Motorola Astro Digital Mobile Radio Xtl5000 Detailled 6881096c74 B Manual

							6881096C74-BMay 25, 2005
Troubleshooting Procedures: VHF (136–174 MHz) Band Main Board Troubleshooting 4-7
4.6.3 Out-of-Lock Condition
The probable cause of an out-of-lock condition is a failure in the synthesizer circuit. If the voltages on 
the AUX 1*, AUX 2*, AUX3*, and AUX4* lines do not conform to required output frequency in
Table 4-5, troubleshoot the synthesizer.
If the AUX 1* to AUX 4* voltages are correct but the synthesizer feedback level is not within the 
range indicated, troubleshoot the feedback path.
If the AUX 1* to AUX 4* voltages are correct and the synthesizer feedback level is correct but an 
out-of-lock condition persists, troubleshoot the synthesizer.
4.6.4 FGU Troubleshooting Aids
The following illustrations are additional service aids for troubleshooting the frequency generation 
unit.
•Figure 4-1 on page 4-8 is a block diagram of the DC distribution for the frequency generation 
unit.
•Figure 4-2 on page 4-9 is a block diagram of the frequency generation unit.
•Table 4-6 on page 4-9 describes the function of pins on the LV Frac-N IC U3751.
•Figure 4-3 on page 4-11 is a waveform representation during programming of the LV Frac-N IC 
U3751.Table 4-5.  AUX Output Frequency Requirements
Frequency 
RangeAUX 1AUX 2AUX 3AUX 4Output Frequency
HI LOW LOW LOW 136–155 MHz
LOW HI LOW LOW 155–174 MHz
LOW LOW HI LOW 245.65–264.65 MHz
LOW LOW LOW HIGH 264.65–283.65 MHz 
						

							May 25, 20056881096C74-B
4-8Troubleshooting Procedures: VHF (136–174 MHz) Band Main Board Troubleshooting
Figure 4-1.  Frequency Generator Unit DC Power Supply Distribution (VHF)
MAEPF-27803-O_VHF
13.8 VDC
from Battery or
Power Supply
Q0503
Switched A+
Switched A+
(SW_A+)
9.3V
Regulated
5.0V
Regulated8.2V
RegulatedK9.1
3.0V
Regulated U0950
9.3V Regulator
U0505
5.0V Regulator
U3750
3.0V Regulator
Y3750 16.8
MHz Reference
Oscillator and
U3752 BufferQ3756
8.2V Superfilter
Q3753,Q3754
TX VCOs
and
Q3751,Q3752
RX VCOs
U3751
LVFracNQ3762 3rd
Stage of RX
Injection
Q3761 1st
Stage of RX
InjectionU0951
9.1V TX
Regulator
Q3760 and
Q3759 TX
InjectionQ0952
K9.1 Switch
Q3758 3rd
Ste of TX
Injection
Charge Pump
Bias Q3755 and
Q3750, Prescaler
Amp Q3757
Q3758 3rd
Stage of TX
Injection
Q3769 2nd
Stage of RX
Injection 
						

							6881096C74-BMay 25, 2005
Troubleshooting Procedures: VHF (136–174 MHz) Band Main Board Troubleshooting 4-9
Figure 4-2.  Frequency Generation Unit Block Diagram (VHF)
Table 4-6.  LV Frac-N U3751 Pin Descriptions (VHF)
Pin No.Pin NameDescription
1AUX2 Auxiliary logic output, high selects Low TX VCO
2AUX3 Auxiliary logic output, high selects Low RX VCO
3AUX4 Auxiliary logic output, high selects High RX VCO
4LOCK Lock detect—logic high indicates in-lock condition
5PD_VDD 3.0-V supply (phase detector)
6GROUND Ground (digital)
7DATA SPI data I/O
8CLK SPI clock
9CEX SPI enable line—active low
10MODIN Modulation input from controller
11VMULT4 Multiplier clock output
12VMULT3 Multiplier clock output

  		
	
	

	
	








 
  


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							May 25, 20056881096C74-B
4-10Troubleshooting Procedures: VHF (136–174 MHz) Band Main Board Troubleshooting
13
VRO 3.0-V supply for reference oscillator warp circuitry
14VMULT2 Not used
15VMULT1 Not used
16INDMULT Not used
17— No connection
18REFSEL Not used
19FREFOUT Not used
20AVDD 3.0-V supply (analog)
21VBPASS Not used
22GND Ground (analog)
23XTAL1 16.8 MHz reference oscillator input
24XTAL2 Not used
25WARP Reference oscillator warp output
26SFCAP Superfilter bypass node
27SFBASE Superfilter control node for Q6759
28SFOUT Superfilter output
29— No connection
30SFIN Superfilter supply input
31— No connection
32PREIN Prescalar input
33GROUND Ground (prescalar)
34PRE_VDD 3.0-V supply
35PVREF Not used
36DVDD 3.0-V supply (digital)
37TEST1 Not used
38TEST2 Not used
39CPB2 Phase detector bias input
40CPB1 Phase detector bias input
41MODOUT Modulation output
42CCOMP Not used
43IOUT Phase detector normal mode output
44GND Ground (phase detector)
45IADAPT Phase detector adapt mode output
46ADAPTSW Phase detector adapt switch
47VCP High-voltage supply for phase detector
48AUX1 Auxiliary logic output, high selects Low TX VCO Table 4-6.  LV Frac-N U3751 Pin Descriptions (VHF) (Continued)
Pin No.Pin NameDescription 
						

							6881096C74-BMay 25, 2005
Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting 4-11
Figure 4-3.  Waveform Representation During Programming of the LV Frac-N IC (U3751)
NOTE:The above waveforms are representations only.
4.6.5 No or Low Output Power (TX or RX Injection)
In addition to the schematic and theory of operation, refer to the transmitter injection troubleshooting 
flowchart and the receiver injection trouble shooting flowchart in Chapter 5. The charts will guide you 
through a sequence of tests and checks designed to isolate problems in the Transmitter or receiver 
injection strings.
4.6.6 No or Low Modulation
In addition to the schematic and theory of operation, refer to the transmitter no TX Audio 
troubleshooting flowchart in Chapter 5. The chart will guide you through a sequence of tests and 
checks designed to isolate problems in the Transmitter Audio section of the FGU.
4.6.7 Troubleshooting the Back-End
Refer to “5.6.4 RX Back-End—Poor SINAD or No Audio (136–174 MHz)—Part 1 of 3” on page 5-18.
4.7 UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting
This information will help you troubleshoot the RF section of the UHF Range 1 (380–470 MHz) band 
XTL 5000 radio. Use this information, along with the theory of operation and troubleshooting charts, 
to diagnose and isolate the cause of failures.
Prior to troubleshooting, it is important to review the theory of operation, including specific 
precautions and troubleshooting methods. Because much of the radios circuitry operates at high 
frequencies, measurements must be taken very carefully. Notes and cautions are added to the text 
to alert you to this need in areas of greatest sensitivity. However, the need for extreme care does 
exist in all measurements and tests.
4.7.1 Display Flashes “FAIL 001”
This display indicates a synthesizer “out-of-lock” condition. The following information will help to 
trouble shoot the frequency generation unit to the component level. Perform the following checks to 
determine the mode of the Fail 001:
1. Determine if the “out-of-lock” condition occurs in either receive mode, transmit mode, or both. 
Also, check other frequencies programmed in the unit if available.
2. To determine if the “out-of-lock” is frequency or VCO dependant, place the unit into RF TEST 
Mode, as described in the ASTRO Digital XTL 5000 VHF/UHF Range 1/UHF Range 2/700–
800 MHz Mobile Radio Basic Service Manual (6881096C73) and step through each test 
channel. Table 4-7 on page 4-12 indicates the frequency and Aux logic level for each test 
mode channel. In addition, Table 4-8 on page 4-12 provides information about the frequency 
of operation for each VCO.
Pin 9 (Chip Select)
Pin 7 (Data)
Pin 8 (Clock)
MAEPF-27805-O 
						

							May 25, 20056881096C74-B
4-12Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting
NOTE:The UHF band radios use high-side injection with an IF frequency of 109.65 MHz; therefore, 
the receive VCO frequencies are 109.65 MHz higher than the selected radio channel 
frequencies.
NOTE:If a failure is indicated in any of the VCOs, whose operation is defined in the table above, then 
the respective circuit should be checked to ensure proper bias is being applied to the 
transistor. Specifically, the transistor collector pin should be at 8.2 V and base-emitter voltage 
should be on the order of 0.8 V. The steering line voltage should be in the range of 2 V for the 
lower frequency end of operation, and on the order of 11V at the upper frequency end of 
operation. There could be typically +/- 1 V deviation from the above quoted numbers, which 
allow for tolerances in the components. A clean, steady, frequency spike should be observed 
on a spectrum analyzer of typically -18 dBm at the end of the resistive pad in the collector 
circuitry of a properly working VCO.
3. Continue troubleshooting by using the Fail 001 troubleshooting chart in Chapter 5. Table 4-7.  Test Mode Channels UHF Range 1 (AUX 4 is not used for VCO selection in UHF)
Test 
ModeAUX (TX Logic)TX 
VCOTX Freq 
(MHz)
AUX (RX Logic)RX 
VCORX Freq 
(MHz)
RX VCO 
Freq 
(MHz)123123
Chan 1000Q5825380.0250010Q5901380.0750489.7250
Chan 2
000Q5825391.4750010Q5901391.4250501.0750
Chan 3
000Q5825408.9750010Q5901408.9250518.5750
Chan 4
000Q5825424.9375110Q5903424.9875534.6375
Chan 5
100Q5826425.0250110Q5903425.0750534.7250
Chan 6
100Q5826436.0250110Q5903436.0750545.7250
Chan 7
100Q5826455.8750001Q5905455.8250565.4750
Chan 8
100Q5826469.9375001Q5905469.9875579.5750
Table 4-8.  VCO Frequency Calculation and Switching Logic (UHF Range 1)
VCOAUX1AUX2AUX3VCO Frequency
RX VCO Q5901010489.65 
						

							6881096C74-BMay 25, 2005
Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting 4-13
4.7.2 FGU Troubleshooting Aids
The following illustrations are additional service aids for troubleshooting the frequency generation 
unit.
•Figure 4-4 is a block diagram of the DC distribution for the frequency generation unit.
•Figure 4-5 on page 4-14 is a block diagram of the frequency generation unit.
•Table 4-9 on page 4-14 describes the function of pins on the LV Frac-N IC U5752.
•Figure 4-6 on page 4-16 is a waveform representation during programming of the LV Frac-N IC 
U5752.
Figure 4-4.  Frequency Generation Unit DC Power Supply Distribution (UHF Range 1)
13.8 VDC
from Battery or
Power Supply
Audio
PAQ5503 RFPA 
Final
MRF1570
Q5502 RFPA 
Driver
MRF1518
U5501 RFPA 
Pre-driver
C65
Q0503
Switched A+
Switched A+
(SW_A+)
9.3V
Regulated9.1V
Regulated9.3V
Regulated
5.0V
Regulated5.0V
Regulated
8.2V
RegulatedK9.1
3.0V
Regulated U0950
9.3V Regulator
U0505
5.0V RegulatorU5301
5.0V 
Regulator
U5750
3.0V Regulator
Y5750 16.8
MHz Reference
Oscillator and
U6752 BufferQ5752
8.2V Superfilter
Q5825, Q5826 TX VCOs
and
Q5901, Q5903, Q5905 
RX VCOs
U5752
LVFracNU5303 2nd
Stage of RX
Injection
Q5902, Q5904, Q5906
Stages of RX
InjectionU0951
9.1V TX
Regulator
Q5828 and
Q5829 TX
InjectionQ0952
K9.1 Switch
Q5501 
TX
Buffer
Charge Pump
Bias Q5750 and
Q5751 , Prescaler
Amp Q5755
U5570
9.3V Regulator A+ 
						

							May 25, 20056881096C74-B
4-14Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting
Figure 4-5.  Frequency Generation Unit Block Diagram (UHF Range 1)
Table 4-9.  LV Frac-N U6751 Pin Descriptions (UHF Range 1)
Pin No.Pin NameDescription
1AUX2 Auxiliary logic output
2AUX3 Auxiliary logic output
3AUX4 Auxiliary logic output
4LOCK Lock detect—logic high indicates in-lock condition
5PD_VDD 3.0-V supply (phase detector)
6GROUND Ground (digital)
7DATA SPI data I/O
8CLK SPI clock
9CEX SPI enable line—active low
10MODIN Modulation input from controller
11VMULT4 Multiplier clock output
12VMULT3 Multiplier clock output
13VRO 3.0-V supply for reference oscillator warp circuitry
14VMULT2 Not used
Bias 1 3.0V3.0V
3.0V
3.0V
8.2VLock Detect
to ControllerPrescaler Input
Q5755RF
Feedback 8.2V Bias 2
9.3VSFIN
SFBASE
SFOUTLock PREINAUX4AUX3
Mod OutIADAPTIOUT AUX2AUX1 VMULT4 VMULT3 5.0V16.8MHz Reference
to Controller and
Receiver Back End
VOLTAGE
MULTIPLIER
D5750 and
D5751 16.8MHz OSC
8.2V
Super Filter
Q5752U5751
U5752 3.0V
Regulator
U5750 
PHASE
DETECTOR BIAS
Q5750 RX and
Q5751  TXCLOCK
SYN_SEL
D ATA
MOD_IN From
Controller
NCAX0
X1
X2
X3
X4 B
C
7.5V 8.2V
Q5706
Q5707
Q5708
Q5709RX
INJECTIONTX
INJECTION
RX
InjectionTX
Injection Keyed
9.1V
C5779
C5780LOOP
FILTER8.2V SW
8.2V SW8.2V SW
8.2V SW
Q5825
Q5826
Q5901
Q5903
Q5905
U5753
Q57108.2V SW 
						

							6881096C74-BMay 25, 2005
Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting 4-15
15
VMULT1 Not used
16INDMULT Not used
17— No connection
18REFSEL Not used
19FREFOUT Not used
20AVDD 3.0-V supply (analog)
21VBPASS Not used
22GND Ground (analog)
23XTAL1 16.8 MHz reference oscillator input
24XTAL2 Not used
25WARP Reference oscillator warp output
26SFCAP Superfilter bypass node
27SFBASE Superfilter control node for Q5752
28SFOUT Superfilter output
29— No connection
30SFIN Superfilter supply input
31— No connection
32PREIN Prescalar input
33GROUND Ground (prescalar)
34PRE_VDD 3.0-V supply
35PVREF Not used
36DVDD 3.0-V supply (digital)
37TEST1 Not used
38TEST2 Not used
39CPB2 Phase detector bias input
40CPB1 Phase detector bias input
41MODOUT Modulation output
42CCOMP Not used
43IOUT Phase detector normal mode output
44GND Ground (phase detector)
45IADAPT Phase detector adapt mode output
46ADAPTSW Phase detector adapt switch
47VCP High-voltage supply for phase detector
48AUX1 Auxiliary logic output Table 4-9.  LV Frac-N U6751 Pin Descriptions (UHF Range 1) (Continued)
Pin No.Pin NameDescription 
						

							May 25, 20056881096C74-B
4-16Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting
Figure 4-6.  Waveform Representation During Programming of the LV Frac-N IC (U5752)
NOTE:The above waveforms are representations only.
4.7.3 Out-of-Lock Condition
The probable cause of an out-of-lock condition is a failure in the synthesizer circuit. If the voltages on 
the AUX lines do not conform to Table 4-8 on page 4-12, troubleshoot the synthesizer. If the AUX 
pins are correct, but the supply switch (Q5706, Q5707, Q5708, Q5709 or Q5710) to the in question 
VCO is not active with 8.2V at the VCO end, then troubleshoot the 3 to 8 multiplexer U5753 or the 
switch transistor packages. 
If the AUX voltages are correct but the synthesizer feedback level is not within the range indicated at 
TP5783 (-6 to -11dBm), troubleshoot the buffer stages after the VCO. If the AUX voltages are correct 
and the synthesizer feedback level is correct but an out-of-lock condition persists, troubleshoot the 
synthesizer.
4.7.4 No or Low Output Power (TX or RX Injection)
In addition to the schematic and theory of operation, refer to the transmitter injection troubleshooting 
flowchart and the receiver injection trouble shooting flowchart in Chapter 5. The charts will guide you 
through a sequence of tests and checks designed to isolate problems in the Transmitter or receiver 
injection strings.
4.7.5 No or Low Modulation
In addition to the schematic and theory of operation, refer to the transmitter no TX Audio 
troubleshooting flowchart in Chapter 5. The chart will guide you through a sequence of tests and 
checks designed to isolate problems in the Transmitter Audio section of the FGU.
4.7.6 Troubleshooting the Back-End
Refer to “5.6.18 RX Back-End—Poor SINAD or No Audio (380–470 MHz and 450–520 MHz)—Part 1 
of 3” on page 5-32.
Pin 9 (Chip Select)
Pin 7 (Data)
Pin 8 (Clock)