Tait TP9100 Service Manual

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TP9100 Service Manual CODEC and Audio Fault Finding 279© Tait Electronics Limited May 2005Task 7 óCheck Signalfrom CODECFirst generate an appropriate audio test signal and check whether the signalis present at the output of the CODEC circuitry.1. Enter the CCTM command 400 x, where x is a valid channel number.(A suitable channel will depend on the programming of the radio.)2. Enter the CCTM command 21 to force unmuting of the receivedaudio signal.3. Enter the CCTM command 110 128 to set the audio level at itsmidpoint.4. At the test set apply 60%, 1kHz modulation to the RF signal.Reduce the volume to a minimum.5. Enter the CCTM command 324 r5.6. Check the received signal is present at pin 4 of connector PL1(see Figure 12.1). The signal should be:7. If the signal is correct, the fault is with PL1 or the accessory flexconnector. Refer to “Accessories Interface Faulty” on page 147 foraccessory connector service instructions. If the signal is not correct goto Step 8.8. Check the received signal is present at the junction of E900 and C909(see Figure 12.1). The signal should be:9. If the signal is correct go to Step 10. If it is not, go to Task 8.10. Check the soldering and components around PL1, E900, and C909(see Figure 12.1). Repair any fault.11. Confirm the removal of the fault and go to Step 12. If the repair failedor the fault could not be found, replace the main board and go to“Final Tasks” on page 134.12. If there is also a fault with the transmit modulation, notwithstandingmodulation at the accessory connector, go to Task 15. If there is noother fault, go to “Final Tasks” on page 134pin 4 of PL1: received signal with 1.2V DC offsetjunction of E900 and C909: received signal with 1.2V DC offset