Localizing Problems; Table 4-12. Antenna Switch Dc Voltage Chart - Motorola ASTRO Digital Spectra Plus Detailed Service Manual

4-34
LOCATION
CR3920
CR3921
CR3922

4.5.1.2.3 Localizing Problems

Failure locations often can be determined by externally measured symptoms. Basic symptoms are
noted below with probable failure locations.
1. Low Power and High Current
- Check for improper load conditions caused by high VSWR external to the radio.
- Check output coax and mini-UHF connector.
- Check harmonic filter.
- Check output impedance-matching circuitry from the final device to the harmonic filter.
2. Low Power and Low Current
- If control voltage drive is equal to 9.2 V, then check per the above.
- If control voltage drive is less than 9.2 V, then check the control circuitry.
3. Power Intermittently Low (or Zero) and Current Less than 1 A. When Power Drops
- Check LLA stage.
4. Power Zero and Current Greater Than 3 A.
- Check harmonic filter, antenna switch, and matching circuits beyond final stage.
5. Power Zero and Current Between 1 and 3 A.
- Check driver and/or final stages.
6. Power Zero and Current Less Than 1 A.
- Check LLA/driver circuitry.
September 5, 2008

Table 4-12. Antenna Switch DC Voltage Chart

TYPICAL RX
ANODE 0
CATHODE 0
ANODE 0
CATHODE –
ANODE 0
CATHODE –
Troubleshooting Procedures: Power Amplifier Procedures
TYPICAL TX
NO PRE- COMMENTS
DRIVE
1.6
0.8
0.8
–
<0.8
–
6881076C25-E