5.4 TROUBLESHOOTING GUIDE
Table 5-4 provides a general troubleshooting chart for use by a technician to isolate circuitry failures to
specific functional areas within the VHF radio.
1
NOTE
Miiponents within the radio are generally not field replaceable. Therefore repairs to the
radio typically go down to the PC board level only.
A replacement parts iii for the VHF 5200
can be found in Section 6.
r
I
Item Number
Symptom Possible Cause
Unit does not turn on
a. Defective power switch
b. IOamp. Fuse in power line open
1
c. Diode
Dll
open
d. Noise filter
L15
open
e. Capacitor Cl19 and Cl20 shorted
f. Defective regulator
IC7(5v)
No sound with AF signal
a. Defective internal speaker
2
applied to pins 1 and 2 of
b. Defective
IC5
and/or associated
IC6 components
3
No sound with AF signal
a. Defective volume control
applied to volume control b. Defective mute circuitry
(IC201)
Squelch circuit
a. Check squelch control
4
inoperative
(b.
Defective
IC4and
/or associated circuitry
between pins 7 and 9
No receive (Rx) a. Defective regulators
IC7(5V)
b. Defective
QlB(RX
B+)
c Check IC4 audio output voltage at pin 9
d.
Defective AF amplifier
Q21
e. Defective mute circuitry
IC201
5
f.
Check XLT2 output for 21.145 MHz signal
g. Check 21 .GMHz output of first mixer
QIQ
h. Check 216MHz output of ceramic filter IF amplifier FILI
i.
Check 21 .GMHz output of first IF amplifier Q20
j. Check 455KHz signal from ceramic filter
FlL2
k. Failure of VCO circuit
(Q4,Q3,
and/or PLL IC3)
I.
Defective CPU
(IC201)
Low receiver sensitivity
a. Check antenna and connector for possible
corrosion or bad connection
6
b.
Failure of the output from
Q17,
QIQ,
QZO,
and/or
IC4
c. Check the output level of
VCO per
para.
5.3.1
Table 54 TROUBLESHOOTING CHART
25
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