Tait TM8100 mobiles, Service Manual

Page: 257 / 620

TM8100/TM8200 Service Manual Receiver Fault Finding 257
© Tait Electronics Limited November 2007
K5 band only:
For the K band, check the circuitry as follows when the sensitivity loss is
moderate. For all other bands, the steps begin
on page 256 .
1. Remove the
FE TOP
can and, if not already done, the
IF TOP
can.
2. Check the soldering of all the components of the front-end circuitry
from
C400 to IC409 (see Figure 10.1 and Figure 10.4 ).
3. Check the 3V supply voltage at L420 and L421 ; use the measurement
points shown in Figure 10.1 .
4. Also check the LNA enable conditions. First measure V
c
on pin 1 of
the collector of IC404 or IC405 and ground (see Figure 10.1 ).
IC404 is enabled for channels between 850 to 970MHz, and IC405
is enabled for channels between 762 and 776MHz.
5. If the checks in Step 2 to Step 4 reveal no fault, go to Step 6 .
If there is a fault, repair it and go to Step 7 .
Table 10.2 Front-end tuning voltages and corresponding DAC values
Frequency band
Tuning voltages at five different frequencies
FE TUNE0 FE TUNE1 FE TUNE2 FE TUNE3 FE TUNE4
A4 band
Frequency (MHz)
DAC value
Voltage (V) 65.9
0 to 40
0 to 0.47 72.1
89 ± 15
1.05 ± 0.18 77.1
134 ± 15
1.58 ± 0.18 82.1
173 ± 15
2.04 ± 0.18 88.1
218 ± 15
2.56 ± 0.18
B1 band
Frequency (MHz)
DAC value
Voltage (V) 135.9
37 ± 20
0.44 ± 0.24 145.1
88 ± 15
1.04 ± 0.18 155.1
136 ± 15
1.60 ± 0.18 164.1
174 ± 15
2.04 ± 0.18 174.1
210 ± 15
2.57 ± 0.18
C0 band
Frequency (MHz)
DAC value
Voltage (V) 173.9
41 ± 20
0.48 ± 0.24 187.1
104 ± 15
1.22 ± 0.18 200.1
149 ± 15
1.75 ± 0.18 213.1
187 ± 15
2.20 ± 0.18 225.1
220 ± 15
2.59 ± 0.18
D1 band
Frequency (MHz)
DAC value
Voltage (V) 215.9
42 ± 20
0.5 ± 0.2 228.1
103 ± 15
1.2 ± 0.18 241.1
151 ± 15
1.7 ± 0.18 253.1
187 ± 15
2.2 ± 0.18 266.1
224 ± 10
2.6 ± 0.12
H5 band
Frequency (MHz)
DAC value
Voltage (V) 399.9
0 to 36
0 to 0.43 417.1
94 ± 15
1.11 ± 0.18 435.1
106 ± 15
1.25 ± 0.18 452.1
156 ± 15
1.84 ± 0.18 470.1
191 ± 15
2.25 ± 0.18
H6 band
Frequency (MHz)
DAC value
Voltage (V) 449.9
41 ± 20
0.48 ± 0.24 470.1
91 ± 15
1.07 ± 0.18 490.1
134 ± 15
1.58 ± 0.18 510.1
176 ± 15
2.07 ± 0.18 530.1
210 ± 15
2.47 ± 0.18
V
c
: 2.9±0.1V