36
Table 54 (Continued)
Item
Number
Symptom Possible cause
9 No transmit(TX) a. Defective PTT switch
. Defective regulators IC15 (5V), IC17
(8V)
c. Defective Q32 (TX +B)
d. Check power transmit circuit (Q3, Q4,
IC1)
. Failure of VCO circuit (Q15 and/or
Q17) or PLL (IC9)
. Check PLL control voltage for 3.5
VDC at TP1 or channel 16
. Failure of talk detection circuit (Q9)
[CPU AF Board]
10 Low RF power output a. Check RF power output from IC1. If
t checks good, check the triple P type
etwork component (L1, L2, C3, etc.)
nd antenna switching diode (D2). If not
ood then check the voltage level
utputs of the drive amplifiers Q3 and
Q4 as well the associated circuitry
b. Check power control circuit (Q1, Q2,
Q5) and IC2
11 Poor or no modulation
. Check VCO output frequency at pin8
f PLL10. PLL phase detector output at
pin 5 of PLL IC9a associated circuitry
b. Check 12.8MHz crystal (XTAL1)
12 PLL output frequency or
incorrect
a. Check frequency
f 12.8MHz crystal
(XTAL1)
. Check the frequency input at pin 8 or
IC9 and verify the transmit frequency
