An extensive self-test diagnostic routine is also initi-
ated in the VIR-32 NAV receiver by pushing the TEST
switch on the NAV control unit. The NAV control unit will
modulate the active and preset display intensity from
minimum to maximum to annunciate the self-test is in
progress. If a fault condition existed prior to actuating
self-test, the NAV control unit will display the diagnostic
code associated with the fault for approximately 2 sec-
onds immediately after the TEST switch is pressed (the
code will appear in the preset display). If a fault is de-
tected during self-test, that fault code will also be dis-
played on the NAV control unit along with the word
DIAG, FLAG, or four dashes (----) in the active display.
The four dashes will be displayed along with the code 00
indicating that no faults have been found. FLAG will be
displayed along with a 2-digit code when something is
abnormal but a failure has not occurred (i.e. low signal,
etc.). DIAG is displayed along with a code to indicate a
failure has been detected in the VIR-32. Completion of
self-test is indicated when either the normal frequency
displays or a fault code is displayed on the NAV control.
A partial list of diagnostic and fault codes is provided be-
low. The codes are listed in table 7 (The TEST switch
must be pushed before any fault code can be displayed).
3-25. ADF RECEIVER (ADF-60).
a. Introduction. The ADF receiver (fig. 3-25), pro-
vides aural reception of signals from a selected ground
station and indicates relative bearing to that station. The
ground station must be within the frequency range of 190
to 1749.5 kHz. The ADF receiver has three functional
modes of operation. In the antenna (ANT) mode the ADF
receiver functions as an aural receiver, providing only an
aural output of the received signal. In automatic direction
finder (ADF) mode it functions as an automatic direction
finder receiver in which relative bearing to the station is
presented on an associated bearing indicator, and an
aural output of the received signal is provided. The tone
(TONE) mode provides a 1000-Hz aural output tone
when a signal is being received to identify keyed continu-
ous wave (CW) signals. The ADF receiver is powered
through a 2-ampere circuit breaker placarded ADF, lo-
cated on the overhead circuit breaker panel (fig. 2-7).
b. ADF Control Unit Operating Controls, Indicators,
and Functions. All operating controls for the ADF receiv-
er are located on the ADF control unit (fig. 3-25).
(1) Active frequency display. The active frequen-
cy (frequency to which the ADF receiver is tuned) and
diagnostic messages are displayed in the upper window.
(2) Transfer/memory switch. This switch is a
3-position spring-loaded toggle switch placarded XFR/
MEM, which, when held to the XFR position, causes the
preset frequency to be transferred up to the active dis-
play and the ADF receiver to be returned. The previously
active frequency will become the new preset frequency
and will be displayed in the lower window. When this
switch is held to the MEM position, one of the four
stacked memory frequencies will be loaded into the pre-
set display. Successive pushes will cycle the four
memory frequencies through the display.
(3) Store switch. This switch, placarded STO, al-
lows up to four preset frequencies to be selected and
entered into the control units memory. After presetting
the frequency to be stored, push the STO switch. The
upper window displays the channel number of available
memory (CH 1 through CH 4); the lower window contin-
ues to display the frequency to be stored. For approxi-
mately 5 seconds, the MEM switch may be used to
advance through the channel numbers without changing
the preset display. Push the STO switch a second time
to commit the preset frequency to memory in the selected
location. After approximately 5 seconds, the control will
return to normal operation.
(4) Tuning knobs. Two concentric tuning knobs
control the preset or active frequency displays. The larg-
er knob changes the 1,000s and 100s kHz digit. The
smaller knob changes the 10s, units, and tenths kHz
digits. Each detent of the larger knob changes the fre-
quency in the display in 100-kHz steps. Each detent of
the smaller knob changes the frequency in the display in
1-kHz steps, with the exception that the first two detent
positions following a change in rotational direction of the
knob will cause a 0.5 kHz change in frequency. Rapid
rotation of the smaller knob will cause frequency
changes greater than 1-kHz as a function of rate of rota-
tion. Frequencies roll over at the upper and lower limits.
The two tuning knobs are independent of each other in
that the upper and lower limit rollover of the 10-kHz digit
will not cause the 100-kHz digit to change.
(5) Active switch. The active switch, placarded
ACT, enables the tuning knobs to directly tune the ADF
receiver when depressed and held for two seconds. The
bottom window will display dashes and the upper window
will continue to display the active frequency. Pushing the
ACT switch a second time will return the control unit to
the normal two-display mode.
(6) Test switch. This switch, placarded TEST, initi-
ates the receiver self-test diagnostic routine (Self-test is
active only when the TEST switch is pressed).
(7) Light sensor. This built-in light sensor auto-
matically controls display brightness.
(8) Volume control. The volume control is concen-
tric with the power and mode switch.