Tait TB7100, Service Manual

Page: 149 / 370

TB7100 Service Manual Frequency Synthesizer Fault Finding 151
© Tait Electronics Limited October 2005
Task 4 —
6V Power Supply
If the output of the SMPS is correct, check the 6 V DC supply next.
1. Measure the supply +6
V
0 at pin 4 of IC606 (see Figure 11.2 ).
2. If the voltage is correct, go to Task 5 . If it is not, measure the 9 V
input at pin 5 of IC606 (see Figure 11.2 ).
3. If the voltage is correct, go to Step 4 . If it is not, the 9V regulator
IC601 is suspect; go to Task 3 of “Power Supply Fault Finding” on
page 132 .
4. If the input to the regulator IC606 is correct but not the output,
check IC606 (see
Figure 11.2 ) and the associated circuitry; if
necessary, replace IC606.
Remove the
SYN TOP
can and check the C-multipliers Q508 (pins 3,
4, 5) and Q512 for shorts (see Figure 11.2 ); replace any suspect
transistor.
5. If a fault is found, repair the circuit, confirm the removal of the fault,
and go to
“Final Tasks” on page 123 . If the repair failed or no fault
could be found, replace the main-board assembly and go to “Final
Tasks” on page 123 .
pin 4 of IC606: 6.0
±
0.3V DC
pin 5 of IC606: 9.0
±
0.3V DC