Tait TM8000 Series User Manual

228 Diagnosis of Faults on Main Board TM8100 Mobile Radio Service Manual
May 2004 © Tait Electronics Limited
Task 1 0 —
Trace Initial RF Signal
Path
If the biasing of the PA driver and the PAs is correct, investigate the initial
RF signal path in the transmitter circuitry.
1. Use an RF probe to measure the RF voltage after C300 [at
3A1/3C1] (see Figure 9.20 and Figure 9.21). This is the output
SYN TX LO from the frequency synthesizer. The required voltage
should be as given in Table 9.8 (B1 band), Table 9.9 (D1) or
Table 9.10 (H5, H6). If it is, go to Step 3. If it is not, go to Step 2.
2. Check C300. If C300 is not faulty, go to Subsection 9.3 on the
frequency synthesizer. If C300 is faulty, replace it and return to
Step 1.
3. If not already done, remove the
PAD TOP can. Measure the RF
voltage after C313 [at 3B0/3B2] (see Figure 9.20 and
Figure 9.21). This is the output of the buffer amplifier in the
exciter circuit. The required voltage should be as given Table 9.8
(B1 band), Table 9.9 (D1) or Table 9.10 (H5, H6). If it is, go to
Step 5. If it is not, go to Step 4.
4. Check the components around Q300 [at 3B0/3B2] (see
Figure 9.20 and Figure 9.21). Repair any fault. If these
components are not faulty, replace Q300. Confirm the removal
of the fault and return to Subsection 8.1. If the repair failed,
return to Subsection 8.1 and replace the complete main-board
assembly.
5. Measure the RF voltage after C301 [at 3A3/3E1] (see Figure 9.20
and Figure 9.21). This is the output of the exciter. The required
voltage should be as given in Table 9.8 (B1 band), Table 9.9 (D1)
or Table 9.10 (H5, H6). If it is, go to Step 7. If it is not, go to
Step 6.
6. Check the components between C313 and Q303 [at 3D0/3B3],
and between Q303 and R308 [3A3/3E1] (see Figure 9.20 and
Figure 9.21). Repair any f ault. If these components are not faulty,
replace Q303. Confirm the removal of the fault and return to
Subsection 8.1. If the repair failed, return to Subsection 8.1 and
replace the complete main-board assembly.
7. Measure the RF voltage at the drain of Q306 (B1 band) [at 3E3]
or after C317 and C389 (D1, H5, H6) [at 3D3/3E3] (see
Figure 9.20 and Figure 9.21). This is the output of the PA driver.
The required voltage should be as given in Table 9.8 (B1 band),
Table 9.9 (D1) or Table 9.10 (H5, H6). If it is, go to Step 9. If
it is not, go to Step 8.
8. Check the components between C301 [at 3A3/3E1] and Q306
(see Figure 9.20 and Figure 9.21). Repair any fault. If these
components are not faulty, replace Q306. Confirm the removal
of the fault and return to Subsection 8.1. If the repair failed,
return to Subsection 8.1 and replace the complete main-board
assembly.

Tait TM8000 Series Specifications

General

Brand	Tait
Model	TM8000 Series
Category	Radio
Language	English