Motorola ASTRO Digital Saber - Page 101

10-19
Chart 30 . VHF/UHF/800MHz Receiver RF
Bad SINAD
Bad 20Db Quieting
No Recovered Audio
Spray or Inject 1st IF into
XTAL Filter
FL1.
Audio
Heard?
Is
circuit
from Q601 to
U401
good?
14.4MHz
at ABACUS
(U401) pin
15?
Check 2nd LO
Cntrl Voltage
at R413
Inject RF
into J2
IF Signal
at L605?
RF
Signal
at T1 (VHF/
UHF), T202
(800MHz)
?
RF
Signal
at L8 (VHF/
UHF), L180
(800MHz)
?
RF
Signal
at L6 (VHF/
UHF), L201
(800MHz)
?
RF
Signal at
CR109 (VHF/
UHF), CR102
(800MHz)
?
Check harmonic filter L126-127,
ant. switch, CR109, J2 contact
(VHF/UHF). CR102, L105, L103,
L106, C101, C114 (800MHz)
Program filter to
schematic test freqs.
and check varactor
voltages.
If voltages OK check
varactor filter. If voltages not
OK, check U102. Check
also Q108, R115, U102
voltages. Check U102 can
be selected by MCU
before replacing U102.
Before replacing U401 check 2nd
VCO Q1. Check VCO O/P level;
C408, C425. Disconnect R416 and
verify that a 0.5V to 5V ctrl voltage
VCO will sweep about the IF freq.
Trace IF signal
from L605 to
Q601.
Check for bad
XTAL filter.
VCO
Locked?
1st LO
O/P OK?
Locked?
Check FGU
Chart C.31 -
VHF/UHF
C.32 -
800MHz
Check Mixer,
U2, T1 (VHF/UHF).
U205, T202
(800MHz)
Replace bad
components.
Check filter between
U1 and U2 (VHF/UHF).
U202, U205 (800MHz)
Check U1 Stage.
U202 (800MHz)
Check U201 filter.
Before replacing U401,
check U401 voltages.
Check for no Rx audio
VOCON flowchart C.29.
Q601
Collector
OK?
IF signal
present?
2.1Mhz
Check
at Pin 19
U401?
Check FGU,
Chart C.31 - VHF/
UHF C.32 -
800MHz
Activity
On U401
Sel Pin?
Check J1. If
OK, Check "No Rx
Audio" Chart C.29
YES NO
NO
NO
NO
YES
YES
YES
NO
NO
YES
YES
NO
YES
YES
NO
NO
YES
YES
YES
NO
NO OR
WEAK RF
YES
VHF
UHF
800MHz
YES
NO
NO
NOTE: INJECT MODULATED
ON CARRIER FREQUENCY
SIGNAL AS REQUIRED
MAEPF-24386-O
IF FREQS:
45.15 VHF
73.35 UHF/800MHz
Check
for
3.0VDC
Check Q601
bias Circuitry
for Faults.
Check R601,
R602
NO
YES
Check U401voltages
and programming &
14.4MHz VCO
components.
Rotate Freq. Knob
Chart 31 . VHF/UHF Frequency Generation Unit (FGU)
FGU No Lo Injection/TX
Unlock
Check continuity
between:
U204-2 & J401-9,
U204-3 & J401-10,
U204-4 & J401-14.
If no fault found
replace U204.
YES
MAEPF-24389-A
NO
VDC at
VCTRL (TP5),
<0.7V?
Replace
U204
5V at
U204
Pin 11, 20, 23
25, 42?
VDC at
U204 Pin 21,
28(Tx), 29(Rx)
38 & 39
OK?
13V at
U204
Pin 36?
2.1 MHz
at U204
Pin 10?
VDC at
CR205 Pin 4
OK?
2.5V at
U204
Pin 6 & 7?
Go to VCO TX/RX
Unlock
Troubleshooting
Chart C.33.
Check CR205,
CR206, C266, C267,
C284 & C285(V),
C282, C259
VDC at
U202 Pin 1,
2 & 8 OK?
Replace
U202
16.8 MHz
at U204
Pin 14?
2.5V at
U204
Pin 14?
Check C256,
C257, C258 &
CR204
Replace
U204
16.8 MHz
at U203
Pin 10?
Replace
U204
Check Connection
at C274, R221(V),
R222(U)
Replace
U203
IC PIN VOLTAGE
U202 1, 2
8
5V
7.5V
U204 21
28
28
29
29
39
39
38
38
1.6V
1.7V (VHF TX)
1.6V (UHF TX)
1.8V (VHF RX)
1.6V (UHF RX)
4.5V (TX)
0.7V (RX)
4.5V (HIGH END)
0V (LOW END)
CR205 4 -7.5V (HIGH END)
0V (LOW END)
No 2.1 MHz
NO
YES NO
NO
YES
YES
YES
NO
YES
YES NO
YES
YES
NO
YES
NO
OK
YES
NO