Motorola ASTRO Digital Spectra, Instruction Manual

Page: 77 / 114

6881086C22-B 55
TRC Local TX Troubleshooting Chart
Check/replace
U110 and U105
No
Is 1kHz
signal present
at J1-23?
Check/replace
U101.
Yes
No
Is 1kHz
signal present
at J6-1?
Check control head and
mic operation as specified
in ASTRO Spectra Detailed
Service Manual.
Inject a 90mVrms
1kHz signal into
the mic input of
the control head.
Set up
radio for test.
No
Is 1kHz
signal present
at C605?
Yes
Mic Hi
VU Meter
(Tape Out)
Check VB, 9.6V and
FILTER_CLOCK signal,
also, be certain HY2
is inserted properly.
No
Is 1kHz
signal present
at U114-13?
Check for
proper operation
of U124.
Yes
No
No
Is 1kHz
signal present
at U114-14?
Check/replace
U106.
No
Is 1kHz
signal present
at J3-46?
Yes
Determine why
U123 is holding
signal low and
repair.
No
Is 1kHz
at line1
output?
Yes
Check 9.6V and VB,
also, evaluate
operation of U111 and
position of R545 wiper.
Check HY2 for
correct operation and
replace if necessary.
Is
WL_MUTE
signal high?
Check/replace
U113 and U114.
No
Is 1kHz
signal present
at TP3?
Yes
Yes
Yes
Yes
Yes
Yes
Refer to TRC
Board Voltage
Troubleshooting
Chart.
No
Is
9.6V and VB
present?
Check for
correct operation
of U127 and U123.
No
Is
FILTER_CLOCK
signal a 0-5V square
wave at
110.4kHz?
4
4
1
2
3
4
1
2
3
4
Check/replace
U105.
No
Is 1kHz
signal present
between R556
and R559?
Yes
4
5
6
6
6
3
3
4
5
6
Check/replace
transformer.
No
Is
signal at
secondary of
T100?
Yes
Check 9.6V and VB;
also, check for
correct operation
of U111.
Check/replace
Q114 and/or
Q115.
No
Is
signal at
U111-1?
Yes
TRC LOCAL TX
STOP
MAEPF-26156-A