Tait TB7100, Service Manual, Page: 142 / 370

144 Frequency Synthesizer Fault Finding TB7100 Service Manual
© Tait Electronics Limited October 2005
11.1 Initial Checks
Types of checks
There are two different types of initial checks, which are covered in the
following tasks:
■
Task 1 : calibration checks
■
Task 2 : lock status
Which, if any, of these tasks needs to be carried out depends on the
symptoms of the fault.
Symptoms of Fault
The symptoms of the fault may be divided into three categories:
■
radio fails to power up and
System error
is displayed
■
Out of lock is displayed
■
radio is in lock but exhibits transmit or receive fault
In the first two cases the checks of Task 1 and Task 2 respectively are
required. In the last case there are several symptoms; these are listed below.
Transmit and
Receive Faults
A transmit or receive fault will be implied by one of the following
consequences:
■
radio fails to receive or receive performance is degraded
■
radio fails to enter transmit mode
■
radio exits transmit mode unexpectedly
■
radio enters transmit mode but fails to transmit
■
radio enters transmit mode but transmit performance is degraded
With a fault of this kind, neither of the initial tasks is required.
Fault diagnosis should begin with
“Power Supplies” on page 147 .
Summary
To summarize, given the nature of the fault, proceed to the task or section
indicated below:
■
Task 1 : system error
■
Task 2 : lock error
■
“Power Supplies” : transmit or receive fault
The checks of Task 1 and Task 2 will indicate the section with which the
fault diagnosis should continue. Note that there are some differences in the
fault-diagnosis procedures, depending on whether the radio is a UHF (H5
and H6 bands) or VHF (B1 band) radio. The product-code label on the
radio body will identify the frequency band as described in
“Introduction”
on page 11 .