Motorola ASTRO Digital Saber Service Manual page 100

No Receive Audio
(Vocoder Failure)
Set radio to test mode
CSQ. Inject a 1KHz
modulated signal at the
carrier frequency at
-60dBm level with
3KHz deviation.
Verify standard bias
per table Table 3.
Isolate and
No
Standard
repair problems.
bias OK?
See chart C.5.
Yes
Verify signals
present at ADSIC
(U406) per Fig. W10
and Fig. W5. Note
DOUT and DOUT* are
low level voltage
signals.
During a mode
change, verify an
ABACUS
programming
sequence occurs
per Fig. W4
Yes
No Signals
probing on the
present?
ABACUS carrier.
ABACUS is No Verify SBI signal
programmed connection
? between ADSIC and
ABACUS ICs.
Repair as
necessary. If
Yes
connection good,
Fault lies with replace U406.
transceiver board.
Refer to appropriate
section. Chart C.30
Synopsis
This failure indicates a lack of
received audio with the fault
lying with the vocoder. It
assumes a functional
transceiver board and no power
up fail codes were displayed.
Since all received signal modes
occur through this same path,
this failure applies to digital/
PL,DPL, etc. Failure modes are
as follows:
1) Missing DSP IRQB interrupt.
2) Lack of 2.4 REF clock and/or
data from ABACUS.
3) Missing clock or data on SSI
port from ADSIC.
4) Non functional control of or
faulty Audio PA.
5) Damaged speaker or speaker
flex.
6) Faultu ADSIC.
Verify signals per
Fig. W7 at points
indicated.
Replace
Yes Speaker/Flex
Signals
assembly after
present?
verifying continuity
of signal paths.
No
1
No
Replace U406.
Verify signals per Fig.
No
W2 at points
indicated.
No
Signals
Replace U406.
present?
At this point the fault
Yes
could lie with a faulty
ADSIC, or it could be
the DSP does not Check for continuity
see/service the IRQB between U405 and
or SC1 interrupt from U406 of the signals
ADSIC! depicted in Fig. W2
and the 8KHz IRQB.
Repair
connections.
Connections
Replace U406.
good?
No
Yes
Yes
Alert tone
audible?
Perform radio
function which
causes an alert
tone to be
No
generated.
Replace U405.
10-18
1
Fig. W7-
Trace 1
present?
Yes
Fig. W7-
Trace 2
present?
Yes
Replace
Fig. W7-
Speaker/Flex
Trace 3 or 4 No
assembly after
not present or
verifying continuity
in phase?
of signal paths.
Yes
Make sure no
Verify signals
external
EXT/INT_SPKR
mic/speaker is
and AMPEN at
attached to
U401 are logic
universal
high.
connector which
would cause the
radios to select
EXT_SPKR.
Control
Yes
Replace U401.
signals
correct?
No
Replace U406 if continuity
of signals EXT/INT_SPKR
and AMPEN from U401 to
U406 verifies..
MAEPF-24406-A
Chart 29 . No RX Audio