Tx Or Rx Vco Unlock (Fail 001) (380–470 Mhz And 450–520 Mhz)—Part 2 Of 2 - Motorola ASTRO XTL 1500 Detailed Service Manual

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5.6.25 TX or RX VCO Unlock (Fail 001) (380–470 MHz and 450–520 MHz)—Part 2 of 2
3VDC
A
at pin 5 of
U5750?
Yes
Check 3 Volt
supply path from
Regulator U5750
Unlock
RX or
TX?
RX
Required
Aux pins
at 3.0VDC
for RX?
Yes
3.0VDC at
E6750?
Yes
Check U5753,
Q5708, Q5709,
and Q5710
Figure 5-27. TX or RX VCO Unlock (Fail 001) (380–470 MHz and 450–520 MHz)—Part 2 of 2
June 15, 2005
Check 5 Volt
No
supply path from
regulator U0505
Refer to Chart to determine
which AUX output determines
active VCO.
TX
No
Check
U5752
No
Check 3 Volt
supply path
Troubleshooting Charts: Flowcharts
Required
No
Aux pins
at 3.0VDC
for TX?
Yes
No
3.0VDC at
E6750?
Yes
Check
U5753, Q5706,
and Q5707
Check
U5752
Check 3 Volt
supply path
6815854H01-A