Radio Shack TRC-447, Service Manual

Page: 10 / 52

— 10 —
Unit will not tum on
Check the voltage
of IC502.
Power ON
NG
Check the power
SW VR601.
NG
Replace IC502.
OK
OK
OK
Is display normal?
Check the voltage
at IC502.
Replace IC502.
NG
Replace Fuse.
NG
OK
Check the
oscillation at pin
26 of IC401.
Check the
voltage at pin 25
of IC401.
Check the voltages
of IC403.
Replace IC403.
NG
OK
Check the
voltages of IC402
and Q401.
OK
Replace IC402
and/or Q401.
NG
Replace X401.
the voltages
of Q407, Q404
and Q405.
OK
Replace Q407
and/or Q404, Q405.
NG
Check
Check the
soldering of the cable
between MAIN and FRONT
PCBs.
Replace soldering.
NG
NG
NG
NG
NG
OK
OK
OK
Check the
voltage of D703.
Replace D703.
NG
Check the Fuse.
OK
Check RX and TX
sections.
OK
OK
TROUBLESHOOTING
SYSTEM CONTROL SECTION CLOCK