Tait TM8000 Series, Service Manual

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TM8100 Mobile Radio Service Manual Diagnosis of Faults on Main Board 171
May 2004 © Tait Electronics Limited
9 Diagnosis of Faults on Main Board
Introduction
The previous section describes how to determine which module of
circuitry on the main board is faulty. This section provides guidelines for
locating and rectifying faults within a suspect module. The section is
divided into seven subsections which cover the seven modules
concerned:
■
power-supply circuitry
■
interface circuitry
■
frequency synthesizer
■
frequency control loop
■
receiver
■
transmitter
■
CODEC and audio circuitry
For obtaining replacements for faulty components, refer to
Subsection 8.2 (on page 166) . For a discussion of SMT repair
techniques, refer to Subsection 4.4 (on page 91) ; refer to this subsection
also regarding the replacement of the capacitors C548 and C565 and the
inductors L601 and L602.
Grid References
Throughout this section data in square brackets are grid references giving
the locations of the components concerned on the circuit diagram. The
first reference in square brackets is for the B1, H5 and H6 bands, and the
second is for the D1 band. Using the first reference in the next
subsection as an example, the format is thus: [at 6F7/6E6].
9.1 Power-supply Circuitry
Two Types of Fault
Fault diagnosis of the power-supply circuitry is divided into four tasks.
Which tasks are applicable depends on the nature of the power-up fault.
There are two cases: Firstly, either the radio fails to power up
immediately when power is applied, or it fails to power up when power
is applied and the
ON
/
OFF
key is pressed. Secondly, the radio powers up
when the
ON
/
OFF
key is pressed, but not for a power-up option for which
it is configured. With the first type of fault, carry out Tasks 1 to 3. With
the second type of fault, carry out Task 4.