230 Frequency Synthesizer Fault Finding TM8100/TM8200 Service Manual© Tait Electronics Limited June 20069.9 VCXO and TCXO OutputsTask 35 —VCXO Output If the 3V power supply is not faulty, check the VCXO output as follows:1. Use an oscilloscope probe to check the VCXO output at thefollowing position:2. If the signal is correct, go to Task 36. If it is not, go to Step 3.3. The VCXO circuitry under the VCXO BOT can is faulty. Remove theVCXO BOT can.4. Locate and repair the fault in the VCXO (Q501, Q503, XL501 andassociated components) (see Figure 9.18).5. Confirm the removal of the fault and go to Task 36. If the repairfailed, replace the board and go to “Final Tasks” on page 157.C536 — probe the via next to C536 (see Figure 9.17). The signalshould be:VCXO output at C536: sine wave of 1.1 ± 0.2 Vpp on 1.4 ± 0.2 V DCA4 band: IC509, pin 4 — probe the via next to R5044(see Figure 9.17). The signal should be:VCXO output at pin 4 of IC509: square wave of 1.5 ± 0.2 V pp
