Troubleshooting Table For Synthesizer (Uhf1); Table 12-2. Troubleshooting Table For Synthesizer (Uhf1) - Motorola P100 Series Detailed Service Manual

12-2

12.2 Troubleshooting Table for Synthesizer (UHF1)

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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UHF1 Troubleshooting Tables: Troubleshooting Table for Synthesizer (UHF1)

Table 12-2. Troubleshooting Table for Synthesizer (UHF1)

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 4.7V 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 1.9V.
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