UHF/VHF FM TRANSCEIVER PX-777/328/338

SERVICE MANUAL

------------------CONTENTS-------------------------INTRODUCTION2 GENERAL... 2 REALIGNMENT.3 TROUBLE SHOOTING GUIDE6 TECHNICAL SPECIFICATION.. 7 FUNCTION SPECIFICATION.8 CIRCUIT DESCRIPTION.. 9 SEMICONDUCTOR DATA... 16 PARTS LIST... 17 BLOCK DIAGRAM.. 22 PCB BOARD23 SCHEMATIC DIAGRAM.. 25

INTRODUCTION

SCOPE OF THIS MANUAL This manual is intended for use by experienced technicians familiar with similar types of commercial grade communications equipment. It contains all required service information for the equipment and is current as of the publication data. Changes which may occur after publication are covered by either Service Bulletins or Manual Revisions. These are issued as required.
ORDERING REPLACEMENT PARTS
When ordering replacement parts or equipment information, the full part identification number should be included. This applies to all parts : components, kits, or chassis. If the part number is not known, include the chassis or kit number of which it is a part, and a sufficient description of the required component for proper identification.

PERSONNEL SAFETY

The following precautions are recommended for personnel safety: DO NOT transmit until all RF connectors are verified secure and any open connectors are properly terminated. SHUT OFF and DO NOT operate this equipment near electrical blasting caps or in an explosive atmosphere. This equipment should be serviced by a qualified technician only.

SERVICE

This radio is designed for easy servicing. Refer to the schematic diagrams, printed circuit board views, and alignment procedures contained within.

GENERAL

Your Transceiver is an electronic product of exact design and should be treated with care.The suggestions below will help you to fulfill any warranty obligations and to enjoy this product for many years. Do not attempt to open the unit. Non-expert handling of the unit may damage it. When using regulated power supply, take notice of power voltage must be between 6V and 8V to avoid damaging the unit. Do not store the Radio under the sunshine or in hot areas. High temperatures can shorten the life of electronic devices, and warp or melt certain plastics. Do not store the Radio in dusty, dirty areas Keep the Radio dry. Rainwater or damp will corrode electronic circuits. If it appears that the Radio diffuses peculiar smell or smoke, please shut off its power immediately and take off charger or battery in the Radio, then contact with PUXING agency. Do not transmit without antenna.

REALIGNMENT

1. MODE:
USER MODE: For normal use, when turn on enter this mode. PC MODE: used to read and program radio. SELF-PROGRAMMING MODE: Hold down [MONI] and [menu] key accomplished by turning on the VOL/POWER switch until SELF displays.

2. LCD DISPLAY

3. SELF-PROGRAMMING MODE
For frequency,signal,feature write to the radio

TECHNICAL SPECIFICATION

General Frequency Range Working Temperate Operating Voltage Operate Mode Channel spacing Dimension Weight Antenna impedance Transmitter Frequency Stability Output Power Max Frequency Deviation Audio Distortion Modulation Character Adjacent Channel Power Spurious Radiation Occupied Bandwidth Receiver RF Sensitivity Audio Distortion Audio Response Adjacent Channel Selectivity Intermodulation Rejection Spurious Response Blocking 136 174MHz 350 390MHz 400 470MHz,245Mhz 2050 DC 7.2V Simplex or Semi-duplex 25Khz/12.5Khz 100mm55mm32mm (Not included Antenna) 220g (Including battery) 50
2.5PPM 5W/4W 0.5W 5KHz 3% +3dB-3dB 65dB 7.5UW 16KHz
0.2UV 3% +2dB-10dB 60dB 60dB 60dB 80dB
CPU PIN FUNCTION ITEM DESCRIPTION 1 CLK ROM 2 DDDDPLL CS 7 LAMPKKKKAVDD 13 RXRXTXTXBEEP/QT 18 ACC 19 AVSS 20 APC/TUNE 21 AT X 22 AR X 23 BATT Test 24 VOX 25 AN SQL 26 OSCin 27 OSCout 28 VSS 29 ENENMONI 32 Reset 33 Vdd 34 5TC 35 LED G 36 TXD/LED R 37 AFC 38 5CC 39 P-AMP 40 N/W/LD 41 PTT/RX D 42 HT1621 CS 43 LAMPDQT

PX-777 I/O I/O O O O O O O I I I I O I I O O FUNCTION CLOCK AND EEPROM Key scan output Key scan output PLL clock port/Key scan output PLL data port/Key scan output PLL CS port Lcd/backlight control output Key scan input Key scan input Key scan input Key scan input MPU+5MV IF output control port IF input control port MIC input control port MIC output control port BEEP output /CCTCS tone signal output MPU power filter Connect to VSS Automatic power &frequency automatic gain output Transmitter data output select control Receiver data input/audio amplifier adjustment input Battery check /Reset VOX input Squelch signal input port Internal oscillator input Internal oscillator output GND Encoder data input Encoder data input Monitor key input CPU reset port +5V power supply TX power supply control output LED green RX232 output/ LED red Audio amplifier control input Power supply control output Audio amplifier power supply control output Unlock detection PTT key input/RX232 input LCD CS port Backlight control output DTC audio signal output
O O I O I I I O I I I I O O O O O O O I I O O
PX777 part list(136-174MHz)
Footprint C0402 C0402 C0402 C0402 Comment Quantity 0.5P 1P 1.5P 100P C332 C231 C346 C423 C535 C416 C387_1 C121 C156 R808 C123 C413 C623 C450 C174 C668 C514 CAP C411 C663_1 C103 C182 CAP C201 C517 C263 C348 C259 C224 C113 18NH C327 C264 C591 C272 C421 C256 C353 C414 C134 C426 C516 C349

Designators

C456 C536 C415 C318_1 C132 C223 C386_1 C455 C269 CAP C665_1 C181 C454 C392 CAP C453
C0402 C0402 C0402 C0402 C0402 C0402 C0402 C0402 C0402 C0402 C0402 C0402 C0402 C0402 C0402 C0402
105P 10P 120P 12P 15P 18P 1P 220P 222P 223P 224P 22P 273P 27P 332P 333P
C315 C317_2 C313_2 C175 C537 C538 C315_2 C314_2 CAP CAP C593 CAP C316_2 C312_2 C326_1 C227 C135 C133 C142 C144 C222 C322 C612 CAP C146 C145 C176 C122 C515 C254 C610 C451 C633 C529 C528 C613 C105 C581 C520 C701 C244 C247 C321 C351 C621 CAP C594 C301 C391 C257 C268 C266 C267 C202 C203 C561 C271 C388_1 C319_1 C250 CAP C101 C573 C571 C511 C521 C208 C316 CAP C354 C662 C302 C418 C102 C147 C661 C131 C611 C609 C664 C255 C361 C363 C362 C213 C330 C331 C241 C523 C265 C359 C246 C329 C394

C556 C432

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R122 330R

R392 120K

C391 102P

L392 22nH

C127 470P R124

R127 47K

R126 22R

R136 47R T141 2SK3476 C141 NC

L143 8T

C145 104P

C146 103P

C396 102P R398 0R R399 3K3 C390 NC D111 HSC277 C111 470P
R153 0R C151 1P C152 22P C153 NC

T392 2SC3356

C397 P C398 102P

T111 2SC3356

T121 2SC4988 R115 680R R121 22R

C123 6P

10R C124 104P

C125 470P C129 N.U.

R125 0R C126 N.U.

C135 N.U.

C136 NC

C121 470P

D213 HSC277 5C 5T 5V R256 18K C256 103P C201 103P T201 DTA114EE
T301 DTA114EE C302 103P R301 1K C303 470P
BATT 5V C181 102P E181 4.7uF (T.Y.) C173 103P R195 150K

5V C301 103P

5VOX C412 103P C416 R413 5K6 R414
3.58MHz R537 1M C537 5CC R408 C410 103P R409
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P_TX 5T R138 47K L142 101T C144 470P R158 270R C143 103P L143 8T C145 104P C146 103P C158 NC R153 C141 NC 0R C151 1P C152 22P C153 NC C154 15P C157 470P C156 C155 27P 7P R157 270R L157 220nH D156 HVU131 C162 470P C161 3P L211 4T R211 0R D212 HSC277 BATT D211 HSC277 C211 2P L161 4T C163 10P C166 2P L162 4T C164 9P C167 5P L163 3T C165 10P C168 3P C169 1.5P L164 1uH ANT111 ANT

C142 1uF

R136 47R T141 2SK3476
5T 5V T201 DTA114EE C201 103P C101 104P T103 2SB624 R101 4K7 T102 DTA114EE
BATT 5T C401 103P C444 104P R443 1M8 R442 33K C442 332P T431 2SK1824 R438 100R R401 470R C416 R413 5K6 R414 E401 4.7uF

5VOX C412 103P