November 16, 2006 6881094C31-E
5-28 Troubleshooting Charts: VOCON RX Audio
5.12 VOCON RX Audio—Page 1
MAEPF-27394-A
* on NTN9564, NNTN4563 & NNTN4819 VOCON boards
** on NNTN4717 VOCON board
Probe R406 for
Frame Sync Signal,
Compare with
RX SAP waveform,
Trace 1
Frame
Sync
Present?
Replace U301*
(FLIPPER)
Probe R403 for
Data, Compare
with RX SAP
waveform, Trace 2
Signal
Present?
THD <3%?
Clock
Present?
Probe R405
for Clock Signal,
Compare with
RX SAP
waveform, Trace 3
Go to
RX RF
flowchart
Data
Present?
Check
Distortion of
Signal at C533
Replace U501
(GCAP II)
Check Preamp
Input Signal at
C533
NoNo
No
No
No
Ye s
Ye s
Ye s
Ye s
1
Ye s
Bad SINAD
Bad 20db Quieting
No Recovered Audio
Inject Standard
Input into Antenna
Connector
A standard input is an
RF signal with a 1 kHz
tone modulated with 3 kHz
deviation in a 25 kHz channel.
Replace U401**
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