Motorola SSETM 5000 - Manual (Page 119)

6881094C12-A November 11, 2004
Troubleshooting Charts: VCO TX/RX Unlock 9-15
9.10 VCO TX/RX Unlock
MAEPF-27398-A
VCO TX/RX
unlock
<0.6Vdc
>11.0Vdc or
drifting?
3V at TP5?
Yes
Yes
Yes
Yes
Yes
No
No
No
No
Yes
Yes
Frequency
detected?
VCO locked?
No
Yes
No
5V at TP3?
Check
VOCON board
Check parts
around BJT. If
OK, replace BJT
Check control
voltage at
TP243
Check parts
around U1. If
OK, replace U1
Aux. line
4 high for TX
or low for RX?
No FET
drain voltage
0V?
Check parts
around FET. If
OK, replace FET
No
BJT
emitter voltage
>1.2V?
Check parts
around U250. If
OK, replace U250
Yes
No
Is pin
19 of VCOBIC
low for RX and
4.5 for TX?
Remove
VCO buffer
shield (SH302)
Check parts
around Q302. If
OK, replace Q302
Check parts
around U2. If
OK, replace U2
Remove
VCO shield
Check parts
around U202. If
OK, replace U202
"Sniff"
frequency near
VCO shield
Check if VCO
is locked using
spectrum analyzer
Sniff: Using an inductive field probe
as an antenna to measure
frequency. Place the probe
approximately 1/2 inch away
from components to be sniffed.
Q210 Q214
Field Effect Transistor (FET)
Q211 Q215
Bi-polar Transistor (BJT)