Troubleshooting Table For Synthesizer (Uhf2); Table 6-2. Troubleshooting Table For Synthesizer (Uhf2) - Motorola P100 Series Detailed Service Manual

6-2
6.2

Troubleshooting Table for Synthesizer (UHF2)

Symptom Possible Causes
Synthesizer Out of 1. Defective 12.8 MHz
Lock (No RX VCTCXO
Mode)
2. 1/2VCC defective
3. No RX-Enable
4. Check PLL-LD port
Synthesizer Out of 1. Defective 12.8 MHz
Lock (No TX Mode) VCTCXO
2. 1/2VCC defective
3. No TX-Enable
4. Check PLL-LD port
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UHF2 Troubleshooting Tables: Troubleshooting Table for Synthesizer (UHF2)

Table 6-2. Troubleshooting Table for Synthesizer (UHF2)

Verify clock output FL701 Pin 3 is
12.8 MHz using high impedance
probe.
Verify FL701 Pin 1, U502-B Pin 5 &
U502–D Pin 14 voltage is 1.9V.
Verify U101 Pin 71 (RX-EN1) is high.
Verify Q304 collector voltage is
approximately 4.7 V in RX mode
Verify U101 Pin 27 is Low (Normal
Mode)
Verify U101 Pin 27 is swept from low
to high (Power Save Mode)
Verify clock output FL701 Pin 3 is
12.8 MHz using high impedance
probe.
Verify FL701 Pin 1, U502-B Pin 5 &
U502-D Pin 14 voltage is 1.9 V.
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).
Verify U101 Pin 27 is Low (Normal
Mode)
Verify U101 Pin 27 is swept from low
to high (Power Save Mode)
Procedure
Repair/Replace FL701
Troubleshoot: 1/2VCC circuitry
Check U101 operating
Troubleshoot: Q304 & Q305
circuitry
Troubleshoot: PLL circuitry.
Repair/Replace U701
Repair/Replace FL701
Troubleshoot: 1/2VCC circuitry
Check U101 operating
Check U101-Pin 85 is high/
Replace Q407/check LK2 is
short
Troubleshoot: PLL circuitry
Repair/Replace U701
Corrective Action