Chart 28. Vhf/Uhf/800 Mhz Receiver Rf - Motorola ASTRO XTS 3000 Service Manual

NOTE: INJECT MODULATED
ON CARRIER FREQUENCY
SIGNAL AS REQUIRED
YES
Inject RF
into J2
YES
IF Signal
at L605?
Trace IF signal
NO
from L605 to
Q601.
Check for bad
RF
XTAL filter.
Signal
at T1 (VHF/ YES
UHF), T202
Check FGU
(800MHz)
NO Chart C.31 -
1st LO
?
VHF/UHF
O/P OK?
C.32 -
NO Locked?
800MHz
Check Mixer,
YES
RF
U2, T1 (VHF/UHF).
Signal
U205, T202
YES
at L8 (VHF/
(800MHz)
UHF), L180
(800MHz)
?
Check filter between
U1 and U2 (VHF/UHF).
U202, U205 (800MHz)
NO
RF
Signal
YES
at L6 (VHF/ Check U1 Stage.
U202 (800MHz)
UHF), L201
(800MHz)
?
800MHz
NO OR
Check U201 filter.
WEAK RF
RF
Program filter to
Signal at
schematic test freqs.
YES VHF
CR109 (VHF/
and check varactor
UHF), CR102
voltages.
UHF
(800MHz)
?
NO
Check harmonic filter L126-127,
ant. switch, CR109, J2 contact
(VHF/UHF). CR102, L105, L103,
L106, C101, C114 (800MHz)
Bad SINAD
Bad 20Db Quieting
No Recovered Audio
Spray or Inject 1st IF into
XTAL Filter
IF FREQS:
FL1.
45.15 VHF
73.35 UHF/800MHz
NO
Audio
Heard?
Check 2nd LO
Cntrl Voltage
at R413
YES NO
VCO
Locked?
Check Q601
bias Circuitry
for Faults.
YES
Q601
Collector Check
NO
OK?
for
IF signal
3.0VDC
present?
NO
YES
Check R601,
R602
Is
circuit
NO
from Q601 to Replace bad
U401 components.
good?
YES
Before replacing U401,
check U401 voltages.
Check for no Rx audio
VOCON flowchart C.29.
Before replacing U401 check 2nd
VCO Q1. Check VCO O/P level;
C408, C425. Disconnect R416 and
If voltages OK check verify that a 0.5V to 5V ctrl voltage
varactor filter. If voltages not VCO will sweep about the IF freq.
OK, check U102. Check
also Q108, R115, U102
voltages. Check U102 can
be selected by MCU
before replacing U102.
Check FGU,
2.1Mhz NO
Chart C.31 - VHF/
Check
UHF C.32 -
at Pin 19
800MHz
U401?
YES
Check U401voltages
14.4MHz
NO
and programming &
at ABACUS
14.4MHz VCO
(U401) pin
components.
15?
YES
Rotate Freq. Knob
Activity Check J1. If
NO
On U401 OK, Check "No Rx
Sel Pin? Audio" Chart C.29
YES
MAEPF-24386-O

Chart 28. VHF/UHF/800 MHz Receiver RF

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