Motorola Astro Digital Mobile Radio Xtl5000 Detailled 6881096c74 B Manual

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-41
5.6.27 RF Power Amplifier (RFPA)—No or Low TX Power Output (380–470 MHz and 
450–520 MHz)—Part 2 of 5
Figure 5-31.  RF Power Amplifier (RFPA)—No or Low TX Power Output (380–470 MHz and 450–520 MHz)—
Part 2 of 5
Defective parts
 in matching network
between Q5502 and
Q5503?
(Note 9)Repair/replace
defective parts Yes
No
Defective parts
 in matching network
between U5501 and
Q5502?
(Note 5)
Repair/replace
defective parts Yes
Q5502 bias voltages
 as per Table 1?
(Note 6)
No
Is Q5502,
 gate resistance <
 1 MOhms?
(Note 7)YesRepair/replace
Q5502 and retune
gate bias via
Tuner
 (see help text)
NoNo
Yes
Is Q5502,
 drain resistance <
 1 MOhms?
(Note 8)Yes
No
Q5503 bias
voltages as per Table 1?
(Note 10)
Defective parts
in matching network
between Q5503 and
antenna switch?
(Note 13)
Antenna switch
 bias voltages as per
Table 1?
(Note 14)
Repair/replace
defective parts
Is Q5503,
 gate resistance <
 1 MOhms?
(Note 11)Yes
No
Is Q5503,
 drain resistance <
 1 MOhms?
(Note 12)Yes
No
Repair/replace
defective parts NoNo
Yes
YesYes
No
Repair/replace
Q5502 and retune
gate bias via
Tuner
 (see help text)
Check/repair/replace 
defective parts or 
GOTO Power Control 
- No/low VGBIAS 
Chart
Repair/replace 
Q5503 
(see General Notes) 
and retune gate bias 
via Tuner 
(see help text)  
 
B
A
Repair/replace 
Q5503 
(see General Notes) 
and retune gate bias 
via Tuner 
(see help text) Check/repair/replace 
defective parts or 
GOTO Power Control 
- No/low VGBIAS 
Chart 
						

							May 25, 20056881096C74-B
5-42Troubleshooting Charts: Flowcharts
5.6.28 RF Power Amplifier (RFPA)—No or Low TX Power Output (380–470 MHz and 
450–520 MHz)—Part 3 of 5
Figure 5-32.  RF Power Amplifier (RFPA)—No or Low TX Power Output (380–470 MHz and 450–520 MHz)—
Part 3 of 5
YesDefective parts in
antenna switch?
(Note 15)Repair/replace
defective parts
Defective parts in
 harmonic filter?
(Note 16)
No
Yes
Repair/replace
defective parts
No
Defective parts in
 power detector?
(Note 17)Yes
Repair/replace
antenna connectorContinuity check
 fails from R5713 and
the antenna connector
external coax?
No
Yes
Repair/replace
defective parts
B
Go to the
Controller GPIO
Section
No 
						

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-43
5.6.29 RF Power Amplifier (RFPA)—No or Low TX Power Output (380–470 MHz and 
450–520 MHz)—Part 4 of 5
Specific Notes:
1. Remove C5508 and solder the center conductor of a small 50-ohm, coaxial cable to TP5502. 
Solder ground to the gold shield track adjacent to TP5502. Attach an RF milliwatt meter, key 
the transmitter, and measure TX_INJ power. Then, remove the coaxial cable and replace 
C5508. Remove the solder added to shield track.
2. Remove R0977 in the power control section, and measure the resistance between VCNTRL 
(TP5503) and ground. Replace R0977.
3. If U5501, VD1, is incorrect, inspect the bias feed circuitry (L5502 and C5505) and interstage 
match components (L5503, C5509, and C5507). If U5501, RFOUT, is incorrect, inspect the 
bias feed circuitry (L5505 and C5517).
4. Remove L5502 and measure the resistance between VD1 (U5501 pin 14) and ground. 
Replace L5502. Remove L5505 and measure the resistance between RFOUT (U5501 pin 6) 
and ground. Replace L5505.
5. Inspect C5566, C5516, C5518, and R5511-15.
6. If the Q5502 gate bias is incorrect, inspect the bias feed circuitry (R5516, L5525, C5556, and 
R5527). If the bias feed circuitry is functional, then go to the Power Control—No or low 
VGBIAS flowchart. If the Q5502 drain bias is incorrect, inspect the bias feed circuitry (L5508, 
C5526-27, R5517, E5501, and R5574). Check U5570, Q5770, and associated circutry.
7. Remove R5516 and measure the resistance between Q5502 gate and ground. Replace 
R5516.
8. Remove L5508 and measure the resistance between Q5502 drain and ground. Replace 
L5508.
9. Inspect C5559-60, C5535, C5538, R5530, R5533-34, and R5536.
10. If the Q5503 pin 7 gate bias is incorrect, inspect the bias feed circuitry (R5520, C5539, 
C5557, and R5525). If the gate bias feed circuitry is functional, then go to the Power 
Control—No or low VGBIAS flowchart. If the Q5503 pin 6 gate bias is incorrect, inspect the 
bias feed circuitry (R5521, C5540, C5558, and R5526). If the bias feed circuitry is functional, 
then go to the Power Control—No or low VGBIAS flowchart. If the Q5503 pins 2 and 3 
common drain bias is incorrect, inspect the bias feed circuitry (L5510, C5549-50, R5522-23, 
and E5502).
11. Remove R5520 and measure the resistance between Q5503 pin 7 gate and ground. Replace 
R5520. Remove R5521 and measure the resistance between Q5503 pin 6 gate and ground.  
Replace R5521.
12. Remove L5510 and measure the resistance between Q5503 pins 2 and 3 drain and ground. 
Replace L5510.
13. Inspect R5535, C5542-43, C5545-48, and C5551-53.
14. If the antenna switch bias voltages are incorrect, inspect R5524, L5701-4, and R5701, as well 
as perform diode checks on D5701-3.
15. Inspect the remaining antenna switch parts (C5701-10).
16. Inspect L5706-8, L5712-13, C5708, C5711-14, C5719-20, R5713, and R5718.
17. Inspect D5704, R5707-8, R5702-4, and C5715-16. 
						

							May 25, 20056881096C74-B
5-44Troubleshooting Charts: Flowcharts
5.6.30 RF Power Amplifier (RFPA)—No or Low TX Power Output (380–470 MHz and 
450–520 MHz)—Part 5 of 5
Table 5-6.  RFPA DC Voltages
DescriptionLocationVoltage (Vdc) 
(380–470 MHz)Voltage (Vdc) 
(450–520 MHz)
A+ = 13.6 Vdc
U5501, VD1 U5501 pin 14 9.0–9.3 9.0–9.3
U5501, RFOUT U5501 pins 6 and 7 9.0–9.3 9.0–9.3
Q5502 Gate Bias R5516/C5525 
node1.8–2.0 1.8–2.1
Q5502 Drain Bias L5508/R5517
Node9.0–9.3 9.0–9.3
Q5503 Gate Bias 1 R5520/C5539 
node2.0–2.2 1.4–1.9
Q5503 Gate Bias 2 R5521/C5540 
node2.0–2.2 1.4–1.9
Q5503 Drain Bias L5510/R5523
Node13.0–13.6 13.0–13.6
Antenna Switch Bias
Voltage 1L5701/C5702 
node~4.7 ~5.95
Antenna Switch Bias
Voltage 2D5701/D5702 
node~4.0 ~5.0
Antenna Switch Bias
Voltage 3D5703/R5701 
node~3.3 ~3.3 
						

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-45
5.6.31 RFPA Power Control—No VGBIAS (380–470 MHz and 450–520 MHz)
Figure 5-33.  RFPA Power Control—No VGBIAS (380–470 MHz and 450–520 MHz)
Read General
Notes before
proceeding. Read
specific notes as
indicated
START
NoYes
Repair/replace
U0960
No
No/low 
Q5503 pin 7 
VGBIAS1?
No/low 
Q5503 pin 6 
VGBIAS2?
Remove U0960.
TP0937 voltage
 2.6-2.8 V? Yes
Remove U0960.
TP0939 voltage
 2.6-2.8 V? Yes
Remove U0960.
TP0941 voltage
 2.0-2.2 V? No
Repair/replace
U0959.  If problem
still not fixed, see
IC communication
in CONTROLLER
section.
Yes
Yes
No
No 
						

							May 25, 20056881096C74-B
5-46Troubleshooting Charts: Flowcharts
5.6.32 No 16.8 MHz Reference Oscillator Frequency (700–800 MHz)
Figure 5-34.  No 16.8 MHz Reference Oscillator Frequency (700–800 MHz)
MAEPF-27813-O
U6752DC Voltages
Pin 1
Pin 2
Pin 3
Pin 4
Pin 5No connection
1.5
Ground
1.5
3
>800mVpp
16.8MHz? Probe pin 3
of Y6750 for
16.8MHzSTART
No 16.8MHz
Reference
No
Ye s
>800mVpp
at TP6764?No
Ye sCheck
C6817Replace
Y6750 3.0VDC
at pin 1 of
Y6750?No
Ye sCheck 3.0V
regulator path
from U6750
>500mVpp
at pin 2
U6752?No
Ye sCheck C6758
and R6756
>3.0Vpp
at pin 4
U6752?No
Ye sCheck
U6752
>1.4Vpp
at TP6762?NoCheck L6756,
C6755, C6759,
R6756 and C6760Measure 16.8MHz Signals
with Oscilloscope having a
bandwidth >100MHz.
NOTE:  L6756 and C6755 filter the
distorted output of U6752 resulting
in a clean sinusoidal 16.8MHz signal.
R6757 and C6759 adjust the amplitude.
Check Controller
Section and/or
ABACUS IC
U6000Ye s 
						

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-47
5.6.33 Poor RX Sensitivity or No RX Audio (700–800 MHz)—Part 1 of 2
Figure 5-35.  Poor RX Sensitivity or No RX Audio (700–800 MHz)—Part 1 of 2
MAEPF-27875-O
Poor Rx
Sensitivity or no
Rx audio
Measure Transceiver
Sinad by injection
signal at antenna portYe s
Ye s3kHz FM Deviation
1kHz Audio  tone
Sinad
< - 119.1dBm?
Check RF level at
Mixer LO injection port
(U6251 Pin 3 side 1)Receiver
is working
properly
NoYe s
Good?
1Check Q6350,
Q6251, Q6252,
Q6253, Q6254
and make any
necessary repairs No
Ye s RF level
at ~ 14dBm?
Check RX front-end
filter switching
voltage TableCheck Receiver
VCO troubleshooting
flowchart
(LO injection section) No
Ye s
RX Switching Voltages
Receiving at
700MHz BandReceiving at
800MHz Band Test Points
TP6256, 58,
60, 62 TP6255, 57,
59, 61 TP6254
LNA U62500V
7.6V
2V3V
4V
7.6V
5V at Pin 1 
						

							May 25, 20056881096C74-B
5-48Troubleshooting Charts: Flowcharts
5.6.34 Poor RX Sensitivity or No RX Audio (700–800 MHz)—Part 2 of 2
Figure 5-36.  Poor RX Sensitivity or No RX Audio (700–800 MHz)—Part 2 of 2
MAEPF-27874-O
1
Inject a standard FM test
signal into the antenna port.
Use a spectrum analyzer and
high-impedance RF probe to
measure the signal at TP6253.

						

							6881096C74-BMay 25, 2005
Troubleshooting Charts: Flowcharts5-49
5.6.35 RX IF—Poor SINAD or No Audio (700–800 MHz)
Figure 5-37.  RX IF—Poor SINAD or No Audio (700–800 MHz)
MAEPF-27809-O
Level
is +4dB
referenced to the
RF input
level?No
No No Ye s
Measure the IF
signal level
(73.35MHz)
at TP6350 Measure the IF
signal level
(73.35MHz)
at TP6252
Refer to
troubleshooting
flow diagram for
Receiver Front End
Level
is +20dB
relative to the RF
input level?No
Ye s
Voltage
level of
>~5.0V at Q6350
Collector
(pin 3)? 
Ye s
Voltage
level of
0.7V at Q6350
Base
(pin 1)?
Ye s Refer to
troubleshooting
flow digram for
Receiver Back EndMeasure the DC
Bias voltage level
on transistor
Q6350
Replace
Q6350 Inspect biasing
components and
check Voltage
Regulator U0950 for
 normal operation
Inspect crystals and
matching networks for
missing components
and/or soldering defects 
						

							May 25, 20056881096C74-B
5-50Troubleshooting Charts: Flowcharts
5.6.36 RX Back-End—Poor SINAD or No Audio (700–800 MHz)—Part 1 of 3
Figure 5-38.  RX Back-End—Poor SINAD or No Audio (700–800 MHz)—Part 1 of 3
MAEPF-27806-O
Is the
IF level at
TP6350~+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 >~3.5V
at Q6000
Collector?
Voltage
level of ~2.15V
at Q6000 Base
(pin 1)? Measure Second LO
at C6026, top side
towards Abacus  III
(U6000) 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 75.6 or 71.1
MHz?Inspect biasing components
and solder. Replace Q6000
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?
Ye s
Go on to RX audio
troubleshooting
flowchartCheck Voltage Regulator
U0505 for normal operation,
look for base to emitter 
drop of ~1.2V on Q6001,
replace if necessary
START
Poor SINAD or
No Audio