Ericsson EDACS 19D902120G1 Maintenance Manual Download Page 1 | Manualshive

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Printed in U.S.A

LBI-38163B

ERICSSONZM

ERICSSONZM

Ericsson GE Mobile Communications Inc.

Mountain View Road Lynchburg Virginia 24502

EDACS

®

900 MHz TRUNKED RECEIVER
19D902120G1

Mobile Communications

Maintenance Manual

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Summary of Contents for EDACS 19D902120G1

Page 1: ... in U S A LBI 38163B ERICSSONZM ERICSSONZM Ericsson GE Mobile Communications Inc Mountain View Road Lynchburg Virginia 24502 EDACS 900 MHz TRUNKED RECEIVER 19D902120G1 Mobile Communications Maintenance Manual ...

Page 2: ...four counter U9 The counter output is applied to phase detector U10 whose output is applied to DC amplifier U11 Feedback for the loop control voltage is developed across R7 The 70 450 MHz output is coupled through C40 from the collector of Q4 to pin 4 of audio IC U6 where it is mixed with the 70 MHZ 1st IF input to derive the 455 kHz 2nd IF Second Mixer IF Audio Integrated circuit IC U6 contains t...

Page 3: ...4 The discriminator output is connected through J601 3 on the audio board Power is supplied from a regulated 10 volts from the system board A Block Diagram Of the audio board is shown in Figure 2 Audio Preamplifier Discriminator audio from J602 3 is coupled through Audio Level Adjust R608 to the preamplifier circuit The preamp con sists of Q601 Q602 Q605 and associated circuitry and provides 26 dB...

Page 4: ...the squelch circuit to prevent squelch closing on weak signals When the receiver is quieted by an on frequency signal receiver unsquelches the voltage at U603D 10 rises to ap proximately 5 Volts DC and the output at pin 14 drops to near 0 volts This turns on the audio stages and sound is heard at the speaker RUS Switch Receiver Unsquelched Sensor When the receiver is unsquelched the output of the ...

Page 5: ...put when unsquelched increases the gain of the noise amp ppreventing squelch closing on weak signals The RUS output at U603 8 is also connected to the system board through P904 8 for use in special applications CAS Switch Carrier Activity Sensor The squelch in U603 also drives the CAS switch in the IC When the receiver unsquelches the voltage at U603 6 rises to approximately 10 volts This voltage ...

Page 6: ...ust Z1 counter clockwise until the audio level drops 1 dB Audio Board System Audio Level Adjust R608 1 Apply a 50 dBm RF signal with 1 kHz at the receiver input 2 Adjust R608 for a reading of 1 volt RMS at P904 11 Volume Squelch High Squelch Noise Calibration 1 Turn the SQUELCH control on the exciter receiver door fully clockwise Then turn the control counterclockwise approximately one third of th...

Page 7: ... GREASE BETWEEN U8 AND BOARD ITEM 2 PER PROCESS 19A701431 P6A EA11 THE FOLLOWING ITEMS ARE MOS DEVICES REQUIRING SPECIAL CARE PER 19A701294 Q3 19D902083 Sh 1 Rev 3 19A705498 Sh 1 Rev 3 19D902083 Sh 2 Rev 3 19A705498 Sh 2 Rev 3 TOP VIEW BOTTOM VIEW LBI 38163 6 ...

Page 8: ...SCHEMATIC DIAGRAM RECEIVER BOARD 19D902083G1 19D902107 Sh 1 Rev 4 LBI 38163 7 ...

Page 9: ...SCHEMATIC DIAGRAM AUDIO BOARD 19D902181G1 19D902181 Sh 1 Rev 0 19D902182 Sh 1 2 Rev 3 LBI 38163 8 ...

Page 10: ...SCHEMATIC DIAGRAM AUDIO BOARD 19D902181G1 19D902183 Sh 1 Rev 1 LBI 38163 9 ...

Page 11: ...OUTLINE DIAGRAM AUDIO BOARD 19D902093G1 19D902093 Sh 1 Rev 0 19A705508 Sh 1 2 Rev 0 LBI 38163 10 ...

Page 12: ...SCHEMATIC DIAGRAM AUDIO BOARD 19D902093G1 19D902112 Sh 1 Rev 1 LBI 38163 11 ...

Page 13: ...PARTS LIST LBI 38163 12 ...

Page 14: ...PARTS LIST LBI 38163 13 ...

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