Motorola Astro Digital Mobile Radio Xtl5000 Detailled 6881096c74 B Manual

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-31
5.6.17 RX IF—Poor SINAD or No Audio (380–470 MHz and 450–520 MHz)—Part 2 of 2
Figure 5-21.  RX IF—Poor SINAD or No Audio (380–470 MHz and 450–520 MHz)—Part 2 of 2
Level
is -3dB
referenced to 
C5403?No
No Ye s
Measure the IF
signal level
(109.65MHz)
at C5403 Measure the IF
signal level
at U5400-3
Check Y5401
No
Ye s
U5400-4 > 3V
and U5400-5 < 0.2V
(Without pre-amp)
U5400-4 < 0.2V
and U5400-5 > 3V
(With pre-amp)?  Same as level
at U5400-3 
(Without pre-amp)
or -10 dB referenced 
to level at U5400-3 
(With pre-amp)? 
Ye s Refer to
troubleshooting
flow digram for
Receiver Back EndMeasure the DC
 voltage level
at U5400-4
and U5400-5
Replace
U5400Troubleshoot 
Q5402 and 
associated 
circuitry 1 
						

							May 25, 20056881096C74-B
5-32Troubleshooting Charts: Flowcharts
5.6.18 RX Back-End—Poor SINAD or No Audio (380–470 MHz and 450–520 MHz)—
Part 1 of 3
Figure 5-22.  RX Back-End—Poor SINAD or No Audio (380–470 MHz and 450–520 MHz)—Part 1 of 3
Is the
IF level at
R5034 ~+20dB
relative to the
RF input?No
No
No
NoNo No
Ye s
Ye sYe s
Ye s Ye s
Signal
present?Voltage
level of >~4.3V
at Q5002
Collector?
Voltage
level of ~1.7V
at Q5002 Base
(pin 1)? Measure Second LO
at C5058, top side
towards Abacus  III
(U5002) pinRefer back to
Receiver IF
troubleshooting
flowchart
Measure Abacus
0-3V Digital SSI
lines FS,DOUTA,
and CLKOUT
3231
Are the
levels 0-3V?
No
Ye s
Ye s Frequency
CLKOUT at
1.2MHz?
No
3 No
FS = 20kHz
sync pulse? Frequency is 
107.4 or 111.9
MHz?Inspect biasing components
and solder. Replace Q5002
as necessary
Ye s
Visually inspect
the Second
LO VCO
Ye sNo Visual
examination
OK?Make repairs
as necessary
No problem
found
DOUTA=
24 bit I, 24
bit Q, 8 bit AGC word
(similar to fig X-X,
troubleshooting
waveforms)?
Ye s
Go on to RX audio
troubleshooting
flowchartCheck Voltage Regulator
U0505 for normal operation,
look for base to emitter 
drop of ~0.7V on Q5001,
replace if necessary 
						

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-33
5.6.19 RX Back-End—Poor SINAD or No Audio (380–470 MHz and 450–520 MHz)—
Part 2 of 3
Figure 5-23.  RX Back-End—Poor SINAD or No Audio (380–470 MHz and 450–520 MHz)—Part 2 of 3
No
33 1
R5013
= 5.0V?
No
Ye sYe s
R5013 = 0.0V? No
Ye s Freq 2nd LO 
VCO 
						

							May 25, 20056881096C74-B
5-34Troubleshooting Charts: Flowcharts
5.6.20 RX Back-End — Poor SINAD or No Audio (380–470 MHz and 450–520 MHz)—
Part 3 of 3
Figure 5-24.  RX Back-End—Poor SINAD or No Audio (380–470 MHz and 450–520 MHz)—Part 3 of 3
No
3
3
32
DC
voltage at
R5022 =
0.0V?
Ye s No
Ye s Freq of
CLKOUT

						

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-35
5.6.21 Low or No RX Injection Signal (380–470 MHz and 450–520 MHz)
Figure 5-25.  Low or No RX Injection Signal (380–470 MHz and 450–520 MHz)
Approx.
5V on
C5318?START
Low or No RX
Injection Signal
No
No
Ye sNo
Ye s Ye s
Approx.
4.5V on
pin 14
of U5303?5 V 
on C5335?
Check RF path
from RX VCOCheck R5324,
R5325, R5326 Check Voltage 
Regulator U5301
Check L5299 
						

							May 25, 20056881096C74-B
5-36Troubleshooting Charts: Flowcharts
5.6.22 Low or No TX Injection Signal (380–470 MHz and 450–520 MHz)
Figure 5-26.  Low or No TX Injection Signal (380–470 MHz and 450–520 MHz)
Approx.
3.4 V on
Q5828-C?START
Low or No TX
Injection Signal
No
Ye s
Check RF path
from TX VCOApprox.
6.5 V on
Q5501-C?No
Ye sCheck  Q5501 and
DC Bias Circuitry;
replace if
necessary Approx.
3.7 V on
Q5829-C?No
Ye sCheck  Q5829 and
DC Bias Circuitry;
replace if
necessary Check  Q5828 and
DC Bias Circuitry;
replace if
necessary 
						

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-37
5.6.23 No TX Audio (380–470 MHz and 450–520 MHz)
Figure 5-27.  No TX Audio (380–470 MHz and 450–520 MHz)
1.0Vpp
at R5755 or
TP5792?No
Ye s
0.4Vpp
at 
C5780?No
Ye sCheck deviation
tuning or replace
U5752 GOTO
Controller
Section
Check
synthesizer
loop filter
componentsNOTE:  After the modulated signal is coupled
through C5780 the signal is attenuated to levels
below 2mv making a measurement difficult for
most oscilloscopes. Inject a 2.0Vpp
1kHz tone into Mic
input and key radioSTART
No TX Audio
This Flow chart only checks the modulation
path of the FGU. Readings are typical and
can vary with deviation settings that are
programmed during tuning. 
						

							May 25, 20056881096C74-B
5-38Troubleshooting Charts: Flowcharts
5.6.24 TX or RX VCO Unlock (Fail 001) (380–470 MHz and 450–520MHz)—Part 1 of 2
Figure 5-28.  TX or RX VCO Unlock (Fail 001) (380–470 MHz and 450–520 MHz)—Part 1 of 2
Frequency
Detected? Sniff Frequency
near TX or RX
VCO or
infection stringTX or RX VCO
Unlock (Fail 001)
No
Ye s
Check VCO
Control Voltage
at TP57968.2VDC
at Collector of only
one of Q5706,
Q5707, Q5708, 
or Q5709 
Q5710?No
Ye s
3.0VDC
on pins 5, 36,
and 13 of
U5752?Check 9.3 Volt
supply path from
regulator U0950 in
Controller section
11.5VDC or
drifting?NoNo
Ye sCheck if VCO
is locked using
spectrum analyzer
13.5VDC
at Charge Pump
Capacitor
C5788?No
Ye sCheck Voltage
Multiplier
Circuitry
Go to
Controller
troubleshooting
charts Go to Transmitter
or receiver
Injection string
troubleshooting
chartsPlace an Inductive field probe
connected to a spectrum analyzer
near area to be sniffed.
Locked?
Ye s
3VDC
at pin 4 of
U5752?NoNo
Ye sCheck for short
on pin 4 to
controller or
replace U5752 Go to Transmitter
or receiver
Injection string
troubleshooting
charts
A 
						

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-39
5.6.25 TX or RX VCO Unlock (Fail 001) (380–470 MHz and 450–520 MHz)—Part 2 of 2
Figure 5-29.  TX or RX VCO Unlock (Fail 001) (380–470 MHz and 450–520 MHz)—Part 2 of 2
Check 3 Volt
supply path from
Regulator U5750
Check 3 Volt
supply pathCheck 3 Volt
supply path  Refer to Chart to determine
which AUX output determines
active VCO. 3VDC
at pin 5 of
U5750?NoCheck 5 Volt
supply path from
regulator U0505
Unlock
RX or
TX?TX
RX Ye s
Required 
Aux pins
 at 3.0VDC
for RX?No
No Ye sCheck
U5752
Check U5753, 
Q5708, Q5709, 
and Q5710Ye sRequired 
Aux pins
 at 3.0VDC
for TX?No
No Ye sCheck
U5752
Check
U5753, Q5706, 
and Q57073.0VDC at
E6750?
3.0VDC at
E6750?Ye s
A 
						

							May 25, 20056881096C74-B
5-40Troubleshooting Charts: Flowcharts
5.6.26 RF Power Amplifier (RFPA)—No or Low TX Power Output (380–470 MHz and 
450–520 MHz)—Part 1 of 5
NOTE:For each flowchart step in which reference is made to a note, be sure to refer to that specific 
note (located on page 61 of this flowchart) for guidance in performing the actual 
troubleshooting procedure. Also, RFPA DC voltages are shown in Table 5-6 on page 5-44.
Figure 5-30.  RF Power Amplifier (RFPA)—No or Low TX Power Output (380–470 MHz and 450–520 MHz)—
Part 1 of 5
Read General
Notes before
proceeding. Read
specific notes as
indicated
Check battery
cable, mic, and
control head
connections
START
Continuous red light
while mic button is
depressed?GOTO Sythesizer-
No Transmit
Chart
Tune power with
Tuner?
(see help text)
No
Yes
Tune current limit
with Tuner
(see help text) Yes
No
TX injection power
 less than 0.5 mW?
(Note 1)GOTO Sythesizer-
No or Low Tx
Injection
Chart  Yes
K9.1V
 present
 at Q0952, pin 1 in
power control section
when transmitter is
 keyed?
No
GOTO Power 
Control - No K9.1V 
Chart for 
700-800 MHz
RFPA_CNTRL
voltage (TP5503)
less than 4.8 V when 
 transmitter is
 keyed?
YesNo
GOTO Power 
Control - No or low 
RFPA_CNTRLChart 
for  700-800 MHz  No
U5501 drain biases
voltages per Table 1?
(Note 3)
Yes
No
Check/repair/
replace defective
parts
Yes
No
A
Is U5501,
 VCNTRL resistance <
 1 kOhms?
(Note 2)YesRepair/replace
U5501
No
Is U5501,
 RFOUT and VD1
resistance <
 1 MOhms?
(Note 4)Yes
Repair/replace
U5501