Tx Or Rx Vco Unlock (Fail 001) (136-174 Mhz)-Part 2 Of 2 - Motorola ASTRO Digital XTL 5000 Detailed Service Manual

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5.6.10 TX or RX VCO Unlock (Fail 001) (136–174 MHz)—Part 2 of 2
3VDC
A
at pin 5 of
U3750?
Yes
Check 3 Volt
supply path from
Regulator U3750
Unlock
RX or
TX?
RX
Aux 3
or 4 at 3.0VDC
for RX?
Yes
8.2VDC
at TP6761 or
TP6763?
Yes
Check components
around Q3751 or
Q3752, if OK,
replace Q3751 or
Q3752 respectively
Figure 5-14. TX or RX VCO Unlock (Fail 001) (136–174 MHz)—Part 2 of 2
May 25, 2005
Check 5 Volt
No
supply path from
regulator U0505
Refer to Chart to determine
which AUX output determines
active VCO.
TX
No
Check
U3751
Check
No
Q3766 or
Q3764
Troubleshooting Charts: Flowcharts
Aux 1
No
or 2 at 3.0VDC
for TX?
Yes
8.2VDC
No
at TP6772 or
TP6760?
Yes
Check components
around Q3753 or
Q3754, if OK,
replace Q3753 or
Q3754 respectively
Check
U6751
Check
Q3765 or
Q3763
AEPF-27818-O
6881096C74-B