Motorola GP280

Troubleshooting Flow Chart for VCO 3-7
5.0 Troubleshooting Flow Chart for VCO
L3821,
L3822,
L3823,
O/C?
AUX 3 at
U3701
High?
U3801
Pin 19 =0V
AUX 3 at
U3701
High?
L3831,
L3832
L3833
O/C?
U3801
Pin 10
>1V?
Tx
Carrier?
VCTRL
0V or
13V?
START
No LO?
VCO OK
Check
R3829
TRB = 3.2V
Change L3831,
L3832
Change
U3801
Check U3701
Pin 2 for 3.2V
Change
U3701
Change
L3821,L3822,
L3823, L3825
Change
U3801
Change
U3801
Check for faulty parts
or dry joints of L3812,
C3806, R3806,
R3802, & L3801
A
A
No
No
Yes
Yes
Yes
No
No
Yes
Yes
Yes
No
Yes
No
No
Yes
Yes
No
No
Check R3811,
L3811 for dry
joint or faulty
No
Yes