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...

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)...

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...

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...

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...

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...

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...