Tait TM8100 mobiles Service Manual page 288

Task 10 —
Repair Output
Matching Circuitry
288 Transmitter Fault Finding (>25W)
If the checks in Task 9
there is a fault in the output matching circuitry.
1. If not already done, remove the
2. Check for faulty, shorted or misplaced components in the circuit
between the test capacitor and the common drain of Q309 and Q310
(see Figure 11.6). Repair any fault.
3. Program the radio with the highest frequency in the radio's frequency
band: Enter the CCTM command 101 x x 0, where x is the frequency
in hertz. The required values for the different frequency bands are
given in Table
Enter the CCTM command 33 to place the radio in transmit mode.
4.
5. Note the RF output power measured by the test set, and note the
current reading on the DC power supply.
RF output power: > 70W (VHF), > 60W (UHF), > 52W (700 MHz), > 58W (800 MHz)
current: < 15A (VHF), < 12A (UHF), < 12A (800 MHz)
Enter the CCTM command 32 to place the radio in receive mode.
6.
7. Program the radio with the centre frequency in the band: Enter the
CCTM command 101 x x 0, where x is the frequency in Hertz.
8. Repeat Step 4 to
9. Program the radio with the lowest frequency in the band: Enter the
CCTM command 101 x x 0, where x is the frequency in Hertz.
10. Repeat Step 4 to
11. Remove the test lead and test capacitor, and resolder the coupling
capacitors C348, C349 and C350 in position (see
12. If the power and current are now correct at all three frequencies, the
fault has been rectified; go to
not, go to Task 26
show that the power and current are still skewed,
PAF TOP
11.2.
Step 6.
Step 6.
"Final Tasks" on page
in "RF Signal Path" on page
© Tait Electronics Limited November 2007
can.
Figure 11.6).
163. If they are
316.
TM8100/TM8200 Service Manual