Motorola P100 Series Detailed Service Manual

12-2 UHF1 Troubleshooting Tables: Troubleshooting Table for Synthesizer (UHF1)
12.2 Troubleshooting Table for Synthesizer (UHF1)
Table 12-2. Troubleshooting Table for Synthesizer (UHF1)
Symptom Possible Causes Procedure Corrective Action
Synthesizer Out of
Lock (No RX
Mode)
1. Defective 12.8 MHz
VCTCXO
Verify clock output FL701 Pin 3 is
12.8 MHz using high impedance
probe.
Repair/Replace FL701
2. 1/2VCC defective Verify FL701 Pin 1, U502–B Pin 5 &
U502–D Pin 14 voltage is 1.9V.
Troubleshoot: 1/2VCC circuitry
3. No RX–Enable Verify U101 Pin 71 (RX–EN1) is
high.
Verify Q304 collector voltage is
approximately 4.7V in RX mode
Check U101 operating
Troubleshoot: Q304 & Q305
circuitry
4. Check PLL–LD port Verify U101 Pin 27 is Low (Normal
Mode)
Verify U101 Pin 27 is swept from low
to high (Power Save Mode)
Troubleshoot: PLL circuitry.
Repair/Replace U701
Synthesizer Out of
Lock (No TX Mode)
1. Defective 12.8 MHz
VCTCXO
Verify clock output FL701 Pin 3 is
12.8 MHz using high impedance
probe.
Repair/Replace FL701
2. 1/2VCC defective Verify FL701 Pin 1, U502–B Pin 5 &
U502–D Pin 14 voltage is 1.9V.
Troubleshoot: 1/2VCC circuitry
3. No TX–Enable Verify U101 Pin 84(TX–EN1) is high
when PTT is pressed.
Verify Q407 collector voltage is
approximately 4.7V when PTT is
pressed (TX–EN2).
Check U101 operating
Check U101–Pin 85 is high/
Replace Q407/check LK2 is
short
4. Check PLL–LD port Verify U101 Pin 27 is Low (Normal
Mode)
Verify U101 Pin 27 is swept from low
to high (Power Save Mode)
Troubleshoot: PLL circuitry
Repair/Replace U701
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Motorola P100 Series Specifications

General

Brand	Motorola
Model	P100 Series
Category	Portable Radio
Language	English