12.
EXPLANATION OF EPC STEPS.
(Refer to Table 2.)
a. Steps 1 through 3 check power.
If steps 2 or 3 are good, they
indicate power present at the receiver-transmitter (RT), so a failure of
step 1 would indicate a burned out power lamp in the AM-7152. A failure of
both steps 2 and 3 while step 1 is good indicates a probable power problem
between the AM-7152 and the RT.
If steps 1 and 2 are good, a failure of
step 3 indicates a problem with the RT or handset. If the handset is the
cause, you could confirm it by turning the SPEAKER switch on and hearing
receive noise at the speaker. If no receive noise is heard at the handset
or speaker but steps 1 and 2 are good, the problem is in the RT.
b. Step 4 checks the receive signal path.
Receiver noise should be
heard in both speaker and handset. GMT time signals are broadcast on 5 MHz,
10 MHz, 15 MHz, and 20 MHz (all within the frequency spectrum of the AN/GRC-
213) at 1-minute intervals. Before deciding that step 4 is abnormal, you
should listen for at least one minute on each of these five frequencies.
Any signal heard confirms step 4 as good. When outside CONUS, this may have
to be done by using the frequency of any commercial AM radio station known
to be transmitting.
Table 3 gives a partial listing of international
stations which can be used. Try several of these stations located nearest
where you are before deciding step 4 is abnormal.
c. Step 5 checks volume adjust.
If step 5 is abnormal, the problem is
in the AM-7152 or RT-1209.
d. Step 6 checks the squelch circuit.
If step 6 is abnormal, the
problem is in the AM-7152.
e. Step 7 checks sideband switching.
If signal is clear in one
position but is not heard in the other position, the problem is in the RT.
f. Step 8 checks the keying circuit. If step 7 is
abnormal when keying
the RT from the audio jack, the problem is in
the RT or handset
(microphone).
If step 8 is normal when keyed from
the audio jack but
abnormal when keyed from an AN/VIC-1, the problem is in
the AN/VIC-1, in the
AM-7152, or in the audio cable.
g. Step 9 checks the transmit signal path and muting of the speaker.
The muting circuit is part of the AM-7152, and the transmit signal path is
carried through the handset, the RT, and the matching unit AM-6874.
h. Step 10 checks RT transmit to a distant station.
If step 10 is
abnormal and steps 1 through 9 are normal, the problem is in the RT, AM-
6874, SA-2365, or antenna system.
i. If step 11 is abnormal, the problem is in the AM-7152.
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