Tait TB7100, Service Manual

Page: 270 / 370

272 Transmitter Fault Finding (25W) TB7100 Service Manual
© Tait Electronics Limited October 2005
Task 33 —
Check Components
of LPF
If there are no faults in the final RF signal path up to and including the PIN
switch, then 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. See
Figure 13.19 . Check for shorts,
open circuits, and faulty components. Repair any fault.
4. Enter the CCTM command
326 5
to set the transmitter power level
to the maximum.
5. Enter the CCTM command
101 x x 0
, where
x
is the lowest
frequency (in hertz) for maximum power, as given in Table 13.8
(B1 band) or Table 13.9 (H5, H6).
6. Enter the CCTM command 33 to place the radio in transmit mode.
7. Measure the RF output power. This should exceed 35W.
8. Enter the CCTM command
32
to place the radio in receive mode.
9. Enter the CCTM command 101 x x 0 , where x is the highest
frequency (in hertz) for maximum power, as given in Table 13.8
(B1 band) or Table 13.9 (H5, H6).
10. Repeat Steps Step 6 to Step 8 .
11. If the power in both the above cases exceeds 35 W, the fault has been
rectified; go to
“Final Tasks” on page 123 . If it does not, the repair
failed; replace the main-board assembly and go to “Final Tasks” on
page 123 .
RF output power: more than 35W