Troubleshooting Flow Chart For Synthesizer - Motorola GTX 2000 Service Manual

Troubleshooting
Troubleshooting Charts
NO
Is U220 pin 32
AT = 13 VDC
Check C223-C230,
C240 and CR220
Is U220 pin 1
<0.7 VDC in RX &
>4.3 VDC in TX?*
Is U270 pin 1
NO
<0.7 V DC in
Check U400
RX and > 4.7 V
DC in TX?
NO
Is U220 pin 18
at 4.65 VDC?
If pin 18 is properly
soldered to the
PCB, replace U220.
Replace or
resolder
necessary
components
Troubleshooting Flow Chart
for Synthesizer
4-4
Correct
problem
YES
Fix
Connection
NO
YES Is connection
NO
between U220
pin 1 &
U270 pin 6 OK?
YES
Replace U220
YES
YES
Is RF level at
pin 20
between -10 &
+5 dBm?
YES
Are C241,C243,
NO
C245-C247, C249-
C253, L246,
R242,R244, and R245
OK?
GTX/GTX LTR/LTS 2000 Portable Radios Service Ma nual
Start
Visual
NO
check of the
board OK?
YES
+5V at U220
NO
pins
12,22,23
& 3
YES
NO
Are signals
at pins 9 &
10 of U220?
YES
NO
Is there a short
between pin 32 and
pins 9 & 10 of
U220?
YES
Remove
shorts
NO
If C271 and runners between
U220 pin 20 & U220 pin 15
are OK, then see VCO
troubleshooting chart.
YES
Replace U220
68P02945C75-A
Check 5V
Regulator
Is 16.8MHz
Check
NO
signal at
U210,
U220 pin 14?
R210,C232,R232.
YES
NO
Are waveforms
at pins 9 & 10
triangular?
YES
Do pins 5, 6 & 7
NO
of U220 toggle
when channel is
changed?
Check programming
lines between U709
YES
and U220 pins 5,6 & 7
NO
Is information
µ
from P U709
correct?
µ
Check P U709
troubleshooting
YES
chart
Replace U220
* TX not at talk-around frequency
June 1999