Motorola Astro XTL 1500 - TX or RX VCO Unlock (Fail 001) (700-800 Mhz)-Part 2 of 2

June 15, 2005 6815854H01-A
5-54 Troubleshooting Charts: Flowcharts
5.6.43 TX or RX VCO Unlock (Fail 001) (700–800 MHz)—Part 2 of 2
Figure 5-43. TX or RX VCO Unlock (Fail 001) (700–800 MHz)—Part 2 of 2
MAEPF-27818-O
Check 3 Volt
supply path from
Regulator U6750
Refer to Chart to determine
which AUX output determines
active VCO.
3VDC
at pin 5 of
U6750?
No
Check 5 Volt
supply path from
regulator U0505
Unlock
RX or
TX?
TX
RX
Yes
Aux 3
or 4 at 3.0VDC
for RX?
No
No
Yes
Check
U6751
Check
U6755
8.2VDC
at TP6753 or
TP6751?
Yes
Check
Q6756 or
Q6760
Aux 1
or 2 at 3.0VDC
for TX?
No
No
Yes
Check
U6751
Check
U6754
8.2VDC
at TP6767 or
TP6761?
Yes
Check
Q6767 or
Q6755
A