Tait TM8100 mobiles, Service Manual

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TM8100/TM8200 Service Manual Transmitter Fault Finding (>25W) 267
© Tait Electronics Limited November 2007
11 Transmitter Fault Finding (>25W)
Introduction
This section covers the diagnosis of faults in the 40W/50W and 30W/35W
transmitter circuitry. The main indication of a fault in the transmitter is a
reduction in range. This implies that the power output is wrong or too low.
Another type of fault is exhibited when the radio always transmits at full
power, even if set otherwise. Regardless of the fault, the lock status should
be normal.
Fault-Diagnosis
Tasks
The procedure for diagnosing transmitter faults is divided into tasks, which
are grouped into the following sections:
■
“Power Supplies”
■
“Transmitter RF Power”
■
“Biasing of PA Driver and PAs”
■
“RF Signal Path” .
Before beginning the fault diagnosis with “Power Supplies” , note the
following information regarding CCTM commands, frequency bands, can
removal and replacement, and transmit tests.
CCTM Commands
The CCTM commands required in this section are listed in Table 11.1 .
Full details of the commands are given in “Computer-Controlled Test
Mode (CCTM)” on page 123 .
>25W