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BI-39175A
16
ADDITIONAL TOOLS REQUIRED
• RF Power Attenuator (30 dB, 150 watt, for transmitters with RF power beyond the capabilities of a Service
Monitor)
• Digital Voltmeter
• Oscilloscope (optional)
TRANSMITTER
SYMPTOM DIAGNOSTIC PROCEDURE
No RF power output. a. Program a Conventional System with frequencies given in Tables 2 and 3.
Use "EDACS3" PC Programming utility.
b. Check the RF Power Tracking Data, using "MRKMAINT" PC
Programming utility. The Data should be the same as that shipped with the
radio from the factory. I it has failed, re-enter the Tracking Data using the
procedure set forth in the "TRACKING DATA" section.
c. Check TP1 on the Power Amplifier PWB for A+. If it has failed, check the
power cable fuse.
d. Key the radio and measure the DC voltage at TP4 (9 VDC typical, when
keyed). If it has failed, trace TXENABLE signal back to Logic PWB.
e. Unscrew the PA module from the rest of the radio unit. Remove P1 from
J151, and connect an RF wattmeter to J151. Be sure to AC couple J151 to
the wattmeter. Key the radio and measure the exciter power at J151.
Power should be 400-700 mW. If it has failed, replace the Synthesizer
PWB, and reload the Modulation Tracking Data. If this passes, replace the
PA PWB.
Frequency too low/high. Adjust XU201 on the Synthesizer PWB. If the frequency is still out of
specification, replace the Synthesizer PWB.
Low or no modulation. a. Program a Conventional System with frequencies given in Tables 2 and 3.
Use "EDACS3" PC Programming utility.
b. Check the Modulation Tracking Data, using "MRKMAINT" PC
Programming utility. Data should be the same as that shipped with the radio
from the factory. If this has failed, re-enter the Tracking Data using the
procedure set forth in the "TRACKING DATA" section.
c. Apply a 1000 mVRMS, 1 kHz audio signal to the MIC connector Pin 1
(Pin 2 is ground reference). Key the radio (make sure the antenna
connector is connected to the proper 50 ohm load). Check for an audio
signal at TP202 on the Synthesizer PWB. If this has failed, replace the
Logic PWB. Be sure to perform the complete re-programming on the new
Logic PWB, If this passes, replace the Synthesizer PWB, and re-load the
Modulation Tracking Data.