the first display when the FCTN switch is set to TST, the control
module checks for the presence of the ECCM module and the data rate adapter. The ECCM module grounds the
FH HERE-N line. The data rate adapter grounds the DATA MODULE PRESENT-N line. See figure FO-8.
If either module is absent, its letter in the display is replaced by a dash (-).
The next display is 88888. It permits checking of the display segments. The SIG display can also be checked
during self-test. All display segments are lit sequentially with 9 remaining lit.
b. Receive Path Test (FAIL 1). The receive path is tested in four steps. First, the control module performs
a memory check (RAM and ROM). Second, the control module checks the TONE SQUELCH line. It should be at
logic 0 since there is no received signal. Third, the receive path is checked at eight frequencies in the SC mode.
See figure FO-8. The 150-Hz tone is sent from the switching module (FM MOD) to the exciter/power amplifier.
The exciter/power amplifier uses the 150-Hz tone to modulate its 3.9-MHz output. The harmonics from the 3.9
MHz are used as the test frequencies. The tuner/mixer and synthesizer are stepped through eight frequencies.
The 150-Hz squelch tone presence is checked at each frequency. Because the tuner/mixer and synthesizer have
several bands, it is possible that only one or two frequencies will fail. The last step repeats the receive path
checks for two frequencies in the FH mode.
There are secondary displays for each failed test. They will be displayed when any keyboard button is pressed
while the FCTN switch is being set to TST. They are:
Control module RAM
Control module ROM
150-Hz detect line stuck at logic 1
Receive at 78.0 MHz, SC
Receive at 66.3 MHz, SC
Receive at 58.5 MHz, SC
Receive at 50.7 MHz, SC
Receive at 46.8 MHz, SC
Receive at 39.0 MHz, SC
Receive at 35.1 MHz, SC
Receive at 31.2 MHz, SC
Receive at 78.0 MHz, FH
Receive at 35.1 MHz, FH