Tait TM8000 Series Service Manual page 180

Figure 9.5 Components of the interface circuitry on the top-side of the main board at the corner
Task 1 —
Check Output Lines
180 Diagnosis of Faults on Main Board
For an output line suspected or reported to be faulty, compare actual and
expected signals as described below. If necessary, determine what an
expected signal should be by copying the faulty radio's programming file
into a serviceable radio and measuring the relevant points on the latter.
1. Check the electrical signal at the appropriate pin of a connector
mated to the radio connector in question. If the expected
connector signal is not present, go to Step 3. If it is, go to Step 2.
2. If the expected signal is present, there might be no fault on that
line or there could be an intermittent fault. Subject the radio to
mild mechanical shock or vibration, or to a temperature change.
This might expose any intermittent contact, in which case go to
Step 3.
3. If the expected signal is not present, check whether the expected
internal signal is present. If it is, go to Step 5. If it is not, go to
Step 4.
4. The fault lies with the radio's internal circuitry. If the power-
supply circuitry or the CODEC and audio circuitry is suspect,
continue with the fault diagnosis as in
Subsection 9.7
to Subsection 8.1
5. The fault lies in the filtering, basic processing, or connector for the
line under test. Re-solder components or replace damaged or
faulty components as necessary. Confirm the removal of the fault
and return to Subsection
return to Subsection 8.1
assembly.
respectively. If the digital board is suspect, return
and replace the complete main-board assembly.
8.1. If the fault could not be found,
and replace the complete main-board
TM8100 Mobile Radio Service Manual
Subsection 9.1 and
May 2004 © Tait Electronics Limited