Pll Circuit Troubleshooting Hints - Realistic trc-449 Service Manual

Check whether voltage
reading on Pin 1 of IC5 is
approx. 9.2 volts.
Yes
Defective D44,
L16 open or
poor soldering
Defective IC5,
L17 open or
poor soldering
Yes
Check whether there is
No
Saw Tooth Wave of 10 kHz
on Pin5 or 6 of IC7.
Yes
Check whether
voltage is 2 volts
on TP7 at CH1.
Check whether there is
Output of approx.
11.2850 MHz on TR40
Base.
6. PLL CIRCUIT TROUBLESHOOTING HINTS
No good
Good
PLL is not
defective
Check whether there is R F
voltage on TP8.
Check whether there is
RF output of approx.
0.5V P-P on TP6.
Check whether each Channel
Chart.
frequency indicated in Frequency
Frequency in each mode matches the
Yes
Yes
V
Check whether there is ap-
prox. 2.2 Volt reading on
TP7.
Yes
Switching Circuit, or
TR34, 38 or 39 open or
poor soldering
Defective Crystal,
soldering
Defective TR40 or
L24 or poor
Check whether 5V DC
appears on Pin2 of IC6.
Yes
Defective
Switch.
Defective
Flexible PCB
Check whether signal
of 1 thru a few MHz is
readable on Pin 11 of
IC7.
Yes
Yes
Defective IC7
Yes
Check whether BCD
programs on Pin 13 thru
21 of IC7 work as
specified in the Chart
Yes
Re-align
L17
I No
Check whether Pin 13 thru
21 of IC7 are programmed
as in the Chart.
Defective IC6
and/or 5V line.
Defective Xtal5
and/or IC7 or
poor soldering.
Check whether signal
of 1 thru a few MHz
signal is readable on
Base of TR30.
Yes
Defective F ET4
L19 open.
Defective TR30 and/or
31 or poor soldering
Defective Pin 2, 3
or 4 of IC7 or
defective TR35 or
poor soldering