Motorola ASTRO XTL 1500 Detailed Service Manual page 166

Troubleshooting Charts: Troubleshooting Tables
Table 5-2. XTL 1500 Troubleshooting Table (700–800 MHz, 380-470 MHz and 136-174 MHz) (Continued)
Symptom
No RX Audio/ ABACUS Circuit
Receive Does not (380-470 MHz,
Unsquelch (cont.) 450-520 MHz)
ABACUS Circuit
(700-800 MHz)
Radio Will Not Turn On/Off Switch
Off (Control Head)
Emergency Circuit
SW_B+ Sense
Circuit
6815854H01-A
Check Section Troubleshooting Procedure
• Check for 20 kHz Frame Sync
pulse signal at testpoint FS
(U5002-31)
• Check for 1.2 MHz Clock
square wave at testpoint
CLKOUT (U5002-28)
• Check for random data pattern
at testpoint DOUTA (U5002-29)
• Check for Clock Oscillator at
R5025 (18 MHz)
• Check for Local Oscillator at
C5058 (71.1 MHz or 75.6 MHz)
• Check for 20 kHz Frame Sync
pulse signal at testpoint FS
(U6000-31)
• Check for 1.2 MHz Clock
square wave at testpoint
CLKOUT (U6000-28)
• Check for random data pattern
at testpoint DOUTA (U6000-29)
• Check for Clock Oscillator at
R6003 (18 MHz)
• Check for Local Oscillator at
C6026 (71.1 MHz or 75.6 MHz)
Check for SW_B+_CH at 0 V at
J0401-17, TP0413
Check for 0 V at Timer U0506-3,
U0508-2,4
Check that U0604-7 is low (0 V)
and that SOFT TURN OFF is low
(0 V) at D0501
Component
• Absence of signal causes no
receive. Possible U5002
(ABACUS) failure or U0001
(Microprocessor Board) failure
• Absence of signal causes no
receive. Possible U5002
(ABACUS) failure or U0001
(Microprocessor Board) failure
• Absence of signal causes no
receive. Possible U5002
(ABACUS) failure or U0001
(Microprocessor Board) failure
• Absence of Clock signal
causes no receive. Possible
U5002 (ABACUS), Clock VCO,
or U0001 (Microprocessor
Board) failure
• Absence of LO signal causes
no receive. Possible U5002
(ABACUS), or LO VCO
• Absence of signal causes no
receive. Possible U6000
(ABACUS) failure or U0001
(Microprocessor Board) failure
• Absence of signal causes no
receive. Possible U6000
(ABACUS) failure or U0001
(Microprocessor Board) failure
• Absence of signal causes no
receive. Possible U6000
(ABACUS) failure or U0001
(Microprocessor Board) failure
• Absence of Clock signal
causes no receive. Possible
U6000 (ABACUS), Clock VCO,
or U0001 (Microprocessor
Board) failure
• Absence of LO signal causes
no receive. Possible U6000
(ABACUS), or LO VCO
A high voltage may indicate
failure with the control head
A high voltage may indicate
failure with U0506, or that the
EMERGENCY line is not
grounded by the rear accessory
cable
Absence of this voltage may
indicate failure with U0604 (Op-
Amp) or with U0001
(Microprocessor Board)
June 15, 2005
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