Tait TP9100 - Page 221

TP9100 Service Manual Transmitter Fault Finding 221
© Tait Electronics Limited May 2005
Tas k 1 —
7.5V Power Supply
First check the 7.5V power supply.
1. Remove
PA BOT can, PA LPF BOT can, and TX CONTROL BOT can, and carry
out a thorough visual inspection
2. Obtain a needle probe to use for measurements of the power supply
at the PA driver and PAs.
3. Set the DC power supply to 7.5V, with a current limit of 3A.
4. 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 10.2 on page 218.
5. Enter the CCTM command 326 4 to set the radio to high power.
Note Using the CCTM command 326 5 will set the radio to maximum
power and the driver stage will be under current limiting.
6. Attempt to place the radio in transmit mode. Enter the CCTM
command 33.
7. If the radio enters the transmit mode, continue with Step 8. If instead
a C03 error is displayed in response to the command 33, go to Tas k 5
on page 227.
8. Measure the voltage at the point on L115 shown in Figure 10.2.
This is the supply at the drain of Q106, and should be:
9. Also measure the voltage at the point on L111 shown in
Figure 10.2. This is the supply at the drain of Q103, and should be:
10. Enter the CCTM command 32 to place the radio in receive mode.
11. If the power supply measured in Step 8 and Step 9 is correct, go to
Task 2
. If it is not, go to “Power Supply Fault Finding” on page 149.
drain of Q106: approximately 7.0V DC
drain of Q103: approximately 7.0V DC