Motorola HT Series Service Manual page 102


Yes
VCO is OK.
Check D201, D202,
C244, C245, C246 &
C247.
YES
5V
NO
Is U201 Pin 47
at pin 6 of
AT = 13 VDC
D201.
NO
Check
L200.
Check the 4.6V
biasing circuitry
and pin 28 of U201.
Troubleshoot the
Synthesizer.
No
No
Is pin 2
(AUX3) of
U201 high?
Is U201 Pin 28
Yes
at 4.6 VDC?
Check Q252 and
Q200.
YES
Replace U250.
No
Is RF level at
U201 Pin 32
Is the PRESC
as indicated?
RF level at
C227 as indi-
cated?
YES
Yes
Are
C226, R209,
R210, L204, C231,
Replace U250.
C801, C802, C803,
C804, C805, C225,
C218, R216, and
R217 OK?
YES
Replace U201.
Tx VCO OK.
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Is Tx signal Yes
present at the PA
driver IC, U101?
NO
Correct
Problem.
No
No
Is resonator
Resolder or
FL202
replace U206.
soldered
OK?
YES
Yes
Is
No
the 4.6V VSF
voltage present
at pins 3, 18, &
14 of U250?
Yes
Is TRB pin 19
of U250 high?
Yes
NO
Replace U201.
No
Is the 1.9V
present at
Replace U250.
R266 as indi-
cated?
Yes
If L203, C227 & C228
NO
are OK, then see VCO
Yes Is the steering
troubleshooting chart.
line voltage
VCTRL 0V or
13V?
No
No
Replace or
Is the Tx RF
NO
resolder
level at C254
defective
about 0dBm?
components.
Yes
Yes
No
Are the bias
Check Q251 and its
voltages of
Q251 as indi-
cated?
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START
Start
No
Is LO signal
present at the
mixer IC U301?
Visual
check of the
Board OK?
Resolder or
replace U205.
YES
YES
+5V at U201
NO
Pin's
13 & 30?
Check 5V
Regulator.
Are the
waveforms
at Pin's 14
&15 of U201
rectangular?
YES
Is there a short
NO
between Pin 47 and
Replace U250.
Pins 14 & 15 of
U201?
YES
Remove
Shorts.
bias circuitry.
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NO Check U24
3.3V at U201
pins 5, 20, 34
& 36.
YES
No
Is resonator
FL201 soldered
OK?
Is 16.8MHz NO
Signal at
U201 Pin 19?
Yes
YES
Is the 4.6V
VSF voltage
present at pins
Check Y201, C235,
3, 18, & 14 of
C237, C236, CR203
U250?
NO
Yes
Are Waveforms
at Pins 14 & 15
triangular?
Is TRB pin 19
YES
of U250 low?
NO
Yes
Check programming
lines between U409
No and U201 Pins 7,8 & 9. Is the 1.9V
present at
R265as indi-
cated?
NO
Yes
Check uP U409
Troubleshooting
Is the steering
Chart.
line voltage
VCTRL 0V or
13V?
No
Is the LO RF
level at C253
about 0dBm?
Yes
Are the bias
voltages of
Q304 as indi-
cated?
No
Check Q304 and its
bias circuitry.
L202.
Is
16.8MHz
Replace
signal at
U201.
U201 pin
YES
23?
NO
No
Check the 4.6V
biasing circuitry
and pin 28 of U201.
& R211.
Troubleshoot the
Synthesizer.
NO
No
Is pin 3
Do
No
(AUX4) of
Pins 7,8 & 9
U250 low?
of U201 toggle
when channel is
changed?
Yes
YES
Check Q252 and
Q200.
Is
Replace U250.
information
µ
from P U409
No
correct?
YES
Yes
Is the PRESC
RF level at
C227 as indi-
cated?
Replace U201
Yes
No
Replace U250.
Yes
Rx VCO OK.