Midland Syn-Tech III P25

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SYN-TECH III P25 PORTABLE RADIO

SERVICE MANUAL

6-13

ITEM DESCRIPTION QTY P/N

R83 RESISTOR TFMR SMD 0R 5% 0.063W 1 5905-4056-0000

SW1 SWITCH TACT SMD 1 5931-9989-9900

TD1 IC MAX7301AGL I/O QFN40 I 1 5961-5430-7301

TD2 IC OAM LMV321 SOT23-5 I 1 5961-5404-3210

TD3, 5 IC ASW SPDT SOT23-6 I 2 5962-5400-0001

TD4 AMPLIFIER 2X0.7W SSOP20 TDA8547I 1 5961-5430-8547

TD6 IC LVR TK112 SOT-23 5V 1 5961-5430-1250

TH1 THERMISTOR NTC SMD 47K 1 5905-5020-0473

TR1, 7, 8 TR NPN GNL BC847BT SOT416 3 5961-5521-0847

TR3, 4, 5, 6, 9, 10 TR NPN GNL BC847BT SOT416 6 5961-5521-0847

ZD1, 2 DIODE ZNR SMD I 2 5961-1375-0010

Reference Figure 6-5 and Figure 6-6.

Main Page

Table of Contents6
Definitions, Abbreviations and Acronyms8
Definitions8
Abbreviations and Acronyms8
Introduction11
General Features11
Technical Specifications12
Table 2-1: Syn-Tech III P25 Portable Radio General Specifications12
Table 2-2: Batteries for Syn-Tech III P25 Portable Radios12
Table 2-3: Syn-Tech III P25 Portable Radio Environmental Specifications12
Table 2-4: Syn-Tech III P25 Portable Radio Receiver Specifications13
Table 2-5: Syn-Tech III P25 Portable Radio Transmitter Specifications14
Description of the Radio15
Connection Diagram15
Figure 3-1: Midland Syn-Tech III P25 Portable Radio Connection Diagram15
Operating Principles16
RF and Control PCB16
Display and Keypad PCB18
Dsp Pcb18
Table 3-1: KN1, RF and Control PCB to DSP PCB Signals20
Table 3-2: KN2, RF and Control PCB to Display and Keypad PCB Signals21
Adjustment22
Definitions and Abbreviations22
Adjustment Conditions22
Adjustment Setup22
Table 4-1: Spurious Signal Frequencies22
Figure 4-1: Adjustment Setup23
Adjustment Procedures24
RF Output Power Adjustment24
Analog Frequency Adjustment 25 Khz24
Digital Frequency Adjustment24
Modulation Flatness Adjustment24
Modulation Limiting Adjustment25
FM Deviation Adjustment25
C4FM Deviation Adjustment25
Squelch Adjustment25
RSSI Adjustment26
C4FM Receive Level Adjustment26
Troubleshooting27
Table 5-1: Syn-Tech III P25 Portable Radio Error Messages27
Table 5-2: Syn-Tech III P25 Portable Radio Alert Messages28
Table 5-3: Syn-Tech III P25 Portable Radio 'Problem-Solution' Table29
Illustrated Part Lists31
Syn-Tech III P25 Portable Main Assemblies32
Figure 6-1: Main Assemblies Location Diagram32
Table 6-1: Main Assemblies Parts List33
Syn-Tech III P25 Portable Radio Pcb Assemblies34
Figure 6-2: PCB Assemblies Location Diagram34
Table 6-2: PCB Assemblies Parts List35
Syn-Tech III P25 Portable Radio Rear Panel Assembly36
Figure 6-3: Rear Panel Assembly Location Diagram36
Table 6-3: Rear Panel Assembly Parts List37
Syn-Tech III P25 Portable Radio Front Panel Assembly38
Figure 6-4: Front Panel Assembly Location Diagram38
Table 6-4: Front Panel Assembly Parts List39
Syn-Tech III P25 Portable Radio Display and Keypad Pcb Assembly40
Table 6-5: Display and Keypad PCB Parts List42
Syn-Tech III P25 Portable Radio Dsp Pcb Assembly44
Table 6-6: DSP PCB Parts List46
Syn-Tech III P25 Portable Radio Vhf Rf and Control Pcb Assembly47
Table 6-7: VHF RF and Control PCB Assembly Parts List49
Syn-Tech III P25 Portable Radio Uhf Rf and Control Pcb Assembly54
Table 6-8: UHF RF and Control PCB Assembly Parts List56
Disassembly and Assembly61
Required Equipment61
Usage62
Disassembling the Radio62
Disassembling the Pcb Assembly65
Schematic Diagrams68
UHF RF SCHEMATIC 450-512 Mhz68
Radio Connector Pinout69
Control Schematic73
Dsp Schematic74
Lcd and Keypad Schematic75

Midland Syn-Tech III P25 - Page 43

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