6881076C25-E September 5, 2008
Troubleshooting Procedures: Power Amplifier Procedures 4-75
6. Power-Leveling Circuitry Test
With the radio connected for power measurements, vary the line voltage from 12.5 to 16 V.
The power should not vary more than 3 Watts. At a line voltage of 13.6 V, vary the frequency
using the three test modes. If power varies more than 3 Watts, measure the detected voltage
on P0853, pin 9. If this voltage varies more than 0.2 V over line and frequency variations, the
power control circuitry (most of which is located on the command board) may be
malfunctioning. If the detected voltage varies less than 0.2 V, the problem is likely in CR9900,
the harmonic filter, the antenna switch, or the output coax. Check continuity through 12 pin
DC connector P0853 on the PA board; check digital/analog circuitry, and check 5-V regulator
operation. See Table 4-24 on page 4-68 for typical values.
NOTE: If any part of the power leveling circuitry is replaced, perform the power set procedure. See
the ASTRO Digital Spectra and Digital Spectra Plus Mobile Radios Basic Service Manual
(6881076C20) for details.
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