Motorola Astro Digital Mobile Radio Xtl5000 Detailled 6881096c74 B Manual

							6881096C74-BMay 25, 2005
Troubleshooting Procedures: UHF Range 2 (450–520 MHz) Band Main Board Troubleshooting 4-17
4.8 UHF Range 2 (450–520 MHz) Band Main Board Troubleshooting
This information will help you troubleshoot the RF section of the UHF Range 2 (450–520 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.
4.8.1 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 4-10 indicates the frequency and Aux logic level for each test mode channel. 
In addition, Table 4-11 on page 4-18 provides information about the frequency of operation for 
each VCO.
Table 4-10.  Test Mode Channels UHF Range 2 (AUX 4 is not used for VCO selection in UHF)
Te s t  
ModeAUX (TX Logic)TX 
VCOTX Freq 
(MHz)
AUX (RX Logic)RX 
VCORX Freq 
(MHz)
RX VCO 
Freq 
(MHz)123123
Chan 1100Q5826450.025001Q5905450.075559.725
Chan 2
100Q5826455.825001Q5905455.625565.275
Chan 3
100Q5826463.675001Q5905463.625573.275
Chan 4
100Q5826473.375110Q5903473.325582.975
Chan 5
100Q5826484.975110Q5903484.925594.575
Chan 6
000Q5825485.025110Q5903485.075594.725
Chan 7
000Q5825490.825110Q5903490.875600.525
Chan 8
000Q5825496.625010Q5901496.675606.325
Chan 9
000Q5825508.375010Q5901508.325617.975
Chan 10
000Q5825519.975010Q5901519.925629.575 
						

							May 25, 20056881096C74-B
4-18Troubleshooting Procedures: UHF Range 2 (450–520 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 4-11.  VCO Frequency Calculation and Switching Logic (UHF Range 2)
VCOAUX1AUX2AUX3VCO Frequency
RX VCO Q5905001559.65 
						

							6881096C74-BMay 25, 2005
Troubleshooting Procedures: UHF Range 2 (450–520 MHz) Band Main Board Troubleshooting 4-19
4.8.2 FGU Troubleshooting Aids
The following illustrations are additional service aids for troubleshooting the frequency generation 
unit.
•Figure 4-7 is a block diagram of the DC distribution for the frequency generation unit.
•Figure 4-8 on page 4-20 is a block diagram of the frequency generation unit.
•Table 4-12 on page 4-20 describes the function of pins on the LV Frac-N IC U5752.
•Figure 4-9 on page 4-22 is a waveform representation during programming of the LV Frac-N IC 
U5752.
Figure 4-7.  Frequency Generation Unit DC Power Supply Distribution (UHF Range 2)
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
4-20Troubleshooting Procedures: UHF Range 2 (450–520 MHz) Band Main Board Troubleshooting
Figure 4-8.  Frequency Generation Unit Block Diagram (UHF Range 2)
Table 4-12.  LV Frac-N U6751 Pin Descriptions (UHF Range 2)
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 2 (450–520 MHz) Band Main Board Troubleshooting 4-21
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 4-12.  LV Frac-N U6751 Pin Descriptions (UHF Range 2) (Continued)
Pin No.Pin NameDescription 
						

							May 25, 20056881096C74-B
4-22Troubleshooting Procedures: 700–800 MHz Main Board Troubleshooting
Figure 4-9.  Waveform Representation During Programming of the LV Frac-N IC (U5752)
NOTE:The above waveforms are representations only.
4.8.3 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 4-11 on page 4-18, 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.
4.8.4 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.
4.8.5 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.
4.8.6 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.
4.9 700–800 MHz Main Board Troubleshooting
This information will help you troubleshoot the RF section of the 700–800 MHz 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.
Pin 9 (Chip Select)
Pin 7 (Data)
Pin 8 (Clock) 
						

							6881096C74-BMay 25, 2005
Troubleshooting Procedures: 700–800 MHz Main Board Troubleshooting 4-23
4.9.1 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/UF Range 2/700–
800 MHz Mobile Radio Basic Service Manual (6881096C73) and step through each test 
channel. Table 4-13 indicates the frequency and Aux logic level for each test mode channel. 
In addition, Table 4-14 provides information about the frequency of operation for each VCO.
Table 4-13.  Test Mode Channels (700–800 MHz)
Te s t  
MODELV F r a c - N
TX LogicTX 
OscillatorTX Freq 
MHzLV F r a c - N  
RX LogicRX 
OscillatorRX Freq 
MHz
CHAN 1 AUX 1 U6754 osc1 762.0125 AUX 3 U6755 osc1 762.0625
CHAN 2 AUX 1 U6754 osc1 769.0125 AUX 3 U6755 osc1 769.0625
CHAN 3 AUX 1 U6754 osc1 775.9875 AUX 3 U6755 osc1 775.9375
CHAN 4 AUX 1 U6754 osc1 794.0125 AUX 4 U6755 osc2 851.0625
CHAN 5 AUX 1 U6754 osc1 805.9875 AUX 4 U6755 osc2 860.0625
CHAN 6 AUX 2 U6754 osc2 806.0125 AUX 4 U6755 osc2 860.0625
CHAN 7 AUX 2 U6754 osc2 823.9875 AUX 4 U6755 osc2 869.9375
CHAN 8 AUX 2 U6754 osc2 851.0125 AUX 4 U6755 osc2 851.0625
CHAN 9 AUX 2 U6754 osc2 860.0125 AUX 4 U6755 osc2 860.0625
CHAN 10 AUX 2 U6754 osc2 869.8875 AUX 4 U6755 osc2 869.9375
Table 4-14.  VCO Frequency Calculation and Switching Logic (700–800 MHz)
MODE
Radio 
Frequency 
(MHz)VCO 
Frequency 
FormulaVCO 
Frequency 
(MHz)AUX
1AUX
2AUX
3AUX
4
Rx 764.0125 - 
775.9875F(U6755 osc1) = 
Fc + 73.35 MHz837.3625 - 
849.3375Low Low HIgh Low
Rx 851.0125 - 
868.9875F(U6755 osc2) = 
Fc - 73.35 MHz777.6625 - 
795.6375Low Low Low HIgh
Tx (TA) 764.0125 - 
775.9875F(U6754 osc1) = 
Fc764.0125 - 
775.9875HIgh Low Low Low
Tx(RPTR) 794.0125 - 
805.9875F(U6754 osc1) = 
Fc794.0125 - 
805.9875HIgh Low Low Low
Tx(RPTR) 806.0125 - 
823.9875F(U6754 osc2) = 
Fc806.0125 - 
823.9875Low HIgh Low Low 
						

							May 25, 20056881096C74-B
4-24Troubleshooting Procedures: 700–800 MHz Main Board Troubleshooting
3. Continue troubleshooting by using the Fail 001 troubleshooting chart in Chapter 5.
4.9.2 FGU Troubleshooting Aids
The following illustrations are additional service aids for troubleshooting the frequency generation 
unit.
•Figure 4-10 on page 4-25 is a block diagram of the DC distribution for the frequency generation 
unit.
•Figure 4-11 on page 4-26 is a block diagram of the frequency generation unit.
•Table 4-15 on page 4-26 describes the function of pins on the LV Frac-N IC U6751.
•Figure 4-12 on page 4-28 is a waveform representation during programming of the LV Frac-N 
IC U6751.
Tx (TA) 851.0125 - 
868.9875F(U6754 osc2) = 
Fc851.0125 - 
868.9875Low HIgh Low Low
Tx (TA) = Talkaround Mode
Tx(RPTR) = Repeater or trunked
Table 4-14.  VCO Frequency Calculation and Switching Logic (700–800 MHz) (Continued)
MODE
Radio 
Frequency 
(MHz)VCO 
Frequency 
FormulaVCO 
Frequency 
(MHz)AUX
1AUX
2AUX
3AUX
4 
						

							6881096C74-BMay 25, 2005
Troubleshooting Procedures: 700–800 MHz Main Board Troubleshooting 4-25
Figure 4-10.  Frequency Generation Unit DC Power Supply Distribution (700–800 MHz)
MAEPF-27803-O
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
U6750
3.0V Regulator
Y6750 16.8
MHz Reference
Oscillator and
U6752 BufferQ6759
8.2V Superfilter
U6754 TX VCOs
and
U6755 RX VCOs
U6751
LVFracNQ6763 2nd
Stage of RX
Injection
Q6762 1st
Stage of RX
InjectionU0951
9.1V TX
Regulator
Q6764 and
Q6765 TX
InjectionQ0952
K9.1 Switch
Q6766 3rd
Ste of TX
Injection
Charge Pump
Bias Q6757 and
Q6758, Prescaler
Amp Q6761 
						

							May 25, 20056881096C74-B
4-26Troubleshooting Procedures: 700–800 MHz Main Board Troubleshooting
Figure 4-11.  Frequency Generation Unit Block Diagram (700–800 MHz)
Table 4-15.  LV Frac-N U6751 Pin Descriptions (700–800 MHz)
Pin No.Pin NameDescription
1AUX2 Auxiliary logic output, high selects U6754 OSC2
2AUX3 Auxiliary logic output, high selects U6755 OSC1
3AUX4 Auxiliary logic output, high selects U6755 OSC2
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
Bias 1 3.0V3.0V
3.0V
3.0V
8.2V8.2V 8.2V
Q6753
Q6755
Q6756
Q6760
Lock Detect
to ControllerPrescaler Input
Q6761RF
FeedbackRX
INJECTIONTX
INJECTION
RX
InjectionTX
Injection Keyed
9.1V
U6754
U6755
8.2V C6783LOOP
FILTER
Bias 2
9.3V9.3V
SFIN
SFBASE
SFOUTLock PREINAUX4AUX3 Mod OutIADAPTIOUT AUX2AUX1 VMULT4 VMULT3 5.0V16.8MHz Reference
to Controller and
Receiver Back End
VOLTAGE
MULTIPLIER
D6751 and
D6752 16.8MHz OSC
8.2V
Super Filter
Q67598.2V SW
8.2V SW8.2V SW
8.2V SW U6752
U6751 3.0V
Regulator
U6750
PHASE
DETECTOR BIAS
Q6757 RX and
Q6758 TXCLOCK
SYN_SEL
D ATA
MOD_IN From
Controller
MAEPF-27804-O