Tait TM8000 Series Service Manual page 235

Task 16 —
Power and Current
Are Low
Table 9.11 RF output power of individual RF power amplifiers at different frequencies
Frequency band
B1
D1
H5
H6
TM8100 Mobile Radio Service Manual
May 2004 © Tait Electronics Limited
7. If not already done, remove the
circuit between the test capacitor and the common drain of Q309
[at 3F3/3E5] and Q310 [at 3F2/3D5] (see
Figure 9.19 as well as
for faulty, shorted or misplaced components in this part of the
circuit. Repair any fault.
8. Repeat Steps 1 to 4 of Task 14. Remove the test lead and test
capacitor, and resolder the coupling capacitors in position. If the
power and current are now correct at all three frequencies, the
fault has been rectified; return to
go to Task 10.
If the RF output power and the supply current are uniformly low at all
frequencies, one of the PAs is suspect or the input to the PAs is reduced.
Check each PA in turn:
For the first PA (Q310), enter the CCTM command 331 to check
1.
the DAC value of final bias 1 (
a returned.
2. Note the current reading on the DC power supply. Enter the
CCTM command 331 1 to turn off final bias 1.
Enter the CCTM command 33 to place the radio in transmit
3.
mode. Note the RF output power measured at the test set. This
should be as shown in Table 9.10. If it is, go to Step 4 to repeat
the check with the second PA. If it is not, carry out Task 5 and
then Task 6.
For the second PA (Q309), enter the CCTM command 332 to
4.
check the DAC value of final bias 2 (
value b returned.
5. Note the current reading on the DC power supply. Enter the
CCTM command 332 1 to turn off final bias 2.
6. With the radio still in transmit mode, note the RF output power
measured at the test set. This should be as shown in Table 9.10.
If it is, go to Task 10. If it is not, carry out Task 5 and then Task 7.
Lowest frequency
29 ± 5 W
33 ± 5 W
5 ± 5 W
13 ± 5 W
PAF TOP
Figure 9.27 and Figure
Subsection
CDC TX FIN BIAS
CDC TX FIN BIAS
Frequency within band
Centre frequency
34 ± 5 W
28 ± 5 W
12 ± 5 W
19 ± 5 W
Diagnosis of Faults on Main Board
can. Check for an open
Figure 9.18 and
9.28). Also check
8.1. If they are not,
1). Record the value
2). Record the
Highest frequency
29 ± 5 W
29 ± 5 W
27 ± 5 W
28 ± 5 W
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