No Or Low Output Power (Tx Or Rx Injection); No Or Low Modulation; Troubleshooting The Back-End; Standard Bias Tables - Motorola ASTRO Digital XTL 5000 Detailed Service Manual

4-28

Figure 4-12. Waveform Representation During Programming of the LV Frac-N IC (U6751)

NOTE: The above waveforms are representations only.
4.9.3

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.
4.9.4

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.
4.9.5

Troubleshooting the Back-End

Refer to "5.6.36 RX Back-End—Poor SINAD or No Audio (700–800 MHz)—Part 1 of 3" on page 5-
50.

4.10 Standard Bias Tables

Table 4-16, below, outlines some standard supply voltages and system clocks that should be present
during normal operation. These should be checked as a first step to any troubleshooting procedure.
Nominal Value
13.8 V
13.8 V
13.8 V
13.8 V
2.83 V
2.5 V
9.1 V
9.1 V
May 25, 2005
Pin 9 (Chip Select)
Pin 7 (Data)
Pin 8 (Clock)

Table 4-16. Standard Operating Bias: Power Lines

Signal Name
A+ (at DC connector)
IGNITION
SW_A+
(on board only)
SW_B+ (from C.H.)
SW_B+_SENSE
SW_B+_ON_OFF
(on board only)
9.3V_ABACUS
9.3V
Troubleshooting Procedures: Standard Bias Tables
MAEPF-27805-O
Range/State
11.0 to 16.6 V
11.0 to 16.6 V
11.0 to 16.6 V
11.0 to 16.6 V
No change
2 to 3 V
No change
No change
Probe Locations
J0401-20, TP0414
J0401-19, J0401-21
U0500-4, Q0503
TP0413, J0401-17
U0604-7
Q0505-1, Q0504-1
U0505-1
TP0951, TP0950
6881096C74-B