Tandy Radio Shack Realistic PRO-2021 User manual

I ~EALI.s::C®
IervIce
PRO-2021
PROGRAMMABLE SCANNER
AM /FM MONITOR RECEIVER
Catalog Nurnber: 20-113
CUSTOM MANUFACTURED FOR RADIO SHACK. A DIVISION OF TANDY CORPORATION

CONTENTS
Page
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
BLOCK DIAGRAM .... 00 •••••••••••••••••••••••••• 0 ••••• 0 0 ••• 0••••• •••• ••• ••••• 4
PRINCIPLES OF OPERATION 0" ., ••• , • o' o.o o' 0 .0 ••••••••• 0" •• •• •• •• •• • • 5
GENERAL OPERATION OUTLINE 00.0 ••••••• 0" • 0" 0 0 o' o. .. .. .. . . . . .. .. 7
ALlGNMENT 0 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 8
RECEPTION CHECK 0
•••••• 0 • • • • • • • • • • • • • • • • • • • • • • • • • • • •• 14
MEMORY CHECK 00.00 •••••• 0 0 ••••• 0' ••••• ••••• •••• •••• •• 15
TROUBLESHOOTING o0 ••• 0 •••••••••••• 0 •••• 0 ••••••• 0 •••••• 0•••••• •• •••••• •• 16
PoC. BOARD (TOP AND BOTTOM VIEWS) ... 0 0 0 •••• 000 ••••• 0 •• 0 •••• 0 0" ••• • •••• •• •• 18
WI RING
DIAGRAM o' 0 •••• 0 ••••• 0 ••••••••••••••••• 0 0 • • • • • • • • • • • • • • •• 20
ELECTRICAL PARTS LIST 0 •••• 0 • 000 ••••••••••• 0 •• 0 • 0 •• 0 • 0 0 • 0 • • • • • • • • • • • •• 21
DISASSEMBLY /EXPLODED VIEW o .. 0 •••••• 0 •••• 0 •• 0 •• 0 ••••• 0 • 0 • 0 0 •••• 0 0 • • • • • • •• 32
MECHANICAL PARTS LIST. 0 0 ••••• 0 ••••••••••••••••• 0 •••••••••••• 0 0 •• 0 0 0 • 0 0 •• o' 33
SEMICONDUCTOR LEAD IDENTIFICATION AND IC CIRCUIT DIAGRAM .. 0 0 0 •••••••• "34
MICROPROCESSOR (IC) PORT
FORMAT 0 •••••••• 0 ••••• , ••••••••••••••••••••••• 0.. 42
APPENDIX 0 ••• 0 •••••••• 0 0 ••••••••••••••• o' 0 0 • • • • • • • • • • • • • •• 43
SCHEMATIC DIAGRAM , .. 0 ••••• 0 ••• 0 0 ••••••••••• 0.0.... •• •• • • • • •••••• 44
PRODUCT SAFETY NOTICE
Many electrical and mechanical parts in this chassis have special characteristics. These character-
istics often pass unnoticed and the protection afforded by them cannot necessarily be obtained
by using replacement components rated for higher voltage, wattage, etc. Replacement parts
that
have these special safety characteristics are identified in this manual and its supplements;
electrical components having such features are identified
bya b:. in the schematic diagram and
the parts list.
Before replacing any of these components, read
the parts Ustin this manual carefully. The use
of substitute replacement parts
that do not have the same safety characteristics as specified in
the parts list may create shock, fire or
other hazards.

Description
Frequency Coverage
VHF LOW (or MID*)
AIRCRAFT
VHF HIGH
UHF
Sensitivity (20 dB SIN)
FM: 3 kHz DEV. at 1 kHz
AM: 60% MOD. at 1 kHz
VHF LOW (or MID*) FM
AIRCRAFT AM
VHF HIGH FM
UHF FM
Selectivity -6 dB
-50 dB
Spurious Rejection
at 40 MHz (or 78 MHz*)
at 120 MHz
at 154 MHz
at 450 MHz
(except primary image)
IF Rejection 10.7 MHz
at 154 MHz
Modulation Acceptance
(EIA RS-204-A)
Signal to Noise Ratio
VHF LOW (or MID*)
AIRCRAFT
VHF HIGH
UHF
Residual Noise (Vol. Min.)
Scanning Rate Fast
Slow
Search Rate Fast
Slow
Priority Sampling
Scan Delay Time
Audio Output Power
(T.H.D. 10 %)
SPECI FICATIONS
Nominal spec,
0.5pV
2.0 pV
1.0pV
1.0 pV
±9 kHz
±15 kHz
50 dB
50 dB
50 dB
60 dB
±8 kHz
45 dB
35 dB
45 dB
35 dB
3mV
8 channels/sec.
4 channels/sec.
8steps/sec.
4steps/sec.
2 sec.
2 sec.
1.5 W
Limit spec.
30 ~ 54 MHz 5 kHz steps
*or 68 - 88 MHz 5 kHz steps
108 - 136 MHz 25 kHz steps
138 - 174 MHz 5 kHz steps
380 - 512 MHz 12.5 kHz steps
2pV
5pV
3pV
4pV
±12 kHz
±18 kHz
40 dB
40 dB
40 dB
Not specified
40 dB
±5 kHz
30 dB
25 dB
30 dB
25 dB
5mV
6 - 10 channels/sec.
3 - 5 channels/sec.
6 - 10 steps/sec.
3 - 5 steps/sec.
1 - 3 steps.
1 - 3 sec.
1.0 W
Channels of Operation
Channel, Frequency and Mode
Display
Receiving System
Power Source
Tape Out
Speaker
Accessory
Dimensions
Weight
Any 200 channels in any band combination
Liqu id crystal display
Direct Key entry Digital Frequency Controlled Synthesizer,
Superheterodyne lst IF: 10.7 MHz 2nd IF: 455 kHz
AC 120V, 60 Hz, 15W max.
DC 13.8V, 8W
2=10 kohm, 500 mV nominal, 300 mV limit
Built-in 3" (77mm) 8 ohm Dynamic Speaker
Telescopic antenna Approx. 24-13/16" (63cm)
Car mounting bracket with screws and DC cable
Approx. 3-1/8" x 10-2/8" x 8" (80 x 260 x 200 mm) HWD
4.4 Ibs (2.0 kg)
NOTE: Normnet specs reptesent the design specs: all units should be able to approx trnete these -- some wil! exceed and some
may drop slightly below these specs. Limit specs represent the absolute worst condition that still might be conski-
ered acceptable; in no case should a unit perform to less than within any limit spec.
* VHF MlD range (68 - 88 MHz) is for Europeen and Australian Models onlv,
-3-

BLoeK DIAGRAM
IANTI
~ OSC,MIXER,IFAMP- kj
VHF RF AMP MIX IF AMP
~
CRYSTAL
-(LOW, AIR,
Hl)
014 FILTER OUADRATURE DET
01,2,3 01"-10,57
XF-I
NOISE AMP
VRI
IC-2
ISOUELCH!
UHF RF AMP MIX
~
....-....
011"" 13
04,5
AM IF AMP OET &tANL
AM/FM SW
I--
I-
-&SO
015,16
024,25
.--i
IC3,5(3/6)
017 VR2
VCO(LOW) BUFFER
~
014,15 AMP
f-- I--
IVOLUME I
,...
06
07
/
/
/
(
1:~
I
I
VCO(AIR, Hl,
TRIPLER IIHEADPHON
~
UHF) 017
'-
ZEROMATIC AUDIO
016 &KEY TONE AMP I
09
I--
08
IC5,6 020,21
IC-9
!4ä
6V
lISPEAKERI
(I
I
UHF AIR IITAPE OUT1
I
Hl LOW
,. ____ J
EL DRIVER f f f t/
/
T15, Q30 /
/
BAND SELECT VOLTAGE /
MEMORY
IC-8 REGULATOR
....f.
RECTIFIER
--0
IC-12 ..........-0
""0---'
043
I010,11,12,13
IC-4
SW2 ACI20V
EL-I
f
(240V)
~
CPU
VOLTAGE
CPU PRESCALER
KEYBOARD
r---
IC-11 IC-I
!4" CONTROL REGULATOR
~
'-
018,19 026
IC-IO
1tI1
5V
LOW BATT
PLL
-- LOW-PASS OC-DC CONV
LCD DET L., FILTER -
025,26
027,28,29
IC-7
f----
022,23,24 036,37
IBACK upi
tBATT
SWI
IRESET swi
-4-

PRINCIPLES OF OPERATION
The PRO-2021 is a PLL (Phase Locked Loop) Synthesized VHF/UHF AM/FM Receiver, controlled by a
CPU (Central Processing
Unit) via the keyboard.
The
VHF Low Band (30 - 54 MHz) or Mid Band (68 - 88 MHz) and High Band (138 ~ 174 MHz) are
received in 5 kHz increments.
Aircraft Band (108 - 136 MHz) is set up for 25 kHz increments, and the
UHF Band (380 - 512 MHz)
for 12.5 kHz increments.
Receiving frequency range, frequency determination, scanning speed, delay time, etc.. are all functions
controlled by the CPU. The CPU is able
to do only the assigned functions, and no modification of the CPU
is feasible.
The
following paragraphs explain the operation of the circuit in terms of the functional blocks:
Avaractor (variabie capacitance diode) tuning ("Automatic Tuning System") is employed on all Bands.
Field-effect transistors (FET) are used in the
RF/MIX circuits of Low (Mid). High and Aircraft Bands, to
achieve
optimum mix-modulation and mutual-modulation characteristics.
014 amplifies the 10.7 MHz IF.
A 10.7 MHz
monolithic Crystal Filter is incorporated for better selectivity.
IC-2 contains the Local Oscillator, Mixer, IF
Amplifier, Ouadrature FM Detector, Noise Amplifier and
DC amplifier. A Crystal Oscillator praduces 10.245 MHz, which mixed
with 10.7 MHz, resulting in 455
kHz IF. A 455 kHz Ceramic filter is pravided to increase selectivitv, The 455 kHz IF is amplified in the IF
Amp stage, and a Ouadrature FM Detector detects it to an audio signa!. A portion of the 455 kHz Ceramic
Filter output is picked up, amplified and detected by the AM IF Amp. which consists of 015 and 016
and is then applied to the next stagevia the AN L circuit.
Detected output of AM and FM is applied to IC-9. IC-9 amplifies audio signals and feeds them to the
speaker.
The zeromatic
circuit consists of IC-5 and IC-6 and 020, 21 and functions in the search mode.
IC-11 is the CPU. The CPU does data processing, calculation, etc.
Any unstable supply voltage (VDD) to the
CPU can praduce CPU malfunctions, such aswrang data processing, wrong data transfer, etc.
To overcome
this C149 and R146
"initialize" the CPU. Initialization is done when RESET switch is pushed. Figure A
shows
initializing waveform.
The CPU contains
two clocks. One produces the waveform shown in Fig. Bat Pins 49 and 50, which is used
for program functioning. The other waveform, which appears at Pins 3 and 4, is derived from X-3 (32.768
kHz)
which is used to determine Delay time, LCD display, etc. (Shown in Fig. Cl.
IC7 is the
PLL frequency synthesizer. The VCO output is 1/64 or 1/65 divided by Pre-scaler IC1. The
output of Pin 15 and 16 of IC7 is applied to the VCO contral via the Low Pass Filter (022, 23, 24).
-5-

5V---
1.5V
OV---
0.8sec ..I
Figure A
5V --
OV --
IC 11
50 49
/
R147
IC152
Figure B
-6-
D47
IC 11
4
X3
C154
1
C153r
Figure C

Turn POWER SW ON.
Automatically set to SCAN
mode, and starts scanning
when the sa i. on.
GENERAL OPERATION OUTLINE
Press IPROGRAM Ito set to
Program mode.
I
Press IMANUALI.
When
fMANDAD IS pressed
again the ehan"el advanees.
To select one of 1 - 200
ehannels, push the number
key and then push
IMANUALI.
When battery voltage drops
LOW BATT indicates and
beep-tone sounds trom
speaker.
Key in search frequency as
follows:
Press ~ and key in
lower frequency
with numeral
keys.
Press
~.
Press [QM!!J and key in
upper frequency.
Press IENTI.
Press ill to search from
lower frequency. Press
~
10 seareh trom uppër fre·
ouencv.
(Squelch must be on.)
Press IMONI to
store the
desired frequency (10 monitor
cnannets) in the seareh mode.
-7-
Command the de.ored fre·
Quency
In each ehannel as
follows:
Key in
the desired frequency
with numeral Keys.
Press IENT I to memoroze the
frequency.
If wrong frequency (out of
!he
band I is entered. it dis·
plays
"Error".
Press lillA[J to c1ear
"Error".
Press [jiijQ(ffiAMl.
Advances to next channel.
Key in the frequency and
press IENT I. repeat it to
memorize frequencies one by
one.
Press I?~~~ to set to scan
Channel 1- 200 when squetch .... --4 ...
is on. Use ILOCK OUT Ito
skip undestred channels.
Press :SPE E:Q] to set to hIgh
speed scan, press 19a,n 10
revert to
normal speed.
Far prior uv operanon. set as
follows:
First press IPROGRAM
land
channel numeral kevs.
Press !PRIORITYI to start tne
ononrv tunetion. aPRIORI·
TY INII1 appel' on the dIsplay.
Press \!RIo RITY ito clear
onontv.

ALIGNMENT
ALlGNMENT AND TEST POl NTS
TC3 TB
®~
TC6
®~T7
T3 TI T2
~~~
TC4
®
T6 T4 T5 TC2
~ ~~~TPI
0----- o--!-- TP2
~ TC5~ I
T9 ~~
~TP5
TI3
~
Til
~
TI2
~
TIO
~
TP4
TP3
ALlGNMENT PREPARATION
Test equipment required
1. Oscilloscope (0 - 500 kHz, 0 - 50 MHz)
2. AC SSVM
3. DC SSVM
4. Frequency
Counter (200 MHz)
5. 8-ohm
dummy load
6.
Slow Sweep Generator with variabie marker
(10.7 MHz)
7.
VHF Sweep Generator with variabie marker
(30 - 54 MHz,
108 - 174 MHz)
8.
UHF Sweep Generator with variabie marker
(380 -
512 MHz)
9. FM Signal Generator
(30 - 54 MHz,
108 - 174 MHz, 380 - 512 MHz)
10.
AM Signal Generator (108 - 136 MHz)
NaTE1: Use non-metallic tuning tools.
The test
equipment and Receiver should be warmed up at least 30 minutes before proceeding
with alignment.
Input signal from the Generator should be kept as low aspossible and still obtain usabIe output.
NaTE 2: Three silver oxide batteries are required to hold the memory when main battery is disconnected.
Always be sure the unit is loaded with fresh batteries or the pre-programmed channels wil! be lost
(end
wil! have to be re-programmed).
NaTE 3: For servicing VHF Mid band of European/Australian modeIs, see Appendix on page 43.
-8-

IF SECTION ALlGNMENT
Step 1: Conneet instruments as shown below.
3.8 -4.2V p.p
T
+15kHz
SCOPE
TP·3
UNIT
UNDER TEST
10.7 MHz
L-ilé----lSWEEP GENERATOR
001uF
TP1
-15kHz
INPUT 100~JV
Step 2: Adjust T10 for maximum output so that the 455 kHz marker is in the center of the discrimi-
nator curve and for best linearity, as shown above.
During alignment, maintain Sweep Generator
output at the lowest level possible to prevent
overloading.
VCO ALlGNMENT
Step 3:
Step 4:
Step 5:
VHF la BAND
Step 1: Connect a DC SSVM to TP5 and ground.
Step 2: Program CH1, 2 and 3 asfollows:
CH1 (30 MHz), CH2 (40 MHz), CH3 (54 MHz).
Select Channel 3 (54 MHz) and adjust TC3
for 13V on the DC SSVM.
Select Channel 1 (30 MHz) and adjust T7
for 1.0V on the DC SSVM.
Repeat steps3 and 4
until no improvement is observed. The DC SSVM should read as below.
30 MHz Voltage at TP5 0.9 - 1.0V
40 MHz Voltage at TP5 4.1 -
4.5V
54 MHz Voltage at TP5 12.5-13.1V
REFERENCE FREQUENCY osc AlIGNMENT
Step 1: Connect Frequency Counter to 07 Collector through a ceramic eapacity (47 - 100 pF) and
ground.
Step 2: Select Channel 2 (40 MHz) and observe vca Frequency.
Step 3: Adjust TC6 so
that the frequency is 50.700 MHz ±20 Hz.
Step 4: Repeat
VHF la BAND vca AlIGNMENT.
AI RCRAFT Hl BAND AND UHF BAND
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Connect a DC SSVM to TP-5 and ground.
Program CH1, 2, and 3 - 9 asfollows:
CH1 (108 MHz), CH2 (380 MHz), CH3 (138 MHz), CH4 (120 MHz), CH5 (150 MHz), CH6 (450
MHz), CH7 (136 MHz), CH8 (174 MHz), CH9 (512 MHz).
Select Channel9 (512 MHz) and adjust TC4
for 13V on the DC SSVM.
Select Channel 1 (108 MHz) and adjust T8
for 1.0V on the DC SSVM.
Repeat steps3 and 4
until no improvement is observed. The DC SSVM should read as below.
108 MHz Voltage at TP5 0.9 - 1.1V
380 MHz Voltage at TP5 1.2 - 2.0V
138 MHz Voltage at TP5 1.8 - 2.5V
120 MHz Voltage at TP5 2.2 -
3.0V
150 MHz Voltage at TP5 3.7 - 4.7V
450 MHz Voltage at TP5 5.5 -
6.6V
136 MHz Voltage at TP5 5.6 - 6.5V
174 MHz Voltage at TP5 9.8 - 11.0V
512MHz Voltage at TP5 12.5-13.1V
-9-

RF AMP ALlGNMENT
VHF LO BAND
Step 1: Conneet instruments as shown below.
SCOPE
UNIT
UNDER TEST
SWEEP
GENERATOR
30MHz -54MHz
Step 2:
Step 3:
Step 4:
Program 30 MHz (CH1), 40 MHz (CH2) and 54 MHz (CH3).
Select Channel 2 (40 MHz) and adjust T3 and T6 asshown below RF waveform.
Check Channels 1 through 3 for the below RF waveform. Aslight deviation as shown below is
acceptable.
jij
~
0
w
-3
ti)
z
0
-6
Q.
ti)
w
tI:
30 40
FREQIMHzl
54
Step 2:
Step 3:
Step 4:
AI RCRAFT BAND
Step 1: Connect instruments: Same conneetion as VHF Lo band except Sweep Generator frequency,
change to 108 MHz to 174 MHz.
Program 108 MHz (CH1), 127 MHz (CH2), 136 MHz (CH3)
Select Channel 2 (127 MHz) and adjust Tl and T4 for maximum RF waveform.
Check Channels 1 through 3 for maximum RF waveform. Slight deviation as shown below is
acceptable.
NOTE: Perform AIRCRAFT BAND RF AMP ALlGNMENT before VHF-Hl BAND.
If this procedure is not followed, alignment may be impossible and/or inaccurate.
0
jij
~
W
lil
-3
z
0
Q.
lil
W
a:
108 127
FREQIMHz)
-10-
136

Step 2:
Step 3:
Step 4:
VHF-Hl BAND
138 MHz (CH1), 154 MHz (CH2), 174 MHz (CH3)
Step 1: Connect instruments: Same conneetion as VHF Lo band except Sweep Generator frequencv,
change to 138 MHz to 174 MHz.
Program 138 MHz (CH1), 154 MHz (CH2), 174 MHz (CH3L
Select Channel2 (154 MHz) and adjust T2 and T5 for maximum RF waveform.
Check Channels 1 through 3 for maximum RF waveform. Slight deviation as shown below is
acceptable.
0
êii
~
UJ
-6
'"
z
0
c,
'"
UJ
ex:
138
UHF BAND
Step 1: Conneet instruments as shown below.
154
FREOIMHz)
174
ANT. JACK
UNIT
UNDER TEST
SWEEP GENERATOR
380MHz - 512MHz
Step 2:
Step 3:
Step 4:
Program 380 MHz (CH1), 450 MHz (CH2) and 512 MHz (CH3).
Select Channel 1 (380 MHz) and adjust TC1 and TC2 as shown below.
Check Channels 1 - 3 for the below RF waveform at each frequency marker. Aslight deviation
asshown below is acceptable.
êii
0
~
UJ
-6
'"
z
0
<l.
'"
UJ
ex:
380
450
FREOIMHz)
- 11 -
512

ZEROMATIC FUNCTION AND HOW TO CHECK IT
IC512/ 6 )
030
~el
DiscrillljllgfOr curve
(Zeromatic functions when OUTPUT is in "H" level.)
83
e2
0< el <
e3
e] < el < e2e2< el < VCC
OUTPUT (ICS Pin No. 10) LHL
To adjust el voltage, receive signal in Manual mode, and set T10 to obtain 2.8V (1/2VCC) at TP-3. It is
convenient
to usethe National Weather Service Signal for the adjustment.
In the event Zeromatic does
not function correctly, refer to "REFERENCE FREQUENCY OSC ALiGN-
MENT" and check 50.700 MHz ±20 Hz, and adjust T10 again at 2.8V DC while a Signal is being received.
-12 -

I
.. I
I
KEYS ACCESS PULSE OUTPUT(lC11)
I
I-
I
I
P30-W Lr-
P31---,---.J,....------------------~
P32~ ~
P33-L.....J ~
P40-L.....J ~
P41-L.....J ~
P42 -L.....J I r--
P43 . I---'
-a...J W
P50 :LJ :~
P51---LD W
P52~ ~
P70~ U-
I I I
IIi
I I I
iiI
I I I
2001ls~ t-I
I 1
---.j 400 I--
IIlS I
NOTE: Usea signal at Pin 66 of IC11 astrigger, and then observe the keys access pulse when
IPROGRAMI key is pressed.
PLL DATA WAVEFORM(lC11)
CLOCK
(PING9)
DATA
(PINGel
SI
IS
NOTE: Enter 150.000 MHz to channel 1and loek out other channels.
Observe
the waveforms while scanning.
- 13-

Is Power Supply
circuit OK?
Is
ICll clock oscillation
wavefarm or reset OK?
Is IF
Amp or Noise
Amp circuit (IC2)
OK?
Is CPU
control circuit
OK?
IsVoltage Regulator
OK?
Is
IC", and reset
properly?
Is Keyboard
and/or
associated circuit OK?
Is IC 2
andlor
aS$Ociatedcircuit OK?
Is voltage Regulator
OK?
Is OC-OC converter
OK?
Is Band select lwhich
consistsof IC 8, Ol 0-
013) OK?
IsCPUcontrol circuit
(which consists of 018.
019.026) OK?
Is Backup
battery OK?
RECEPTION CHECK
Tabi.'
010 - 013
COLLECTOR
NOTE 1~5.5V
V
011 012
013
O~OV
FREO.
BAND
LOW or MlD 1 0 0 0
UHF 000
Hl 0010
AIR 000
NO
NO
NO
NO
NO
NO
Is memory power
supply circuit (which
consistsof IC 10) OK?
Is PLL circuit (which
consists of IC1, 7)
OK?
Is Mute circuit l017,
IC3) OK?
Is
ICll OK?
-14 -

Enter (program)
150,000 in
CHl
Disconnect AC or DC
plug and then conneet
after 2 hours.
MEMORY circuit is OK
NO
NO
NO
MEMORY CHECK
NOTE1: Prior to checking CPU Svstern. measure
supply voltage to I Cs. (See schematic
drawing.)
NOTE 2: While checking the following items, the
ICs can
"latch up". If so push RESET
switch abou tone second and then
continue.
Defective Voltage
Requlator IC
10.
Defective CPU control
circuit, 018 - 019
and/or IC 12
Defective Back-up
battery.
-15 -

TROUBLESHOOTING
Symptom
Cause/Remedy
1) Display does
not light and no 1)
Faulty power cord:
sound when POWER is on. •Replace
the power cord.
Volume Control
: MAX. 2) Defective power transformer:
Squelch Control
•Replace
the power transformer.
Counterclockvvise (CCW) 3) Defective
power switch:
•Replace the
Volume control (VR2).
4) Defective rectifier D43:
•Replace
the D43.
5) Defective voltage regulator circuit cornponents:
•Replace the
defective parts.
2) Display lights
but no sound. ,) Defective speaker or headphone jack:
Volume Control
: MAX.
•Replace
the defective parts.
Squelch
Control :CCW 2) Defective audio amplifier IC-9 and/or associated circuit components:
•Replace
the defective parts.
3)
Defective IF amplifier IC-2 and/or associated circuit components:
•Replace
the defective parts.
4)
Defective functional squelch control IC-3, IC-5 and/or associated circuit
components :
•Replace
the defective parts.
3) Sound
but display does not light. I ) IC-" is running "wild":
Volume Control :MAX
•
Activate Reset Switch.
Squelch Control
:CCW
2) Defective initiate control and/or associated circuit components.
•Replace
the defective parts.
3)
Defective IC-4 and/or associated circuit components:
•Replace
the defective parts.
4)
Defective DC-DC converter circuit components:
•Replace
the defective parts.
5)
Defective LCD:
•Replace.
6)
Defective CPU IC-" and/or associated circuit components :
•Replace
the defective parts.
7) Defective 0'8, '9, D26 and/or associated circuit cornponents:
•Replace
the defective parts.
8) Defective EL' and/or associated circuit components:
•Replace the
defective parts.
4) Does
not scan and squelch does not
') Defective functional squelch control IC-5, 017 and/or associated circuit
operate.
components:
•Replace
the defective parts.
2)
Defective IC-2 and/or associated circuit components:
•Replace
the defective parts.
3)
Defective IC-4 and/or associated circuit componerits:
•Replace
the defective parts.
f----.--- --._-
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5) Does not scan but soueten operates. 1)
Defective 017, IC-5 and/or associated circuit components:
•Replace
the defective parts.
2) IC-" is
running "wild":
•Replace Reset
Switch.
3) Defective IC-" and/or associated circuit components:
•Replace
the defective parts.
6) Scan does
not operate but
Squelch control is not adjusted correctly:
MANUAL selecter operatos. •
Adjust SOUELCH (VR-,) c1ockwise.
- '6-

Symptom Cause/Remedy
7) Display lights
but PROG RAM does Defective
Keyboard or connector and/or associated Circuit components
not operate. •Replace the defective parts.
8)
Low (Mid) band does not operate 1) Defective
Low band RF Coils T-3, 6 and/or VCO circuit components.
but Air, High and UHF operates. •Replace the defective parts.
2) Defective band
switch circuit components:
•Replace
the defective parts.
9)
Air band does not operate but
Defective AM IF Amp 015,16 and/or associared circuit components.
Low, High and UHF operate. •Replace
the defective parts.
10) High band does
not operate but
1) Defective Air and High band RF Coils T 1,2,4,5 and/or associated
Low and UHF operate. circuit cornponents:
•Replace
the defective parts.
2)
Defective band switch circuit components:
•Replace
the defective parts.
11)
UHF band does not operate but 1) Defective UHF band RF amplifier 04, mixer 05, multiplier and/or
Air, High and Low operate. associated
circuit cornponents:
•Replace the defective parts.
2)
Defective band switch circuit components:
•Replace the
detective parts.
12)
Air, High and UHF band do not
Defective VCO circuit 08, D16 and/or associated circuit components:
operate but Low operates. •Replace
tbedetective parts.
13)
All bands do not operate but
1) Defective PLL circuit I Cl, 7 and/or associated circuit components:
display OK.
•Replace
the defective parts.
2)
Defective IC-4 and/or associated circuit components:
•Replace
the defective parts.
14) Searches
but does not haIt on 1)
Defective Q21, IC-6 and/or associated circuit components:
the correcttrequencv.
•Replace the defective parts.
2)
Discriminator Coil T10 is out of adjustment:
•TP3 shall have
1/2 VCC (approx. 2.8V) in normal receiving mode.
3) Is
50.700 MHz adjusted correctly?:
•Refer
to page 9 REFERENCE FREOUENCY OSC ALIGNMENT.
- 17

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P.C. BOARDS (TOP AND BOTTOM VIEWS)
(TOP VIEW)
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