Tait TB7100, Service Manual

Page: 189 / 370

TB7100 Service Manual Frequency Synthesizer Fault Finding 191
© Tait Electronics Limited October 2005
Task 34 —
Power Supply
If the FCL is suspect, first check that the 3 V power supply is not the cause
of the fault.
1. If not already done, remove the main-board assembly from the chassis
and place the radio in CCTM.
2. Measure the supply +3
V
0
AN
at the via shown in Figure 11.15 .
The via is adjacent to the
CDC TOP
can.
3. If the voltage is correct, go to “VCXO and TCXO Outputs” on
page 192 . If it is not, the 3 V regulator IC603 is suspect; go to Task 3
of “Power Supply Fault Finding” on page 132 .
via adjacent to CDC TOP can: 3.0
±
0.3 V DC
Figure 11.15 TCXO circuitry under the CDC TOP can
IF TOP CAN
VIA FOR MEASURING 3 V DC SUPPLY