PX-1000 PXP40 - Crypto Museum
Contents
1. HYBRID TYPE TH536 ON LOGIC BOARD H Component transistor transistor diode zener diode capacitor resistor Type NPN PNP l ur 3 3nF 0 luF 13 800 1 K 3 K 3 3K 4 7K 10 K 22 K 30 K 45 K 53 K 68 K 70 K 82 K 90 K 100K 150K 180K 470K 600K 750K 3 M Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm Ohm TI T3 T8 T10 T4 T7 T9 T11 T13 D2 D13 Z1 2 C4 17 C18 C25 R37 R22 R8 18 34 R46 R26 28 R42 R19 20 21 23 24 25 27 40 R39 41 R15 R10 R13 R45 R16 R17 R11 R3 5 6 7 9 R4 R14 R44 R12 R43 R38 Qnty on Hybrid bo pwa ND Q f jann pat Ker pet pent pant pen CF beat kend k be Kek ke OO 2452 KEYBOARD A160 4D P N Type No 1405 IN4148 646 4K7 Ohm 2 2uH 1020 560pF 2001 D101631C 2011 HS J0861 01 240 2013 HS J0838 MI SCELANEOUS 1901 M4031 3 7001 2402 70515 Description Comp No diode DI D9 LED D10 resistor RI R16 RF choke LI L6 ceramic cap Cl C4 32 way plug J1 socket 3 5 mm stereo J3 socket 2 5 mm mono J4 LCD module flexible PCB J2 driver speaker microphone battery package BI i 46 Qty per unt 9 i 16 7 6 2 4 3 ad ABA BA Ss d A jew pwent jd ra 3 SECTION B PXP40 CONTENTS 12. LCD MODULE 40 CHARACTER DISPLAY A 6 LCD DRIVERS KEY BOARD ASSY SEMAR OUT amp ROU DO ON STOP KEY 12 VDC n be y MIC SPEAKER AUX PORT CHAPTER 3 SERVICE 3 1 DISASSEMBLY OF PX1000 The PX1000 can be dismantled for repair and adjustment purposes as follows 1 Remove bottom housing by first unscrewing the six self tap cross head screws on the underneath side of the unit Separate the bottom housing from the remainder of the unit by first lifting the end nearest the audio socket J4 and then sliding the other end from around the power socket J3 Disconnect the battery pack speaker from the main circuit by slipping socket J5 from plug J5 on the logic board The battery pack is fixed to the bottom housing with adhesive but can be easily removed for replacement purposes The speaker sits in a groove in the rubber sealing ring and be eased out with the aid of a small flat top screwdriver or similar tool Desolder the wires from the speaker to seperate it completely from the unit The rubber accoustic sealing ring can be removed by slipping it through the hole in the housing Remove the logic board from the keyboard LM assembly by separating 32 pin socket JI on the logic board from the 32 pin plug Jl on the keyboard PCB using a small flat head screw driver To access the LCD module first remove the instruction sticker from the LCD cover Unscrew the nine c
3. ES i NITAL OL ATISIS z E Kerar DIAZI L 3240023 VOLE L23NN03 INIDYVH LON AYILLVG Eos os tes So ft tos te Es Ea Es Ecs gt amp Es Es Eos Er Eo Co ES ET ES ES A Em AP ET ET Em Em INAGIZONI HlVdI 04000 2 907 6 l A i A2 IIVIA FIY SNOILIINNOI 72722 YivITY a YIVITS Yo SOS ANE OL SI EMP OL EM Woes SNG SSTYOQVNIINI afe YIVITY La VOS MI EMC 191 SAG YLVI Word SNNOJ WIIND d 22 Moyy 12 Ohd LIINNOISIO itis 77437 oor pa 45 78275 J E 24 Woe FIVIAIY 21 wWVY IIV Ae ZA 2 doLS NO SSIYd AV 74 SII NO NS 99NY ASAIN ALTAVA dd vog LSFL ET ET ES f 86020 12 864 JOVE NIMLIQ 2902 YIIHIA 077 OL YIMOd XITHD xo Ir E N d ou Inti Af NILVI YO ZA TYVALIOS YILVI MLIA SIUYVOG 9a DIGITAL FAULT REPAIR Faults in the digital side of the circuit are much more difficult with which to cope Such problems are recogniseable by the resultant rubbish that appears on the display either in the form of a complete black or blank display or random characters anywhere on the display Because all the individual parts of the digital cct are inter linked such a symptom could indicate a fault with any one or more of these parts Therefore some strategy needs to be adopted that will pin point the actual fault Basic essentials
4. GENERAL 1 1 Product Description 1 2 Specifications 2 THEORY OF OPERATION 3 SERVICE 3 1 Disassembly assembly 3 2 Test Procedure 3 3 Repair 4 APPENDICES 4 1 Component Listing 4 2 Component Layout Diagram 4 3 Circuit Schematics 49 50 50 51 52 56 56 57 58 60 60 62 62 50 CHAPTER 1 GENERAL 1 1 PRODUCT DESCRIPTION The TEXT TELL PXP40 is a compact 40 column dot matrix thermal transfer printer developed mainly for use with the PX1000 pocket telex Printing is onto a roll of thermal sensitive paper which can be cut after each print out by means on an in built paper cutter The character font is made up of 7 x 5 dot The unit is fully portable and operates from an internal rechargeable battery pack The housing includes two sping clips to enable the unit to be firmaly attached to the PX1000 Data transfer to the printer is serial The PXP has two terminals one for the 12V DC adapter and one which serves two functions as a serial port and as a 12V ouput for charging the PX1000 2 3 2 La LA 3 a3 73 3 Ta Ta Ca T3 3 a Ta 3 Pg ai A Fa FA en 1 2 SPECIFICATIONS General Dimensions Lenght Weight Height Weight Technical Power Supply Power consumption Battery charge current Battery use after full charge Buffer memory capacity Printing speed Serial Port Baud rate Data format Parity Voltage levels input output
5. between the locations 0000 to 3FFF Power to the RAM IC is fed directly from the battery voltage to VDD pin 28 via diodes D3 and D4 This ensures that RAM cotents are saved for as long as the battery voltage remains above 5 9 V theoretically In actual practice the contents remain valid for much lower voltage levels Because of the low current consumption of the IC in standby resistor RI7 ensures that diodes D3 and D4 are turned on fully to provide the required voltage drop from the battery voltage Capacitor C24 provides power supply decoupling 10 KEYBOARD The keyboard is included on the memory map but is enabled seperately by the MPU via output P16 The keyboard is read in the following manner First a quick scan is made to determine whether a key has been pressed This involves enabling the keyboard by bringing P16 low If no key is pressed all data lines will be high A pressed key will cause one data line to go low via a combination of two of resistors Ri to RI6 To identify exactly which key has been pressed each address line AO to A8 is brought low individually and the data bus read as above LOM The Liquid Crystal Display Module the L M is custom designed for the PX1000 It is a one line X 40 character display each character contained in a 5 x 7 dot font Also on the display are up to seven miniature fixed messages which are used to indicate the status of certain functions to the user The LCM is driven
6. but the BUSY READY at connector 3 is not then there is a fault in the circuit involving 12 T3 T5 and Tili When pin 24 101 is high all transistors should be on When this pin is low only T2 should on If this is not so replace the the suspect transistor If the printer still loses some of the message it might be that the RAM IC2 is faulty Replace this and check again 3 NO PRINT Check that data is entering the MPU ICI pin 6 when PRINT on the PX is pressed and the printer is not busy If there is no data entering but data is present at the input on connector 3 then check for open or short circuits between the connector and pin 6 ICI If none found replace T4 Check the motor on off signal from ICI1 pin 23 When this pin is low the motor should be on If not check the connections from the motor to the main PCB and to pin 11 IC4 If pin 11 IC4 does not follow pin 8 IC4 then replace IC4 If pin 23 of IC1 does not go low when the unit is switched on there is a problem with ICI Check that the reset circuit is operational pin 4 IC1 should be a constant DC level between 3V and 5V If not check for open circuit or short circuit and replace faulty component if neccessary Ensure that the crystal inputs are correct A sine wave of the cyrstal frequency should be at pins 2 and 3 if ICI Check that pin 5 is high and pin 7 is low If not check that the pull up and pull down circuits are ok If these signals appear ok
7. the analogue part and the digital part The make up of these separate parts is as follows ANALOGUE DIGITAL UNIT ON OFF CCT MPU BATTERY CHARGER ROM AUDIO I O CCT RAM MODEM DECODER DC DC CONVERTOR LATCH SERIAL I O LED ON OFF CCT Any faults which occur on the logic board can almost always be divided down to being in either one or the other of these two categories EQUIPMENT NEEDED TO CARRY OUT BOARD REPAIR The following is a list of the equipment which is required to be able to track down and repair faults on the logic board Oscilloscope more than 10MHz BW 2 channels divide by 10 probes Ohmeter DVM Circuit Schematic Component layout diagram Component listing Working Keyboard LM Module Power Supply and speaker jig see diagram 4 3 1 It is useful also to have a good working logic board for comparison purposes To examine a suspected faulty logic board first fix it to the good keyboard LCM module and the power supply speaker jig That way there is little possibility of faults in these parts effecting your work Also the extended cable on the power supply speaker jig enables easier access to the PCB for probing etc SYSTEM SELF TEST The system software in the PXI000 contains an in built simple self test routine to assist in checking the operation of the following RAM path to the LCM LED cct audio o p stage which could point to a fault in the digital side e g a s c between audio o p
8. white and ground C with cathode to ground b Connect a latch action switch between wire B red and ground Test the opertion of the serial port as follows i Turn on PX ii Insert the special cable with switch open into socket J3 on PX iii Type text of at least 15 lines into P iv Press PRINT LED should flicker at high speed v Close switch LED should go off vi Open switch LED should flicker again vii LED eventually stops flickering after PLEASE WAIT disappears from the screen 8 AUDIO INPUT OUTPUT SOCKET Construct the following circuit using a cable with a 2 5mm mono plug at one end and the other end open See diagram BN e a Connect PX speaker across open terminals Test socket J4 as follows i Turn on PX Press ON STOP D ii Sound should be heard from PX speaker iii Insert 2 5 mm plug of special cable into socket J4 of PA iv Now there should be sound from the external speaker and none from the speaker in the PX 3 5 mm Stereo plug white A red B A Output B Input power shield C i C Ground Fic gt SA fla E 4 A a i Pra gt e ada Fig 3 5 2 sla 9 SELF TEST FACILITIES INCLUDED IN SOFTWARE The following is a description of facilities that are present on the PX1000 only those with software version V2 or later that will assist unit testing The tests are iniated by pressing the ON STOP key in combination with another key ON STOP Z
9. 3 CS a ce eg ep an Da em Dan Dan Dan Dan So Man GR a 1 2 SPECIFICATIONS General Dimensions Lenght Height Width Weight Operating Temperature Range Humidity Range Storage Temperature Range Technical Power Supply Power Consumption Battery Charge Current Battery Life Memory capaci ty 225 mm 85 mm 29 mm 450 g 10 C to 40 C 0 95 Rh 25 deg C to 55 deg C internal rechargeable 6V battery rechargeable from external 12V DC adaptor lt 150 uA unit off lt 30 mA normal use lt 50 mA transmit receive mode 0 mA high charge 2 MA trickle charge 29 hrs normal use after full recharge 8k 7 4k available to user Mo dem Modulation Standard Frequencies Baud Rates Data Format Parity Header Speaker Output level Receiver Sensitivity Serial Port Voltage Levels Input Output Baud Rate Data Format Parity Audio Socket Voltage Levels Input Output Input impedance Signal Format FSK CCITT V 23 mode 1 600 Bd MARK 1300 Hz SPACE 1700 Hz 300 600 and 1200 selectable from keyboard l start bit 7 data bits LSB first 1 parity bit 2 stop bits Even Transmission starts with 0 5 sec MARK followed by 16 Null Bytes ASCII 00 at the selected baud rate 0 8 sec MARK and 4 Null bytes Set at factory to maximum level allowable by Telephone Authority in country of sale 30dBm MARK 3 to 15V SPACE 3 to 15V MARK 5V
10. 51 187 mm 110 mm 55 mm 500 g internal battery pack rechargeable from external 12V DC adapter Standby 20 mA Printing 400 mA average 1400 mA peak 50 mA 1 hr printing 2 kB 25 characters sec 1200 Bd 1 start bit 7 data bits LSB first 1 check bit 2 stop bits even MARK 3V to 15V SPACE 3V to 15V MARK OV SPACE 11 3V adapter connected 4 3V no adapter connected 59 CHAPTER 2 THEORY OF OPERATION POWER SUPPLY The PXP derives its power from a rechargeable battery pack consisting of six 1 2V cells connected in series giving a nominal voltage of 7 2V at the battery terminals This volatage is applied to the remainder of the circuit via ON OFF switch S1 When the switch is in the ON position two regulator circuits are powered up The first involves IC5 a LM2931Z 5 0V regulator and transistors T6 and T7 The output from this circuit Vb is used to drive the printer motor T6 a TIP32A provides the high current needed by the motor The second regulator circuit involves 106 also a LM2931 This regualator IC provides the 5V Va to power all other IC s Also connected to this IC are transistors T8 and T9 This circuit acts as a battery low voltage indicator to the microprocessor When the difference between the input and output voltage of IC6 becomes less than 0 7V transistor T8 turns off in turn switching transistor T9 which is connected to port DB7 of the MPU This occurs wh
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12. MHz D101632C custom HKWO269 01 010 VERSION F Description microprocessor octal latch EPROM 8K x 8 RAM 1 8 decoder voltage converter quad NAND gate dual voltage sensor modem input amplifier customised hybrid diode diode ceramic cap ceramic cap Ul DI Dil D8 C1 2 9 10 C19 35V dipped tantalum cap C11 12 23 25 10V dipped tantalum cap C3 5 6 7 8 13 16 dipped tantalum cap 1 4 W 1 4 W 1 4 W 1 4 W 1 4 W 1 4 W 1 4 W 1 4 W resistor resistor resistor resistor resistor resistor resistor resistor meter meter pot pot ceramic resonator ceramic resonator 32 way socket 4 pin header reset switch PCB F version 20 21 22 24 C14 R30 R33 R37 R31 32 35 R22 36 R2 Ri R39 R38 PI 2 P3 XT 1 XT2 Jla J5 51 42 besch besch jt jwen ee IND AV CO IND m NI 3 4 HYBRID TYPE TH528 ON LOGIC BOARD F parts deleted parts inserted KEYBOARD A160 3 1405 646 2001 2011 2013 IN4148 4K7 Ohm D101631C HS J0861 01 240 HSJ0838 Type transistor diode resistor capacitor S1 IC8 R37 Description diode LED resistor 32 way plug socket 3 5 mm stereo socket 2 5 mm mono 43 Component No ap an en A en en an en an an TI T9 9 D2 D7 D9 DIO 8 R3 R21 R23 R29 R34 R40 27 C4 15 17 18 4 Comp No
13. Qty per unit Dl D9 9 DIO 1 RI Ri6 16 jl 1 JS J4 44 LOGIC BOARD VERSION H 3 d cd 3 3 _ 3 E 2 3 ind di a di dd A P N Type No Description Comp No Qty per unit 201 HD6 303 microprocessor IC 1 l 252 74HC373 507 octal latch IC 2 l 213 27C64 EPROM IC 3 l 210 HM6264LP 15 8K x 8 RAM IC 4 1 251 74HC138 506 1 8 decoder IC 5 1 321 ICL7660CPA voltage converter IC 6 250 74HCOO 505 quad NAND gate IC 7 1 320 ICL7665CPA dual voltage sensor IC 8 1 280 TCM3101JD 512 modem IC 9 203 TA7330P input amplifier IC10 l TH536 513 customised hybrid UI 1 1405 1N4148 diode DI 1 1450 AA119 diode D14 15 2 1005 27pF ceramic cap C1 2 9 10 4 1020 560pF ceramic cap C19 28 29 3 1105 6 8nF ceramic cap C26 27 2 1301 0 luF 35V dipped tantalum cap Cl1 12 23 3 1312 luF 35V dipped tantalum cap CIA 15 2 1315 4 7uF 10V dipped tantalum cap C3 5 6 7 8 13 16 20 21 22 24 11 615 120 Ohm resistor 1 4 W R33 1 617 180 Ohm resistor 1 4 W R31 32 35 3 626 IK Ohm resistor 1 4 W R30 36 2 630 2K2 Ohm resistor 1 4 W R2 1 638 10K Ohm resistor 1 4 W R1 47 2 650 100K Ohm resistor 1 4 W R48 1 not used resistor R29 910 100K Ohm pot meter P22 925 2508 Ohm pot meter P11 2610 4 000 MHz ceramic resonator XTI l 2611 4 433 MHz ceramic resonator XT2 2002 D101632C 32 way socket Jia l 2003 custom 4 pin header J5 3501 HKW0269 01 010 reset switch Si 1 2 PCB H version l m af di
14. The following is a description of how the PX1000 should be tested after repair work has been carried out to ensure correct operation of the unit The test procedure involves checking the operation of the main functions of the unit First carry out the tests ON STOP Z and ON STOP M as described at fm end of this section Then check the operation of each part of the unit as follows 7 1 LCD se Type in one full row of 8 s Check the contrast of the display Ensure that the viewing angle is correct and that there is no flickering Check the operation of all dots and fixed messages La 2 KEYBOARD be Press CAPS LOCK LOCK should appear in the upper middle part of 1 the display Type in the following 7 ABCDEFGHI JKLMNOPQRSTUVWXYZ 1234567890 Return abcdefghi jkimnopqrstuvwxyz A Make sure the proper character appears on the display for each key pressed Make sure there is a bleep as each character is pressed Press each of the following function keys in turn and make sure of the correct response to each key depressed Press ON STOP to cancel each function each time Key Response on display MARGIN SET RIGHT MARGIN AT 40 PRESS AGAIN CODE EN DECRYPT TEXT 01 PRESS AGAIN CALC CAN NOT CALCULATE CLEAR ALL ERASE ALL TEXT PRESS AGAIN DUMP START RECORD ON TAPE PRESS AGAIN SEARCH SEARCH FOR PRESS AGAIN LEFT SHIFT TEXT displays moves to next text TAB cursor moves to n
15. Ti TI Ti 3 3 Ta MPU When VCC is applied to the MPU by pressing ON STOP as described above the MPU comes out of reset after a delay of 20mS caused by the RC network R3 and C4 The states of ports P20 P21 and P22 immediately after coming out of reset decide in which mode the MPU will operate P21 is tied to ground P20 is low because it is connected to the port of an IC which is powered down and P22 is pulled high via R7 Consequently the MPU operates in the Multiplexed Mode This means that the DATA bus is multiplexed with the lower 8 lines of the ADDRESS bus The MPU inputs NMI and STB are tied to VCC and so are always inactive The ON STOP key is also connected to the external interrupt i p IRQ This input is pulled high by resistor R6 when the ON STOP switch is open Diode D5 prevents battery voltage appearing on this input Diode D2 provides immediate reset of the MPU on power down by rapid discharge of C4 Switch S1 between MPU RST and GND is included to provide the facility to completely reset the system ADDRESS AND DATA BUSSES As mentioned above the data bus and lower address bus are multiplexed So to be able to separate the different signals there is a latch IC2 74HC373 used for the address outputs The ouputs of this latch are always enabled via pin 1 which is tied to ground These outputs are controlled by the address strobe signal AS which is output from pin 39 of the MPU When this signal
16. When pressed is equivalent to a cold start of the unit i e as if the unit is being turned on for the first time The text memory is cleared A copy right message giving the software version number will appear briefly on the display and the unit does a self test routine This routine consists of operational checks on the LCD module the RAM the audio o p and the LED The results of these tests are indicated as follows Three beeps and three LED flashes The unit has attempted to WRITE and READ to every location in the RAM IC4 including those locations needed by the program itself but has found that it is not reading correctly what it has written into some or all locations This could be because of a faulty RAM IC or open cct between the MPU ICI and the RAM or between the decoder IC5 and RAM Two beeps and two LED flashes This indicates that the RAM test has been successful but that there has been an error when checking the LCD This could have been because of a faulty LCD module or open cct between the LCD and the main unit One beep and one LED flash This indicates that the above two tests have been successful A fault in either the LED cct and or the audio o p cct can be detected if either the beeps and or the LED flashes do not operate as described above ON STOP D When pressed the LCD screen is cleared and the modem transmits a continious mark space signal at 1200 Bd without header This signa
17. a voltage of approximately 5V at its output pin 5 using reservoir and pump capacitors C6 and C7 The main RAM IC4 6264 is powered directly from the battery pack via diodes D3 and D4 which ensure the correct supply voltage for this IC MA BATTERY CHARGE CCT The battery charge circuit consists of a dual voltage sensor IC a 7665 108 and a current drive circuit consisting of transistors 13 T11 and T12 and resistors R37 and R42 The operation of the circuit is such that discharged batteries are initially charged at a high rate of 0 3 C where C is the battery capacity which is 170 mAh until they reach a specific voltage of 7 5V at which point the rate is reduced to a trickle rate of less than 0 01C When the charger is inserted 12VDC appears at pin 38 of the hybrid The low level of the battery voltage is detected at Si of IC8 which turns on T3 via output OUTI 13 is actually turned on by pull up R43 as OUTI is now high impedance This in turn turns on transistors 111 and T12 via current limiting resistor R41 111 shorts out resistor R42 so the current flowing into the batteries is equal to 0 7V divided by the value of R37 which is 13 ohms giving a charge current of approximately 50 mA Diode D8 prevents reverse current through this cicruit from the batteries Capacitor C5 provides power supply decoupling After a short while the battery voltage will rise to 7 5 V which when detected by S2 of IC8 will
18. and pin 23 still does not go low then replace ICl Remember when replacing components on the PXP that there are two versions Always check the correct component listing 4 PRINT IS TOO DARK OR TOO FAINT Check the setting of Pl Vary PI until the desired print contrast is acheived If it is not possible to acheive correct contrast at any setting replace T10 If the contrast is still faulty try replacing the print head 4 1 COMPONENT LISTING PXP 40 PRINT MASK VERSION PCB M80C49 172 uPD449C 74HC373 LB1256 LM2931Z 74HC00 6033Y 2SC2001 1153Z 2SA1069 IN4148 30pF 470pF 560pF 10nF 100nF 50V luF 16V 10uF 10V 22uF 10V 22uF 16V 3 3 Ohm 100 Ohm 270 Ohm IK Ohm 2K2 Ohm 3K3 Ohm 3K9 Ohm 4K7 Ohm 10K Ohm 12K Ohm 27K Ohm 47K Ohm 82K Ohm 100K Ohm 180K Ohm 56 Ohm 100K Ohm 22K Ohm 6 MHz SS 12ZA 06P HS J0861 01 240 MTP401 40AN Description microprocessor 2K RAM octal latch dot driver 5 0V regulator quad 2 input NAND NPN transistor NPN transistor PNP transistor PNP transistor diode ceramic ceramic ceramic ceramic ceramic cap cap cap cap cap tant cap tant cap tant cap tant cap NOT INCLUDED resistor resistor resistor resistor resistor resistor resistor resistor resistor resistor resistor resistor resistor resistor resistor resistor resistor 1 8W 1 8W 1 8W 1 8W 1 8W 1 8W 1 8W 1 8W 1 8W 1 8W 1 8W 1 8W 1 8W 1 8W 1 8
19. because of the nature of connector 3 which shorts the terminals when the plug is inserted The BUSY READY state is controlled from the MPU output port P23 This port turns on or off transistor T5 and 111 When they are on T3 is on and T2 is off Therefore the BUSY signal is low active When P23 is brought low T5 and Tll are off T2 is on and the BUSY signal is not active When the printer is off this cicuit presents a high impedence output to the PX1000 The PX1000 has a pull up resistor on its serial input so the high impedance output of the PXP40 will cause it to see a READY state This is neccessary to be able to operate the PX1000 while still connected to the PXP40 which is turned off each time CR is pressed the PX1000 will not hang waiting for a READY signal from the printer When the PX1000 is connected to the PXP40 while the recharge adapter is inserted power to this circuit is provided via diode D6 T2 is biased on via resistors R11 and R26 As long as the PXP is not busy then charge current for the PX1000 is provided via R8 T2 and DIO This circuit is also short cicruit protected with DIO and R3 BUFFER Valid data which appears on the serial input pin of the MPU pin 6 is stored in the RAM IC IC2 which has a capacity of 2kB When printing the MPU fetches the next byte and feeds it to the printer drive circuit The outputs of the IC are pulled down via resistor network RNI This ensures a steady input to Lat
20. by four HD44100 LCD segment column drivers and a HD44780 dot matrix controller The controller IC also contains character generator ROM as well as character generator RAM which gives the user ability to define up to 14 extra characters The contrast of the LCD is fixed The MPU communicates with the LCM via a ten signal connection J2 This connection contains the four upper data lines Do to D7 as well as the following Vcc power supply Vec E GND i li R W R W signal from the MPU which tells the LCD controller whether the MPU wants to WRITE to or READ from the LCM LCDE active high enable signal from the decoder via invertor of IC7 and a blocking diode DI and pull up resistor which convert the high voltage output from IC5 which connected directly to the battery to normal TTL levels Rs o p from the LCM to indicate to the MPU that it is ready recieve data and or commands All data and commands for the L M from the MPU are sent in 4 bit nibbles via the upper four data lines D5 to D7 in a two byte sequence Commands are written to location 8000 which access a write only register while data is written and read at 8001 All data for the operation of the display is saved and updated in the LCD controller IC The MPU only writes data when it wants to update the display contents R2 L a a kod J 3 3 3 3 L tid wad wd oo e 3 3 3 eo a _d A La MODEM The modem IC
21. by the MPU it will set the BUSY READY line low BUSY and test the data received If the data is not valid e g a parity error or unknown character then it is ignored If the data is valid i e a printable character or carriage return then it is stored in the 2k buffer The printer is set READY again and waits for new data When 128 valid characters are received the PXP goes BUSY and starts printing one line After the line is printed it waits to receive another 128 characters This way the printer receives data and prints seemingly at the same time If the RAM buffer is nearly full the printer starts watching for carriage returns and when one is received data input is stopped BUSY READY line is put low and the printer starts printing the contents of the buffer If no carriage return is received the printer will begin printing as soon as the buffer is full When data input stops i e no data is seen at the input for a certain lenght of time the remaining contents of the text in the RAM buffer are printed In order to prevent unwanted empty lines on the print out trailing spaces before a carriage return will be ignored The printer does not use Escape characters Therefore if an escape character is received this character is ignored as is the following character This way text with embeded escape sequences for use with other printers will be printed correctly on the PXP40 When the battery voltage falls below approximate
22. cause T3 to turn off by shorting its base to ground and also 111 and 112 Now the charge current is determined by the voltage accross R37 and R42 in series giving a current of approximately ImA The actual level at which the high rate of charge switches out is determined by potentiometer Pi IC8 also has an output pin OUT2 which gives an indication to the MPU when the batteries are low and need recharging The level at which this output switches is set by the resistor network R12 R13 and R14 a low output indicating low batteries Resistor R5 pulls the output high when the internal switch is off Inbuilt hysterisis in IC8 prevents output oscillation This involves outputs Hl and H2 which change state when the trip point is reached thus via R10 and R11 effectively changing the detection levels The voltage must reach the new level before the output will switch again MPU CLOCK CIRCUIT The heart of the system is the microproccessor which like every other MPU must have a clock source from which to operate The clock circuit for the micro is made up from a 4 0 MHz parallel resonant fundamental crystal AT cut This together with two capacitors Cl and C2 provides a sine wave signal at the MPU pins XTAL and EXTAL of 4MHz in frequency This is divided down internally in the MPU so that the system clock is 1MHz wi 3 3 3 3 i d di 3 2 EE dl 3 ci voi AO sd pod as is 2 79 3 Ta 3 3 3 3 3 3
23. is high the outputs will follow the inputs When the signal goes low the outputs will remain until the signal goes high again The 8 bit data bus is connected to RAM IC4 ROM IC3 and the Keyboard The upper four data bits are connected to the LCD module The address bus is connected to RAM ROM and to the Keyboard The upper two address lines Al4 and Als are connected to the decoder IC5 The system is an 8 bit data 64K memory system DECODER A decoder chip 8 IC5 74HC138 is used to determine which part of the circuit the MPU wishes to address at any one time The memory is divided into four equal parts of which the following locations are used by the program 0000 001F Internal Registers 0020 007F External Memory space 0080 00FF Internal RAM 0100 1FFF Main External RAM 2000 3FFF not used 4000 4001 KEYBOARD 4002 7FFF not used 8000 8001 LCM 8002 DFFF not used E000 FFFF EPROM The inputs to the decoder are Al5 Al4 and the E signal system clock from the MPU Any time the MPU addresses a valid part of the memory map the relevant output will go low Otherwise all the outputs are high EPROM The program memory is contained in 8K EPROM IC3 2764 and is located at address C000 in the system memory It is enabled when the i p s Gl C and B to the decoder are as follows GI C B 1 1 X This combination will bring output Y6 low which is connected to the chip enable i
24. level on this pin Power to the modem is controlled by T6 which is turned on by the MPU output P11 via resistors R26 and R40 only when the modem is in use This reduces overall power consumption of the PX T6 is in turn fed from VCC by a seperate transistor T2 and not by TI because of the rather high current current consumption of the modem circuit Zener diode Z2 of value 5V6 ensures 5V to the modem even though the battery voltage may vary This is neccesary so that i p s CDL and RXB remain constant Capacitor C8 provides power supply decoupling The frequencies used are of the CCITT Standard V23 for a baud rate of 600 Bd regardless of the i p baud rate to the modem The data can be in any of three different speeds 300 600 or 1200 bits s r AUDIO OUTPUT AMPLIFIER Analogue output from the modem IC is fed through a complementary driver buffer stage consisting of Darlington pairs T8 and T9 and resistors R31 and R32 before being fed to the speaker The signal is ac coupled via capacitors C20 and C21 R33 varies the actual voltage across the speaker and so the output volume level Power to the output amplifier is switched with the modem by transistor T7 via resistors R27 and R28 aa Reti eve nina i A a e o CR Ee 12 AUDIO INPUT AMPLIFIER Analogue input picked up on the microphone is fed first to the limiting circuit D9 DIO and R35 then to the filter circuit R34 and E and then to the fir
25. on the displays should be used 4 To enter a command in the message use the lower case letter corresponding to the particular command These letters are listed in table 5 3 2 The position where the commands are entered in relation to the text is the same as that described in the Display operating manual Note that otherwise the actual letters have no direct bearing to the particular command 5 Sixteen spaces must be entered at the end of the message 6 The text must be limited to 2000 characters as this is the maximum memory area of the displays 7 It is not possible to view the message in running mode as it would run on the display 8 No carriage return should be inserted in the message This is because the carriage return will change the display into run mode and all text after the carriage return will be lost After the message has been sent the PX will send a carriage return as it normally does This will set the display to run mode When the mesage is created connect the PX to the display and send at the high speed from the PX 1200 Bd to program The old display series operate at 300 Bd with echo Because of the echo it is not possible to program the old series with the PX The later version series operates at 1200 Bd without echo _ 3 3 d 3 3 3 3 3 3 3 ij A 3 3 dA A A3 3 3 9 ae 73 3 3 3 3 3 3 Togo i 3 3 3 cade CHAPTER 6 ACCESSORIES 6 1 STANDARD The unit is delivered with a Ma
26. should first be examined First press ON STOP NOTE Certain types of faults will cause the circuit to turn itself off immediately after it is turned on This can be a nuiscance when trying to trace signals on a scope To overcome this problem it is a good idea to seperate the power off signal of the MPU from the rest of the circuit e g cut pin 10 ICI But do not forget to make good this connection after the main fault has been repaired With an oscilloscope check each IC for Vcc and GND If they are not present on any IC then there is a power supply problem Check the power lines leading to the relevant IC for short or open circuits Once these are established check the MPU IC1 for the following signals MPU pin no signal description 2 3 XTL Crystal signal i p 4MHz sine wave 6 RESET 2 5 5V 4 NMI 5V 7 STBY 5V 5 IRQ DN 40 E IMHz TTL square wave 39 SCI IMHz 0 3uS SV 0 7uS OV see diagram 4 3 2 If these signals are ok the MPU can be presumed to be in working order If the signals on pins 2 and 3 are not correct check for these signals at the crystal terminals If not present try replacing the crystal If the signals on pins 4 5 and 7 are not present check the connection between these pins and Vcc If the RESET pin 6 is not a constant voltage level between 2 5 and 5 V then there is a fault with the reset circuit on the hybrid and this must be replaced Look now at the keyboad enable pin pin 19 on the MPU I
27. signals from the MPU AO Tp The operation of this test routine is described in section 3 3 PP a a 3 3 di di 8 RN cd d 25 ANALOGUE FAULT REPAIR Faults in the analogue part of the circuit are generally relatively easy to track down by tracing through the relevant circuit For example if there was a fault in the LED drive circuit one would first check to see if the LED worked in either of the two modes in which it normally operates i e when transmitting or receiving or when the adaptor is inserted If it is found that it never works then one would check the LED itself and work back to see where the fault occured In this way the fault which could be an open or short cct or faulty transistor or faulty LED would be quickly traced A similar approach would be used for other faults in this category See accompanying flowcharts on the following pages 79907203d SfVdTU VIVOS 21827 4 IIVIGSY CIS GAN ALTAVA YIVATY 72 FIV 76272 4 07 CUIYGAN ok UY 4 ou Iroz UNO NIINI NNO NIINI LINDY WOXI 13108 Mid 4374407510 TIAL OY VOD 977 TIVIS IS IN NHSOM LON 077 ES E ie HWE LS TL VITA 0 TOONV RACH MIIMA 79 LIAS VIVIFY LL LI Md ALM YS Viva IS ATA I GIUGAN JO JENId NIJAL 78 LIAVS ATA Md ALTAVI YNAT SININ IN UI OdG E NYOM NGAN god AIIN 977 JAVI OL AIGO N LTAVI ALTAV A FILL 00700
28. tabs Bottom part of unit Cover for LCD with transparent screen Speaker Microphone a set of stickers 3 pcs state country LCD screws 9 pes Case screws 6pcs rubber feet 4 pcs insulation sheet 1 pc flexible PCB 1 pc 4 way J5 connector with wires accoustic sealing ring a Soft case b cardboard box amp sleeve c foam d audio amp serial cables e manual state country 12V DC adapter state country id 3 BA d 3 cd A aa d 34 alleg Ty L a f 6 cas Ri LOGIC BOARD F 39 LOGIC Boaeo E COMPONENT LAYOUT lt EC ET E ET E E E E E E EU E E E E E E gt E bA west tec KEYBOARD COMPONENT LAY our PX7000 Bessi ai Zu E IEA EA ER IE gt CD sa CD an ES Raro aaa EEN ed RS ed Ee E A ES ES EL EL E EL E EL EL EL EL EL EL E EL ES ES 7 3 COMPONENT LISTING PX 1000 LOGIC BOARD P N 201 252 213 210 251 321 250 320 280 509 1405 1450 1005 1105 1301 1315 529 535 615 617 626 630 638 541 542 910 925 2610 2611 2002 2003 3501 HD6303 74HC373 507 27C64 HM6264LP 15 74HC138 506 ICL7660CPA T4HCOO 505 ICL7665CPA TOV3101JD 512 M5 1304L TH528 1N4148 1N4001 27pF 6 8nF 0 luF 4 TuF 0 22uF 22 Ohm 120 Ohm 180 Ohm IK Ohm 2K2 Ohm 10K Ohm 22K Ohm 3M Ohm 100K Ohm 200K Ohm 4 000 MHz 4 433
29. the main differences listed below there are a few minor differences also Some circuitry which is in discrete Component form in version F is on the Hybrid on version H The numbering of certain components differs between both versions Because of this unless otherwise stated the component numbers mentioned below refer to the schematic for version F I On the F version IC10 the audio input op amplifier chip is a M51304L Its operaton is similar to 1010 TA7330P on the H version except that its output is limited by an AGC Automatic Gain Control instead of the germanium diodes as used in the H version 2 On version F the CDL level input to the Modem IC9 is set by potentiometer instead of resistor divider as on version H 3 On Version F the voltage sensor IC8 is excluded The battery charge rate is constant at 25mA set by resistors R18 and R37 in series Transistor T3 is always turned on by pull up resistor R16 so RI7 is shorted out 4 The 12VDC supply drives the LED via zener diode from cathode D8 of 6V2 and current limiting resistor 5 There is no resistor from RAM VDD to ground in version F On the H board this resistor ensures that diodes D3 and D4 are full biased making the supply voltage for the RAM closer to specification 6 The RFI reduction circuitry involving capacitors C26 to C29 is not included in the F version I 3 SJ 3 A 03 ca a Ta TEXT TELL PX 1000 BLOCK DIAGRAM
30. 20 SPACE 5V 20 1200 Bd 1 start bit 7 data bits LSB first 1 parity bit 2 stop bits Even V p p max V p p in 120 ohm m O CCITT V 23 600 Bd Standard 3 3 3 3 3 ii ii 3 J ae vrd di di i il le I ad e LI CHAPTER 2 PX1000 THEORY OF OPERATION The following is a detailed technical description of the theory of operation of the PX1000 Version H POWER SUPPLY The PX1000 derives its power from a battery pack containing five rechargeable Ni Cd cells connected in series each with a nominal voltage of 1 2V This generates a nominal voltage of 6V DC at the battery inputs pins 1 and 2 on connector Jo This voltage is applied directly to IC7 which is a QUAD NAND 74HC00 This IC controls the power on off to the remainder of the circuit When the unit is off power is turned on by pressing the key ON STOP This key is connected to the RESET input of a bi stable made up of two NAND gates of IC7 In the off state the output on pin 3 IC7 is low When ON STOP is pressed this output goes high turning on both transistors Tl and T2 via current limiting resistors R8 and R18 Because of zener diode ZI which is 5V7 the voltage on the emitter of 11 is now 5V This is VCC Pull up resistor R7 holds the bi stable in set state The bi stable is reset by a low pulse from MPU port P22 which turns off TI and T2 A voltage convertor IC6 7660 is now powered up and generates
31. 4 RT qui Ree a 7 et 4 va ad w YO 7 er Seen iT i w vi w Su gt H gt v H Ae _ he ai 4 p d KR ile Z A s 75 4 e w ei A idea E a ST e r dos A A Sm i gt _ get Tr Tu de va Fe NaN _ d gt MENTI y 30 Q las me 1 ke po e se A bi E io a Ti 3 3 3 Cd Ti 2 2 1 a 3a a 3 Ta 19 3 E 3 3 SECTION A PX1000 CONTENTS 1 GENERAL INFORMATION 1 1 Product Description 1 2 Specifications THEORY OF OPERATION SERVICE 3 1 Disassembly Assembly 3 2 Calibration 3 3 Test Procedure REPAIR 4 1 Introduction 4 2 Modular 4 3 Logic Board APPLICATIONS 5 1 C MAIL 5 2 Company Message Center 5 3 Connection to Moving Message Displays ACCESSORIES 6 1 Standard 6 2 Optional APPENDICES 7 1 Module Replacement List 7 2 Component Layout Diagrams 7 3 Component Listing 7 4 Schematics SECTION B PXP40 1 2 GENERAL THEORY OF OPERATION SERVICE APPENDICES Page ON 16 16 17 18 22 22 22 24 35 35 36 37 37 37 38 38 39 42 47 50 52 56 60 CHAPTER 1 GENERAL INFORMATION 1 1 PX1000 PRODUCT DESCRIPTION TEXT TELL s PX1000 the Pocket Telex is a pocketable data communications unit for creating and sending receiving text Text can be created using the standard QWERTY keyboard and stored in the unit s memory The memory will
32. 9 TCM 3101 is an IC which basically converts digital signals to analoge signals and vice versa The reason is such that digital information from the MPU can be transformed into a signal which can be transmitted over the telephone network Because of the characteristics of the telephone system the digital signals are converted to audio signals with the two different digital states represented by two different frequencies This system is called Frequency Shift Keying The modem in the PX1000 is used in simplex mode i e it is either transmitting or receiving In transmit mode digital data from the MPU o p Pl4 is fed to the modem Transmit Digital I P on pin 14 The data is internally converted to a sine wave signal on the Transmit Analogue O P pin ll This signal is 1 6V p p and has a frequency of 1700Hz for a 0 i p and 1300 Hz for a 1 i p In receive mode an audio signal appearing on the Receive Analogue I P pin 4 on the modem is converted to a digital signal at Receive Digital o p pin 8 and fed to the MPU i p P20 The audio frequencies are derived from a clock made up from crystal XT2 and capacitors C9 and CIO The voltage level at the Carrier Detect Level i p pin 10 determines what level the modem will detect an analogue signal i p This level is set by the resistor combination R15 and RI6 and decoupler capacitor Cil Potentiometer P2 in combination with C12 adjusts the distortion level of the received data by varying the voltage
33. L 3 3 Ohm resistor 1 8W R8 100 Ohm resistor 1 8W R2 15 2 270 Ohm resistor 1 8W R11 l IK Ohm resistor 1 8W R17 1 2K2 Ohm resistor 1 8W R25 1 3K3 Ohm resistor 1 8W R9 1 3K9 Ohm resistor 1 8W R13 1 4K7 Ohm resistor 1 8W R1 5 10 14 18 23 28 29 8 10K Ohm resistor 1 8W R7 20 2 12K Ohm resistor 1 8W R12 26 2 27K Ohm resistor 1 8W R24 1 47K Ohm resistor 1 8W R6 27 2 82K Ohm resistor 1 8W R22 l 100K Ohm resistor 1 8W R19 21 30 3 180K Ohm resistor 1 8W R3 4 2 56 Ohm resistor 1 4W R16 l 100K Ohm resistor network RN 1 l 22K Ohm pot meter Pi l 11 MHz ceramic resonator CRI l SS 12ZA O6P on off switch Sl 3 5mm stereo plug CON3 l HSJO861 01 240 3 5mm stereo socket CON4 1 MTP40 1 40AN printer mechanism 1 M2 metal bolt 3 M2 metal nut 3 PCB PXP 40 1 6 E E E E E E E E E E E E gt E ET E ki E
34. Remove the printer head and flexi PCB from the mechanism by first removing the retaining clip on the back of the printer head Before doing this the flexi PCB must be separated from this clip by pulling it to the right If glue has been used to keep it in place this can easily be freed Now lift the clip out from the retaining lug at the base of the printer head Hold the paper pressure bar back slightly and with a tweezers or similar small tool slide the printer head up and free from the carriage When it is free from the carriage the head can be brought under the carriage bar and away from the mechanism Replacement is in the reverse order Remove the motor from the printer mechanism by first desoldering the four wires from the printer mechanism PCB Remove the cross head screws that fix the motor to the printer mechanism Replacement is in the reverse order 3 3 3 i 3 A _ 3 3 3 3 3 2 3 od a 3 3 3 Ta a a a tara a Mi 3 57 3 2 TEST PROCEDURE Test the correct operation of the printer using the following procedure Charge the batteries on the PXP by inserting the 12V DC adapter and leaving it in for a minimum of 10 hours The battery pack should now be fully charged and should give 1 hour minimum continuous printing or more than 2 000 lines of 40 characters Check that the battery pack has some charge by turning on the unit The printer head should travel to the end of the line and back ag
35. W 1 4W network pot meter ceramic resonator on off switch 3 5mm stereo plug 3 5mm stereo socket printer mechanism M2 metal M2 metal bolt nut PCB PXP 40 Comp No T1 4 5 9 10 11 T7 T2 3 8 T6 DI DIO C7 8 C6 C20 modification C19 C5 17 C1 2 4 9 10 C3 13 18 C12 14 15 Cli C16 R8 R2 15 R11 R17 R25 R9 R13 R1 5 10 14 18 23 28 29 R7 20 R12 26 R24 R6 27 R22 R19 21 30 R3 4 R16 RNI PI CRI S CON3 CON4 Qty per 60 m Y Y UT NI e K nm DI ka pw EA kw w AV N CO fd ped pwes pe F NO Fe ma a A cd ad A 3 3 a 3 3 61 COMPONENT LISTING PXP 40 NON PRINT MASK VERSION PCB 8037370535 3 3 Type No Description Comp No Qty per unit TMP 80C49AP microprocessor ICI l 6601 TC5516 2K RAM IC2 1 74HC373 octal latch IC3 l LB1256 dot driver IC4 l LM2931Z 5 0V regulator IC5 6 2 74HC00 quad 2 input NAND ICH l BC238B NPN transistor T1 4 5 9 10 11 6 BC338B NPN transistor T7 l BC308B PNP transistor T2 3 8 3 TIP32A PNP transistor T6 l 1N4148 diode Di D7 Dil Dl2 9 IN4001 diode 09 10 2 NOT INCLUDED D8 15pF ceramic cap C7 8 2 470pF ceramic cap C6 l 560pF ceramic cap C20 modification 1 47nF ceramic cap C16 l 100nF 50V ceramic cap C5 16 2 2 1uF 20V tant cap C1 2 4 9 10 5 10uF 10V tant Cap C3 13 18 3 22uF 10V tant cap C12 14 15 3 22uF 16V tant cap C11 1 AND 2 ARE IN PARALLE
36. ain If it does not then turn the unit off and on again If it still does nothing or prints Batteries low please recharge then there is a problem either with the battery pack or with the recharge circuit Create a text in a PX1000 of more than two thousand characters i e more than 50 full lines of text Connect the PX to the PXP to be tested Turn on the PXP Press PRINT on the PX The complete text as in the PX should be printed without error If some of the text is missing or seems overwritten then there is a problem either with the READY BUSY signal or the RAM buffer IC If the text appears either too dark or very faint then the setting of potentiometer PI is incorrect 58 3 3 REPAIR The following is a description of procedure which should help in dealing with any faults that occur with the PXP40 Generally speaking the unit is made to a very high quality standard and should give little operational trouble 1 UNIT IS DEAD First check that the battery pack has not come free from the PCB If it has resolder and attach a piece of foam or sponge to the top of the battery pack so that it is held firmly in place by the housing Check with a voltmeter that the battery pack is fully charged There should be a minimum of 6 3 volts on its terminals If after a 10 hour recharge this is not so check that the charge current is correct by inserting a mili ampmeter between the positive battery terminal and the PCB If t
37. ch IC3 when the RAM IC is disabled 54 PRINTER HEAD DRIVE CIRCUIT The printer drive circuit consists of IC4 and the two circuits involving transistors 11 and 110 IC4 is a dot driver IC LB1256 which drives the seven thermal dots of the printer head directly These dots can be represented by resistors When the MPU wants to send data to the head driver it first reads the ASCII byte stored in RAM Then it calculates from the byte the make up of each 7 bit data block it will send to the driver to make up the 7 x 5 dot character font This block of data is first latched into IC3 then fed through IC4 which acts as a buffer for the print head Because the method of printing is thermal transfer the lenght of time for each dot determines the darkness of the print This is controlled by the circuit around T10 a mono stable whose ouput enables the latch output which in turn feeds the dot driver IC The width of the output pulse from the mono stable is controlled by two factors One is potentiometer PI which varies the time constant of the RC network This is calibrated at the factory to suit the characteristics of the particular print head The input to the circuit comes from the circuit involving Ti This circuit converts the sine wave of the motor tacho feedback signal to TTL level If for any reason the motor speed deviates from the norm e g when the batteries are low or when the paper roll is full then the time spent for each do
38. djusted Place the probe of an oscilloscope on pin 8 of ICl A square wave TTL signal of 1200 Bd should appear on the scope screen Adjust potentiometer P2 such that the mark space ratio of this signal is equal Pot Pl on logic board F is used to set the CDL carrier detect level on the modem IC This pot should be adjusted such that the voltage level appearing on pin 10 of the modem IC9 should be between 0 64 and 0 74 times the voltage VDD at pin 1 of the modem This pot is replaced by a resistor divider network on the H version logic board On logic board H pot PI is used to adjust the level at which the battery charge current rate changes from high to low To fix this first connect a variable voltage supply to connector J5 on the logic board instead of the battery terminals Place a voltmeter accross this supply Place either an oscilloscope or second voltmeter at pin 1 of IC8 Turn on the unit and keep it on by pessing ON STOP D Increase the voltage such that 7 45 V appears on the first meter Set Pl to maximum anti clockwise position Now turn Pi clockwise until the voltage level on the pin 1 IC8 goes low Reduce voltage on the power supply to about 6 5 V and then increase slowly until the voltage at pin 1 IC8 goes low The reading on the first meter should now be between 7 4 V and 7 5 V This pot is not present on the F version logic board as IC8 is not included in the circuit 18 3 3 PX1000 TEST PROCEDURE 1
39. e MPU whether an external device is ready to receive data from the serial output It is designed for use with other RS232C Standard equipment The actual input pin is also used by the 12VDC battery charger Diode Dil prevents current flow into the serial input circuit when the charger is inserted Diodes D6 and D7 limit voltage levels on the MPU to within accecptable limits even when RS232C Standard voltages of up to 15V in magnitude appear at the serial input Resistor R19 is for current limiting and R4 is a pull up to VCC A zero or negative voltage on the serial input pin appears as 0 on P23 of the MPU A 5V or positive voltage on the serial input pin appears as a l on the MPU a E ed 1 8 i A 3 Wd S rd a DA d ad qual qd UA CA ia J PP L so LED DRIVE CIRCUIT The LED is turned by two different methods either directly under control of the MPU and or when the 12VDC battery charger is inserted When being driven by the MPU the circuit involved consists of MPU output P17 transistor T4 resistors R20 R21 and R22 diode D13 and the LED itself A 0 on the MPU output turns on T4 giving a high on its collector which drives the LED on via current limiting resistor R22 A l from the MPU will turn off the LED When the battery charger is inserted the 12VDC drives the LED through the circuit involving T13 D12 R44 R45 and R46 Resistors R44 and R45 provide bias for trans
40. en the battery voltage is approximately 6 2V The battery pack is recharged when the 12V DC adapter is inserted in connector 4 The charge circuit consists of blocking diode 7 and resistor R16 which is 56 Ohms giving a charge current of approximately 50 mA MPU The microproccessor or MPU IC1 80C49 controls the operation of the printer The IC has mask ROM on board which contains the program The MPU derives its clock from crystal CRI which is either 6 MHz or 11 MHz depending on the PCB version The crystal frequency is divided down inside so that the actual system clock is somewhat lower The MPU reset circuit consists of RC network R30 and C4 and diode DI which is connected directly to Va Thus the reset circuit is activated immediately the unit is turned on 53 SERIAL INPUT The serial input for data consists of transistor 14 diode 3 and resistor R7 R9 and RIO T4 and R7 inverts data appearing on the input pin of connector 3 before entering the MPU The circuit will also limit RS232 voltage levels to TTL levels via R9 RIO and D3 SERIAL OUTPUT The serial output circuit consists of transistors T2 T3 T5 and T11 This circuit has four functions First it must be able to provide a BUSY READY signal to the PX1000 when printing Secondly it must give a READY signal to the PX1000 when the printer is off Thirdly it must be able to provide charge current for the PX1000 And lastly it must be short circuit protected
41. ext tab point on display RIGHT SHIFT TEXT displays moves back to previous text INSERT cursor changes to insert cursor DELETE character to the left of cursor is deleted cursor moves left one space gt cursor moves right one space SHIFT D cursor moves to end of current line SHIFT 4 cursor moves to beginning of current line SHIFT Y cursor moves to end of the current text SHIFT A cursor moves to beginning of current text 3 3 a 3 3 3 gt dd 7 3 Ta Ta Ta 3 373 73 OO 19 3 LED Check that LED lights up to the correct brightness in each of the following modes i TRANSMIT Press transmit key on left hand side of unit ii RECIEVE Press RCVE iii 12 VDC connected to socket J3 Ensure that the LED does not flicker when the 12V DC plug is moved in the socket 4 TRANSMIT Check that the unit will transmit acoustically a full message correctly to a good PX at the high transmit speed as follows Enter a message to the PX Press RIGHT SHIFT MARGIN Close lid of PX Place PX onto the good PX with the speakers facing each other Put the good PX into recieve mode by pressing RCVE Press the transmit key on the left hand side of the PX under test When the LED on the test jig PX has stopped flashing the message from the PX under test should appear on the test jig PX with four little square blocks beside a telephone symbol in the top left hand corner of the display Ensure that the LED i
42. he charge current is not correct check the value of R16 If there is no charge current check for open circuits If everything seems ok check that there is no foreign object stuck in the mechanism or that the battery pack is not pressing against the cogs and wheels of the motor drive If there is nothing found then replace the battery pack If the battery pack appears ok then there is a problem with one of the voltage regulator circuits Check that there is 5V at Va and Vb If not check that there is 5V at the output of each regulator IC IC5 and IC6 Replace if faulty If the regulators are ok check the by pass transistors T6 T7 and T8 If the battery pack and charge circuit seem ok but the unit still prints Batteries low please recharge check the circuit around T9 With full batteries pin 19 on the MPU IC1 should be low If this is not the case check for open or short circuits If not found replace T9 8 EE 3 id sd fd 3 3 3 3 3 3 3 3 l 3 3 3 3 3 I 3 59 2 UNIT PRINTS BUT PART OF MESSAGE IS NOT PRINTED Check that the BUSY READY signal from the printer is operational This signal at the connector 3 should be low whenever the printer head is moving and the printer is printing If this is not the case check that BUSY READY control signal on the MPU pin 24 is ok This pin should be high when the pprinter is busy If this output is ok
43. he other three IC s If there appears to be no activity on any of the lower address lines pins 3 to 10 it is possible that the LATCH IC2 is faulty Check that pin 11 IC2 has the same signal as pin 40 ICI If the i p signals on IC2 appear valid but there is no o p seperate one of the o p signals from the remainder of the circuit e g cut the pin If there is now still no valid o p then IC2 is faulty and must be replaced If the board is still faulty then it must be the MPU that is faulty Replace and check again speaker mic bottom housing SA CI 3 3 3 ABA AB 3 3 da 3 3 ii 3 3 A 3 A 3 aj 2356 CHAPTER 5 APPLICATIONS 5 1 C MAIL C MAIL is the name given to an Electronic Mail System developed by West Tec Ltd and which is designed for use by small to med ium sized companies Its purpose is to enable members of the company to be always able to communicate with each other even if in different time zones etc It consists of a central mini computer which can transmit and receive text to and from the PX1000 via the telephone system The computer contains software which enables users of the system to leave messages for other users and also collect messages that have been left for him To set up the system one needs an IBM or compatible PC with a minimum of 64 k memory and minimum of 360 KB disk drive capability Also neccessary is an RS232C Serial Interface board A modem capab
44. hnical problems with the PX1000 and the suspected module Some modules still have some value even if faulty and these should be returned to WEST TEC LTD If there is physical damage to the unit e g scratches or cracks in the housing or stickers or rubber feet are missing these parts can also be replaced A list of the separate modules and their part numbers is given in the Appendices at the end of this manual PROBLEM SYMPTOMS FAULTY MODULE 1 Blank or black display but LCD Module unit appears to function otherwise i e keys click transmit and print ok 2 Unit will work only with mains Battery pack adapter inserted 3 No audio signal when sending Speaker no key click 4 Random characters on display Logic Board no response from keyboard even after reset 5 One or more keys not functioning Keyboard 6 Unit will not recharge and LED Adapter does not burn when adapter inserted and no 12V DC output from adapter SY TAGO FJYNOFTJOY YIVITY 0001 Kd 23 LY VS NTAOY Y IN Ad AN SLY VI A NIN OG A ave yo wo NIR GAY SAIN NK A AV TI S1G LINA IIVISIA LINN LSIL ATGWISSY 7 09A FIVISIS 9yvoe 2907 IIN TTY LY VI INI SAOH MOL 408 JINVNO YOLAIVIV TIVISIY YO0L 4 VOY 0009 LYISNI mi 000 xd 4 7727 94 4 3 PX1000 LOGIC BOARD REPAIR PROCEDURE Basically the PX1000 logic board can be split into two distinct parts
45. hold up to 7 400 characters or 4 to 5 pages of standard A4 The text is viewed on a single line of 40 characters Liquid Crystal Display Inbuilt in the unit is an easy to use yet sohisticated word proccessor Text can be sent and received by telephone using the unit s on board simplex acoustic modem Also text can be transferred to a printer or computer via an RS232C compatible serial port Via this port also text can be received from a computer or other data communications device The unit is powered from an internal rechargeable battery pack which is charged from an external adaptor The unit will operate for more than five hours after a full recharge The memory contents are kept as long as the battery pack is charged There are visual indications on the LCD of the quality of telephone reception the amount of memory used when the battery pack is low as well as other text information There is also an audio input output audio socket which can be used for storage and retrieval of data from a standard tape recorder There are different versions of the PX1000 available The basic unit is the Encrypt version which contains the extra function enabling text to be encrypted according to a key which is selected by the user The original text once encrypted is practically impossible to retrieve without knowledge of the exact key The Calc version has instead of the encrypt function the possibility to do basic arithmetic calculations
46. ins Adaptor for recharging the battery pack a Serial Cable for serial communications an audio cable for use with a tape recorder an operator s manual and soft case 6 2 OPTIONAL PXP40 printer The PXP40 is a portable 40 column printer developed especially for use with the PX1000 This unit is described in detail in the second half of this manual Serial Adapter This is an interface cable which can be used to enable serial communication between the unit and almost any other other computer terminal printer or data epuipment with serial interface This cable comes with a booklet giving the neccessary hardware settings for communication with the most popular makes of equipment Telephone Adapter This is a unit which enables the pocket telex to be directly connected to the telephone line eliminating the environmental noise interference problems associated with accoustical coupling and thus ensuring error free communication Use of this unit is restricted to those countries where in it is approved by the telephone company 7 1 PX1000 MODULE LIST PX 3 PX 4 PX 5 PX 6 PX 7 PX 8 PX 9 PX 10 LOGIC BOARD BATTERY PACK BOTTOM HOUSING LCD COVER AUDIO TRANSDUCER OTHERS PACKAGE ADAPTER 38 DESCRIPTION LCD PCB with LCD glass and driver circuit J ve di e Keyboard PCB with rubber pad keys upper casing LED and flexi cable PCB main circuit Battery pack of five cells with solder
47. istor T13 turning it on which drives the LED on via current limiting resistor R46 Diodes DI2 and DI3 act as blocking diodes to prevent either one of the LED drive circuits from interference with the other Both circuits are capable of operating together when they do the LED burns brighter because of higher current AUDIO TRANSDUCER Audio input and output to and from the unit is via an audio transducer which acts as both microphone and speaker Because the unit operates in simplex mode only this transducer will either be microphone or speaker at any one time AUDIO INPUT OUTPUT SOCKET Audio signals can be input and output to and from the PX directly as well as acoustically via socket J4 When there is something connected in this socket the audio transducer is disconnected from the i o circuitry and signals are fed directly from the external device to these circuits RFI REDUCTION CIRCUITRY Circuitry is included to reduce the amount of Radio Frequency Interference which is associated with the high rate of activity around the MPU and on the address and data lines Two oe of reduction are used One is to actually reduce the amount of noise on the power lines This i j Ce p is is done by the capacitors The second method is to insert filters on the input and output signals These filters are made up from capacitors Cl to C4 in conjunction with chokes LI to L6 14 DIFFERENCES BETWEEN H VERSION AND F VERSION As well as
48. l can be used as the input signal when tuning potentiometer P2 on the logic board of another unit The signal output is stopped by pressing ON STOP ON STOP E When pressed the LCD is cleared and the modem transmits a continious 10 sec mark 10 sec space signal without header This feature can be used to checked the quality of the modem output e g signal amplititude frequency The signal output is stopped by pressing ON STOP ON STOP M When pressed the unit does a WRITE READ test of the text RAM area If this test is successful the message MEMORY OK appears on the display If unsuccessful the message is MEMORY ERROR 29 CHAPTER 4 REPAIR 4 1 INTRODUCTION The PX1000 is a high quality electronic unit which should give little trouble to the user However if there does happen to be a problem with the unit this chapter describes how that problem can be solved The unit can be broken down on a modular basis These separate modules can be purchased from WEST TEC LTD All problems with the unit can be isolated to one of these modules To bring a faulty unit back to working order all is needed is to replace the faulty module Because of the construction of the individual modules little if any repair work can be done on them This does not apply to the logic board and a seperate repair procedure for this is described in section 4 3 4 2 MODULAR REPAIR PROCEDURE The following list indicates some potential tec
49. le of operating at CCITT Standard V 23 mode 1 connects the PC to the telephone line via the RS232C port Optionally a printer with Centronics interface can be connected to get hard copies of messages etc If this is required it is neccessary to have a parallel printer board on the PG Communication with the system involves calling the telephone number and sending a PX message headed by a certain command This command indicates to the system what type of operation you want to carry out After the message has been sent the PX is put into receive and the reply is sent by the system On later models of the PX a special C MAIL function automatically puts the PX into receive mode after sending the message On older models this must be carried out manually Full details of how to set up and operate the system and also the system software are available from West Tec Ltd 5 2 COMPANY MESSAGE CENTER The Company Message Center is a system developed by West Tec Ltd which enables small to medium sized companies to have messages sent from the PX1000 from any location where there is a telephone printed on a printer at a central place e g the company base The system consists of a printer with Centronics type interface which is connected to the telephone line via a CCITT Standard V 23 Mode 1 compatible modem with auto answer capability and the TEXT TELL Message Center interface unit To operate the system the center is called and the me
50. ly 6 2 V the PXP prints the message Batteries low please recharge and further input and printing is blocked until the unit is switched off and the battery pack recharged If the paper roll jams or the printer mechanism is blocked in some way the motor is prevented from burning out by a timing device which will switch the motor off if printing of one line takes too much time 56 lt CHAPTER 3 SERVICE 3 1 DISASSEMBLY ASSEMBLY To disassemble the unit for calibration or repair purposes use the following procedure L 2 Remove the roll of paper by tearing it where it enters the print mechanism Remove the five cross head self tap screws on the bottom side of the unit Turn the unit right side up and lift off the upper housing There may have been adhesive used in the vicinity of the 3 5 mm plug Care should be used when seperating the housings in this case The plastic paper cover can now be seperated from the unit Remove the battery pack froM the PCB by desoldering the terminal solder tags When replacing the battery pack ensure that the insulation paper is in place Remove the printer mechanism from the PCB by first removing the paper advance wheel Desolder the flexible PCB from the component side of the main PCB Desolder the five signal wires on the left hand side from the printer mechanism PCB Remove the three nuts and bolts holding the mechanism to the main PCB Replacement is in reverse order
51. p CE of the EPROM This occurs when anywhere in memory above C000 is addressed Because only 8k Eprom is used C000 to DFFF is redundant When any other place in memory is addressed the EPROM is disabled because CE i p is high and so its data o p s are high impedance 3 a A d ci RAM RAM is located at address 0000 in memory and takes up 8K This includes the RAM internal to the microproccessor which is 128 Bytes as well as the external RAM which is an 8K HN6264 IC4 The external RAM is used mainly for text storage but also is used by the program The program uses up to 600 bytes leaving 7 4K available for text storage There are two chip select i p s to the RAM IC CS1 and CS2 CSI which is active low is used by the decoder to access RAM during normal running In this situation CS2 which is active high must be high In power down mode the contents of the RAM IC must be protected from corruption which could occur while the power to the MPU is decaying and its outputs are unpredictable Power off is controlled by the MPU Before cutting power the MPU first brings o p P13 low which is connected to CS2 Also connected to this pin is a pull down resistor Ri which ensures that the RAM remains disabled until power up again During running mode RAM is enabled when the inputs to the decoder are as follows Gl C B 1 0 0 This situation occurs when the MPU addresses any loaction in memory
52. ross head screws and remove the LCD cover To separate the LCD module from the keyboard PCB desolder the ten contacts of the flexi PCB from the LCM PCB To access the rubber key pad and keys snip the tops off the plastic pillars which hold the keyboard PCB to the unit and lift off the keyboard PCB Replace the PCB by melting down the pillars over the PCB holes Because the pillars get smaller each t ime this cannot be done too often The flexi PCB can be separated from the keyboard PCB by desoldering the ten contacts as with the LOM PCB To remove the flexi PCB from the unit completely it must first be bent over and then slid through the hinge lad 3 A ta LA LA LA L3 13 lana L A its 3 2 CALIBRATION ADJUSTMENTS The only adjustments which need to be done on the PX1000 are to two potentiometers on the logic board These adjustments are done before the unit leaves the factory but may in some cases need to be redone because of slipping of the setting due to vibration etc The two pots to be adjusted are different depending on whether the board is an F or H version To adjust both first remove the bottom housing Pot P2 serves a similar function on both boards Its purpose is to minimise the distortion on the received modem signal To adjust this either directly or accoustical couple another PX to the unit Press ON STOP D on the other unit Press RCVE on the unit to be a
53. s operational while transmitting if 12 VDC is connected to the unit the LED will flicker while transmitting if 12 VDC is not connected the LED will flash on and off while transmitting 5 RECEIVE Test that the PX recieves correctly and completely a full message transmitted acoustically from a good PX at high speed as follows Put the PX into recieve mode by pressing RCVE Place PX onto the good PX with the speakers facing each other Enter a message into the good PX Press RIGHT SHIFT MARGIN on the good PX Press the transmit key on the good PX After the LED on the test jig has stopped flashing the message entered to the good PX should appear in the PX under test A perfect reception is indicated by four squares appearing after the telephone symbol in the top left hand corner of the display Ensure correct operation of LED while recieving its operation is similar to that of the transmit mode Ensure minimal amount of environmental noises during transmit recieve tests 6 PRINT Test the print function of the PX as follows Insert message containing all the different characters available on the PX Connect good PXP40 printer to PX via socket J3 Press PRINT on the PX Make sure the printer prints the message completely as sent from PX SO 7 SERIAL INPUT OUTPUT Construct the following circuit using a cable with a 3 5 mm stereo plug at one end and the other end open see diagram 3 331 a Connect a LED between wire A
54. ssage is sent from the PX in the normal way The interface unit processes the message before sending it to the printer It will also send a reply giving details of the reception quality and the time and date Full details of the operation of the system as well as information on the the interface unit is available from West Tec Ltd 36 5 3 CONNECTION TO MOVING MESSAGE DISPLAYS Although not originally designed for the purpose the PX1000 can be used to program TEXT LITE s Moving Message displays Programming is done serially from the PX1000 serial output port to the display s serial input cable with a connection from the PX output pin to the display s input pin is all that is required To use the PX1000 to program a display first enter the required text into the PX keeping the following points in mind l Any margin can be used when creating the text but a margin of 13 should be used when sending the text to the display This way the first character sent to the unit is a carriage return which is what the display will expect this changes the display from run mode to edit mode 2 The first four characters of the message should be 0 s i e the right shifted zero on the PX This is neccessary to give a delay while the display is echoing the carriage return mentioned in 1 above 3 All characters typed should be upper case as the displays use only upper case and lower case codes are used for commands Also only characters used
55. st of two amplifier stages via ac coupler 17 The first is a transistor invertor type with gain of 100 set by resistors R38 and R39 The output is ac coupled by C25 The second consists of an audio op amp 1010 TA7330 with gain of 100 determined by feedback circuit of R30 R48 C16 and C19 The output from the op amp is ac coupled by C14 then limited by two germanium diodes Dl4 and D15 and resistor R47 and ac coupled again by C23 This ensures a maximum i p signal to the modem of 0 7v p p which is specified for this IC Because the modem is only concerned with the frequency of the signal possible clipping caused by these diodes will not effect performance IC10 is power supply decoupled by capacitor C13 and Clo SERIAL OUTPUT CIRCUIT The serial output circuit consists of transistor T5 and resistors R23 R24 and R25 Serial data is fed from output P24 of the MPU to the base of PNP transistor T5 via R24 such that a on P24 turns on T5 and a l turns it off The emitter of T5 is connected to SV and the collector to 5V via resistor R25 Serial output is taken from the collector of T5 via current limiting resistor R26 The effect of the output circuit is such that a 1 on P24 MPU gives 5V at the output while a 0 gives 5V These levels are compatible with the RS232C Standard SERIAL INPUT CIRCUIT The serial input circuit consists of P23 of the MPU R4 R11 D6 D7 and Dil It is used to indicate to the th
56. t should be a TTL level signal with a low level pulse of 0 4 msec every 65 ms see diagram 4 3 3 If this signal is present it is more than likely that IC s 1 2 3 4 5 are ok and there is a fault with the interface to the LCD module LCM Another indication that the program is working and that these IC s are ok is if there is a beep everytime a key is pressed and the unit turns itself off after 50 sec 35 Check that there is no fault with the 32 pin connector Jl Using a circuit schematic trace and check that the same signals for the LCM on the logic board are present at the pins of J2 connector on the keyboard PCB If not there is probably a faulty connection at Ji i e dry or open solder joint The operation of the decoder IC5 should now be checked The following features are characteristic of a working decoder a Signal on pin 40 of IC1 should also appear on pin 6 of IC5 If not check for open circuit b No two o p s pins 7 9 10 11 12 13 14 15 should be low at the same t ime O p s YI Y3 Y5 Y7 pins 14 12 10 7 should never be low d No o p should be low when E signal pin 6 is low e When C i p pin 3 is high YO and Y2 pins 15 and 13 will never be low Note It is useful to use signal on pin 40 ICI as oscilloscope trigger while making these observations If these conditions are met we can assume that the decoder is ok If not try replacing the decoder Now wi
57. t will be decreased so that the print contrast is constant The mono stable also provides a safety feature for the printer in that if the motor stops for any reason e g paper gets stuck the monostable will time out thus disabling the latch outputs and consequently disabling the dot driver output The TTL converted signal from the tacho of the motor is fed also to the MPU pin 1 so that it can monitor the position of the motor PRINTER MOTOR INTERFACE The printer drive motor is a DC motor driven from the 5V supply Vb which is connected directly to the positive termina of the motor M The motor is turned on and off under control of the MPU via port P21 on ICI This output controls whether Vb or GND appears at the motor negative terminal M The motor TG signal from the motor is a sine wave tacho signal and its use is described above The home signal is the output from a micro switch which momentarily shorts to GND each time the motor reaches the left most position This gives the MPU an indication of the position of the motor after power on d wa Aa 3 3 3 3 i 3 e d d di 8 3 vo jn 55 SOFTWARE The control software for the printer operates as follows On power on the MPU comes out of reset and after approximately one second is ready to receive data The BUSY READY line is held high to indicate printer READY When a bit stream is received
58. th an oscilloscope check the signals on the pins of the RAM IC4 bearing in mind the following a These signals are connected to the MPU IC1 the ROM IC3 and the LATCH IC2 b The DATA and lower ADDRESS BUSES are multiplexed Firstly the signals on pins 26 27 IC4 should be the same as those on pins 16 38 ICl respectively If not check for open circuit Also signal on pin 26 IC4 should be high Looking at the other pins what will be seen will be difficult to analise but after a while a definite pattern will be identified What should be looked for here are two or more signals which either appear the exact same or which contain definite voltage levels not including transitions which are not TTL If found then the pins with these signals should be examined with an ohmeter for short circuits sacd id edi Lo 3 3 A 3 A Y B 3 AB 3 ed ld d vesi Id Id d 3 73 Ta gt 3 03 a TA a 3 294 If a short circuit is found the shorted tracks should be followed where they lie next to each other and closely examined It might be that a stray blob of solder got lodged on the PCB It is also possible that there may be a short on an IC If an IC is suspected try replacing it Also look for pins which do not appear to have any signal on them i e open circuited If such a signal looks suspect it can be quickly compared with the corresponding signal on either of t
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