Service manual

Troubleshooting Charts 5-3
68P81076C25-C July 1, 2002
Chart C.1 RF Board Back-End
Bad SINAD.
Bad 20Db Quieting.
No Recovered Audio.
Inject 1
st
IF
into Johnson connector
on RF board IF Freqs:
109.65MHz
Note: Inject Modulated On
Carrier Frequency
Signal As Required.
Change
Mode
Before Replacing
U301, Check 2nd
VCO.
"Second VCO Checks"
Check RX
Front End.
Check 2nd VCO
"Second VCO Checks"
Audio
Heard?
VCO
Locked?
2.1MHz
Check At
Pin 19
U301?
No
No
Yes
Yes
Yes
"Display Flashes
"FAIL 001""
No
14.4MHz
at ABACUS
U301 Pin
15?
Check U301 Voltages,
Programming, &
14.4MHz VCO
Components.
No
Yes
Activity
On U301
Sel Pin?
Check VOCON
Board.
No
Yes
MAEPF-25192-A