TM8100 Mobile Radio Service Manual Diagnosis of Faults on Main Board 233
May 2004 © Tait Electronics Limited
Task 12 —
Check PIN Switch
If there is no fault in the directional coupler, check the PIN switch as
follows:
1. Remove the
PIN TOP can.
2. Remove the three blocking capacitors C361, C362 and C363 [at
3N3/3E11] (see Figure 9.29).
3. Solder one terminal of a 33 pF (D1 band) or 22 pF (B1, H5, H6)
test capacitor to the PCB at the point shown in Figure 9.29.
Mount the capacitor vertically. Use a test capacitor of the type
GRM111, DLI C17, Murata 1210, or the equivalent.
4. Solder a 50 Ω test lead to the PCB. Solder the outer sheath to the
test pad shown in Figure 9.29, and solder the central wire to the
other terminal of the test capacitor.
5. Connect the test lead to the test set and measure the RF output
power. This should exceed 35 W. If it does, remove the test lead
and test capacitor, resolder the blocking capacitors in position, and
go to Task 13. If it does not, go to Step 6.
6. The PIN switch is not drawing the expected current. Check
D307 [at 3M3/3E10] (see Figure 9.29). If it is not faulty, go to
Step 7. If D307 is faulty, replace it, 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. Check the +9
V0_TX supply to the PIN switch via R3000 [at
3M5/3J10], and R389 and R390 [at 3M5/3F10] on the bottom-
side of the PCB (see Figure 9.23 and Figure 9.24). Replace any
faulty component and again measure the RF output power. If it
is correct, the fault has been rectified; if it is not, the repair failed.
Remove the test lead and test capacitor, resolder the blocking
capacitors in position, and return to Subsection 8.1. If the repair
had failed, replace the complete main-board assembly.
Task 13 —
Check Components
of LPF
If there is no fault in the directional coupler or PIN switch, the fault
should lie in the LPF. Check the LPF as follows:
1. Remove the
LPF TOP can.
2. Connect the RF connector to the test set.
3. Check the capacitors and inductors of the LPF between the PIN
switch and the RF connector. Check for shorts, open circuits, and
faulty components.
4. Repair any fault and measure the RF output power. This should
exceed 35 W. If it does, the fault has been rectified; return to
Subsection 8.1. If it does not, the repair failed; return to
Subsection 8.1 and replace the complete main-board assembly.
To Next Page
Loading...
Need help?
General
