Tx Or Rx Vco Unlock (Fail 001) (700-800 Mhz)-Part 2 Of 2 - Motorola ASTRO Digital XTL 5000 Detailed Service Manual

Troubleshooting Charts: Flowcharts
5.6.43 TX or RX VCO Unlock (Fail 001) (700–800 MHz)—Part 2 of 2
3VDC
A
at pin 5 of
U6750?
Yes
Check 3 Volt
supply path from
Regulator U6750
Unlock
RX or
TX?
RX
Aux 3
or 4 at 3.0VDC
for RX?
Yes
8.2VDC
at TP6753 or
TP6751?
Yes
Check
U6755
Figure 5-45. TX or RX VCO Unlock (Fail 001) (700–800 MHz)—Part 2 of 2
6881096C74-B
Check 5 Volt
No
supply path from
regulator U0505
Refer to Chart to determine
which AUX output determines
active VCO.
TX
No
Check
U6751
Check
No
Q6756 or
Q6760
Aux 1
No
or 2 at 3.0VDC
for TX?
Yes
8.2VDC
No
at TP6767 or
TP6761?
Yes
Check
U6754
5-57
Check
U6751
Check
Q6767 or
Q6755
MAEPF-27818-O
May 25, 2005