Motorola P100 Series Detailed Service Manual

9-2 VHF Troubleshooting Tables: Troubleshooting Table for Synthesizer (VHF)
9.2 Troubleshooting Table for Synthesizer (VHF)
Table 9-2. Troubleshooting Table for Synthesizer (VHF)
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