Item Number
Symptom
Possible Cause
CPU inoperative
7
a. Turn off the power once, and try again
b. Check CPU clock frequencies (pins 22 and 23, and
pins 26 and 27 of
c. If clock frequency is not present, check for
line
8
Display malfunction
a. Check the interconnection to the LCD display
b. Inoperative CPU
No transmit (TX)
9
1 0
1 1
1 2
a. Defective
switch
b. Defective regulators
c. Defective
+B)
d. Check power transmit circuit
ICI)
e. Failure
circuit (Q4 and /or Q3) or PLL IC3
f. Check PLL control voltage for 3.5 VDC at
on
channel 60.
g. Failure of talk detection circuit
Low RF power output
a. Check RF power output from
. If it checks
good, check the triple Pi type network components
and antenna switching diode
(D4). If not good then check the voltage level
outputs of the drive amplifiers Qland Q2 as well as
the associated circuitry
b.
Check
power control circuit
and
Poor or no modulation
a.
output frequency at pin 14 of PLL IC3
PLL phase detector output at pin 12 of PLL
and
associated circuitry
b. Check 12.8 MHz crystal
PLL output frequency or level
incorrect
a. Check frequency of 12.8 MHz
b. Check the frequency input at pin
of IC3 and
the transmit frequency
Table 54 (Continued)
26
