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TM 11-5820-890-30-5
4-9.
OPERATIONAL CHECK. Continued
Step 3. AUDIO AMPLIFIER CHECK FOR AM-7239/VRC AND AM-7239B/VRC.
Action
Response
a. Set RESPONSE: OFF.
Set CAL:
FCTN GEN:
FREQ: 1 kHz (900 to 1100 Hz)
LEVEL: 15 V p-p (14 to 16 V p-p)
FCTN: SINE.
Set CAL:
OFF.
Set LOAD: 4.
Set STIMULUS: 7.
Set RESPONSE: 1.
Set RESP SEL: S2. Read scope.
b. Disconnect cable at J5 and move it to J3.
Read scope.
c. Set RESPONSE: 2. Read scope.
d. Disconnect cable at SCOPE CH A and test
adapter SCOPE 1. Connect X10 probe to
SCOPE CH A. Attach mini probe tip adapter
to SCOPE 1 on test adapter. Insert X10
probe tip into mini probe tip adapter.
Set LOAD: 1.
Set RESPONSE: 3. Read scope.
e. Set PTT: UUT. Read scope.
f. Set PTT: OFF.
g. Disconnect cable at J3 and move it to J5.
h. Set PTT: UUT. Read scope.
i. Set PTT: OFF.
j. Disconnect cable at J5 and move it to J4.
Set LOAD: 4.
Set RESPONSE: 2. Read scope.
k. Disconnect cable at J4 and move it to J2.
Read scope.
l. Set RESPONSE: 1. Read scope.
m. Set RESPONSE: 3.
Set LOAD: 1. Read scope.
a. Scope reading is 13 to 19 V p-p. If no
signal is present, go to chart 11. If a
signal is present but not correct, the
audio amplifier (5A2) is bad.
b. Same response as for step 3 a. If not,
connector 5A3J3 is bad.
c. Scope reading is less than 1.4 V p-p.
If not, the audio amplifier (5A2) is bad.
d. Scope reading is 60 to 78 V p-p. If no
signal is present, go to chart 12. If a
signal is present but not correct, the
audio amplifier (5A2) is bad.
e. Scope reading is less than 0.5 V p-p. If
response is same as step 3 d, go to chart
13. If not, the audio amplifier (5A2) is bad.
f. No response.
g. No response.
h. Same response as for step 3 e. If not, the
wire from 5A3J3-C to 5A3J5-C, or connec-
tor 5A3J5, is bad.
i. No response.
j. Scope reading is 13 to 19 V p-p. If no
signal is present, go to chart 14. If not,
the audio amplifier (5A2) is bad.
k. Same response as for step 3 j. If not,
connector 5A3J2 is bad.
l. Scope reading is less than 1.4 V p-p.
If not, the audio amplifier (5A2) is bad.
m. Scope reading is 60 to 75 V p-p. If not, the
audio amplifier (5A2) is bad.
4-9
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