May 25, 2005 6881096C74-B
5-6 Troubleshooting Charts: Troubleshooting Tables
No RX Audio/
Receive Does not
Unsquelch (cont.)
ABACUS Circuit
(700-800 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)
• 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
Radio Will Not Turn
Off
On/Off Switch
(Control Head)
Check for SW_B+_CH at 0 V at
J0401-17, TP0413
A high voltage may indicate
failure with the control head
Radio Will Not Turn
Off (continued)
Emergency Circuit Check for 0 V at Timer U0506-3,
U0508-2,4
A high voltage may indicate
failure with U0506, or that the
EMERGENCY line is not
grounded by the rear accessory
cable
SW_B+ Sense
Circuit
Check that U0604-7 is low (0 V)
and that SOFT TURN OFF is low
(0 V) at D0501
Absence of this voltage may
indicate failure with U0604 (Op-
Amp) or with U0001
(Microprocessor Board)
Table 5-2. XTL 5000 Troubleshooting Table (700–800 MHz, 380-470 MHz and 136-174 MHz) (Continued)
Symptom Check Section Troubleshooting Procedure Component
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