Motorola HT1250-LS+ - Page 54

4-18 Maintenance
5V
at R203 &
R204
Is information
from
µP U409
correct?
Is U201 Pin
28 At 4.54
VDC?
Is U201 Pin
47 approx.
12.8VDC?
Is U241 Pin 19
<0.7 VDC in RX &
>4.3 VDC in TX?
Start
Visual
check of the
Board OK?
Correct
Problem
Check 5V
Regulator
U202
+5V at U201
Pin 30?
Is 16.8MHz
Signal at
U201 Pin 19?
Check Y200 and
assciated circuitry.
Are signals
at Pin’s 14 &
15 of U201?
Check
L201, etc.
Check Q202,
etc.
Is U201 pin 2 at
>3V in Tx and
<0.7V in Rx
Replace U201
Remove
Shorts
Is there a short
between Pin 47 and
Pins 14 & 15 of
U201?
Replace or
resolder
necessary
components
Is RF level at
U201 Pin 32
>-30 dBm?
Are R213-R215,
C241, C243-4, etc.
OK?
Replace U201
If L203, C234 & C235
are OK, then see VCO
troubleshooting chart
Are Waveforms
at Pins 14 & 15
triangular?
Do Pins 7,8 & 9
of U201 toggle
when channel is
changed?
Check programming
lines between U409
and U201 Pins 7,8 & 9
Replace U201
Check uP U409
Troubleshooting
Chart
NO
YES
NO
YES
NO
YES
NO
YES
NO
NO
NO
YES
YES
NO
YES
YES
NO
YES
YES
YES
NO
NO
NO
NO
YES
NO
YES
YES
Check CR201-2,
C223-5 and associ-
ated circuitry.
3.3V at U201
pins 5, 13, 20,
34 & 36
Check U203,
L202, etc.
Is
16.8MHz
signal at
U201 pin
23?
Replace
U201
YES
NO
NO
YES
NO
YES
Troubleshooting Flow Chart for Synthesizer