2-1
Section 2
THEORY OF OPERATION
1.0
Introduction
This Chapter provides a detailed theory of operation for the Controlhead circuits. For details of the
trouble shooting refer to the related Section of this manual.
2.0
Controlhead Model for GM328
The controlhead contains the internal speaker, the On/Off/Volume knob, the microphone connector,
several buttons to operate the radio and several indicator Light Emitting Diodes (LED) to inform the
user about the radio status. To control the LED’s and to communicate with the host radio the control-
head uses the Motorola 68HC11E9 microprocessor.
2.1
Power Supplies
The power supply to the controlhead is taken from the host radio’s FLT A+ voltage via connector
J0801 pin 3 and the reg5V via connector J0801 pin 7. The voltage FLT A+ is at supply
voltage level and is used for the LED’s, the back light and to power up the radio via on / off / volume
knob. The stab5 volt is used for the microprocessor and the keypad buttons. The voltage
USW 5V derived from the FLT A+ voltage and stabilized by the series combination of R0822,
VR0822 is used to buffer the internal RAM of the microprocessor (U0831). C0822 allows the supply
voltage level to be disconnected for a couple of seconds without losing RAM parameters. Dual diode
D0822 prevents radio circuitry from discharging this capacitor. When the supply voltage is applied to
the radio, C0822 is charged via R0822 and D0822. To avoid, that the µP enters the wrong mode
when the radio is switched on while the voltage across C0822 is still too low, the regulated 5V charge
C0822 via diode D0822.
2.2
Power On / Off
The On/Off/Volume knob when pressed switches the radio’s voltage regulators on by connecting line
ON OFF CONTROL to line UNSW 5V via D0821. Additionally, 5 volts at the base of digital transistor
Q0822 informs the controlhead’s microprocessor about the pressed knob. The microprocessor
asserts pin 62 and line CH REQUEST low to hold line ON OFF CONTROL at 5 volts via Q0823 and
D0821. The high line ON OFF CONTROL also informs the host radio, that the controlhead’s
microprocessor wants to send data via SBEP bus. When the radio returns a data request message,
the microprocessor will inform the radio about the pressed knob. If the radio was switched off, the
radio’s µP will switch it on and vice versa. If the On/Off/Volume knob is pressed while the radio is on,
the software detects a low state on line ON OFF SENSE, the radio is alerted via line ON OFF
CONTROL and sends a data request message. The controlhead µP will inform the radio about the
pressed knob and the radio’s µP will switch the radio off.
Summary of Contents for GM338
Page 1: ...GM328 GM338 GM398 Mobile Radios Detailed Service Manual 6804112J18 E December 2003 ...
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Page 7: ...GM328 GM338 GM398 Mobile Radios Service Maintainability Issue December 2003 ...
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Page 20: ...1 4 Radio Model Information THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 32: ...2 12 Notes For All Schematics and Circuit Boards THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 35: ...GM328 GM338 GM398 Mobile Radios Controlhead Service Information Issue December 2003 ...
Page 42: ...1 4 GM398 Model GCN6115_ THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 56: ...2 14 Controlhead Model for GM398 THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 70: ...4 2 Allocation of Schematics and Circuit Boards THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 88: ...4 20 Controlhead GM398 PCB 8486178B03 Schematics THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 89: ...GM328 GM338 GM398 Mobile Radios Controller Service Information Issue December 2003 ...
Page 114: ...2 2 Controller Troubleshooting Chart THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 140: ...3 26 Controller T7 T9 Schematic Diagrams THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 141: ...GM328 GM338 GM398 Mobile Radios VHF 136 174MHz Service Information Issue December 2003 ...
Page 148: ...1 4 Technical Specifications THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 158: ...2 10 VHF 136 174 MHz Frequency Synthesis THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 166: ...3 8 Troubleshooting Flow Chart for VCO THIS PAGE INTENTIONALLY LEFT BLANK ...
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Page 186: ...4 20 VHF 1 25W PCBs Schematics Parts Lists THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 187: ...GM328 GM338 GM398 Mobile Radios UHF 403 470MHz Service Information Issue December 2003 ...
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Page 235: ...GM328 GM338 GM398 Mobile Radios UHF Band 2 450 527MHz Service Information Issue December 2003 ...
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Page 275: ...GM338 GM398 Mobile Radios Low Band Service Information Issue December 2003 ...
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Page 284: ...1 4 Technical Specifications THIS PAGE INTENTIONALLY LEFT BLANK ...
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Page 379: ...GM338 Mobile Radios VHF 45W Bipolar 136 174MHz Service Information Issue December 2003 ...
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Page 411: ...GM338 Mobile Radios UHF1 40W Bipolar 403 470MHz Service Information Issue December 2003 ...
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Page 447: ...GM338 Mobile Radios UHF2 40W Bipolar 450 520MHz Service Information Issue December 2003 ...
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Page 482: ...4 14 UHF Band 2 25 40W PCB Schematics Parts List THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 483: ...GM338 Mobile Radio UHF B1 HIGH POWER LDMOS 403 470MHz Service Information Issue December 2003 ...
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