A & A Scales PT300 Manuel utilisateur
IPT300
Service Manual
A & A Scales
1-813-994-3190
Fax 509-355-3498
www.stainlessscales.com
PT300, Service Manual
Rev B, October, 2000
1
SAFETY SUMMARY
The following general safety precautions must be observed during all phases of
operation, service, and repair of this scale. Failure to comply with these precautions or
with specific warnings elsewhere in this manual violates safety standards of design,
manufacture, and intended use of the scale. Intercomp assumes no liability for the
customer's failure to comply with these requirements.
DO NOT OPERATE IN AN EXPLOSIVE ATMOSPHERE.
Do not operate the scale in the presence of flammable gases or fumes. Operation of
any electrical instrument in such an environment constitutes a definite safety hazard.
DO NOT SUBSTITUTE PARTS OR MODIFY SCALE.
Because of the danger of introducing hazards, do not substitute parts or perform any
unauthorized modifications of the scale.
NOTICE
All rights reserved. The information contained in this publication is derived in part from proprietary and
patent data of the Intercomp corporation. This information has been prepared for the express purpose of
assisting operating maintenance personnel in the efficient use of the instrument described herein.
Publication of this information does not convey any rights to use or reproduce it or to use it for any
purpose other then in connection with the installation, operation, and maintenance of the equipment
described herein. While every precaution has been taken in the preparation of this manual, Intercomp
Corporation assumes no responsibility for damages resulting from the use of the information contained
herein. All instructions and diagrams have been checked for accuracy and ease of application; however,
success and safety in working with tools depend largely upon the individual accuracy, skill, and caution.
For this reason Intercomp Company is not able to guarantee the result of any procedure contained
herein. Nor can they assume responsibility for any damage to property or injury to persons occasioned
from the procedures. Persons engaging the procedures do so entirely at their own risk.
COMPLIANCE WITH FCC RULES
Please note that this equipment generates, uses, and can radiate radio frequency energy. If this
equipment is not installed and used in accordance with the support manual, you are warned that it may
cause interference to radio communications. This unit has been tested and has been found to comply
with the limits for a Class A computing device pursuant to subpart J of part 15 of FCC Rules. These
rules are designed to provide reasonable protection against interference when equipment is operated in a
commercial environment. However, if this unit is operated in a residential area, it is likely to cause
interference and under these circumstances the user will be required to take whatever measures are
necessary to eliminate the interference at his own expense.
PT300, Service Manual
Rev B, October, 2000
2
Table of Contents
SCOPE OF MANUAL......................................................................................................................................... 5
SPECIFICATIONS.............................................................................................................................................. 6
ELECTRICAL....................................................................................................................................................... 6
SERIAL INTERFACE SPECIFICATIONS:.................................................................................................................... 6
PHYSICAL .......................................................................................................................................................... 6
ENVIRONMENTAL............................................................................................................................................... 7
CALIBRATION:.................................................................................................................................................... 7
THEORY OF OPERATION............................................................................................................................... 9
POWER SUPPLY:.................................................................................................................................................. 9
Input protection:........................................................................................................................................... 9
Charger:......................................................................................................................................................10
Switch:.........................................................................................................................................................10
Low Voltage Sensor:....................................................................................................................................11
Regulator: ...................................................................................................................................................11
ANALOG SECTION:............................................................................................................................................12
Instrumentation Amplifier:...........................................................................................................................12
Analog/Digital Converter:...........................................................................................................................12
Microprocessor section: ..............................................................................................................................14
CPU:....................................................................................................................................................................... 14
Memory: ................................................................................................................................................................. 14
Device Selector:...................................................................................................................................................... 14
Switches & Reader:................................................................................................................................................. 14
Display Driver: ....................................................................................................................................................... 15
Serial IN/OUT: ....................................................................................................................................................... 15
TROUBLESHOOTING .....................................................................................................................................16
SYMPTOMS........................................................................................................................................................16
No power up, nothing on display..................................................................................................................16
Power up to random display. .......................................................................................................................16
Power up to test pattern...............................................................................................................................16
Scale shuts off..............................................................................................................................................17
"Locks up."..................................................................................................................................................17
No backlight................................................................................................................................................17
No response to one or more keys..................................................................................................................17
"Bad" weights..............................................................................................................................................17
Jumpy/drifty weights....................................................................................................................................17
Slow operation.............................................................................................................................................17
Low batt indicator won't turn off..................................................................................................................18
Batteries won't charge. ................................................................................................................................18
No totalizing................................................................................................................................................18
ERROR MESSAGES..............................................................................................................................................18
TESTS, WAVEFORMS AND ..................................................................................................................................19
VOLTAGE MEASUREMENTS.................................................................................................................................19
Blank EPROM test.......................................................................................................................................19
SYSTEM CHECKOUT PROCEDURE.........................................................................................................................22
Charger voltage: .........................................................................................................................................22
On / Off switch: ...........................................................................................................................................22
Power Supplies:...........................................................................................................................................22
Amplifier:....................................................................................................................................................23
A/D converter:.............................................................................................................................................23
Lamp:..........................................................................................................................................................23
Keys:...........................................................................................................................................................23
PT300, Service Manual
Rev B, October, 2000
3
Low batt indicator:......................................................................................................................................23
Power down shutoff: ....................................................................................................................................23
SIO (totalizing):...........................................................................................................................................24
Load Cells:..................................................................................................................................................26
PROCEDURES...................................................................................................................................................27
LOADING PADS & BLOCKS..................................................................................................................................27
CALIBRATE SPAN...............................................................................................................................................27
Calibration..................................................................................................................................................27
REMOVE AND REPLACE MAIN CIRCUIT BOARD......................................................................................................29
Disassembly.................................................................................................................................................29
Assembly .....................................................................................................................................................29
REMOVE AND REPLACE LOAD CELL .....................................................................................................................30
Disassembly.................................................................................................................................................30
Assembly .....................................................................................................................................................31
CHECK FRONT/BACK LOAD CELL BALANCE..........................................................................................................31
UNPACKING AND INSTALLATION ........................................................................................................................34
USE OF A LOAD CELL SIMULATOR........................................................................................................................34
COMPLETE LIST OF REQUIRED TOOLS AND MATERIALS .........................................................................................34
Spare parts list ............................................................................................................................................34
Connector pinouts .......................................................................................................................................36
TRANSMIT DATA FORMAT..................................................................................................................................36
PT300 MAIN CIRCUIT BOARD............................................................................................................................37
PARTS LIST .......................................................................................................................................................37
PT300 SUMMING CIRCUIT BOARD PARTS LIST.......................................................................................39
APPENDIX A......................................................................................................................................................40
APPENDIX B......................................................................................................................................................44
SCHEMATICS.....................................................................................................................................................44
TOTALIZING CABLE ...........................................................................................................................................47
CHARGING CABLE.............................................................................................................................................48
INTERNAL CABLE ASSEMBLY.............................................................................................................................50
PARTS.................................................................................................................................................................51
HOW TO REACH INTERCOMP SERVICE ...................................................................................................52
PT300, Service Manual
Rev B, October, 2000
4
Table of Illustrations
FIGURE 1 BLOCK DIAGRAM.................................................................................................8
FIGURE 2 BATTERY CHARGER............................................................................................9
FIGURE 3 SWITCH............................................................................................................10
FIGURE 4 INTEGRATOR/COMPARITOR................................................................................12
FIGURE 5 CONVERSION CYCLE.........................................................................................13
FIGURE 6 LCD DRIVE......................................................................................................15
FIGURE 7 BLANK EEPROM TEST WAVEFORMS ................................................................20
FIGURE 8 BLANK EEPROM TEST, ADDRESS LINES...........................................................21
FIGURE 9 TEST WAVEFORMS ...........................................................................................22
FIGURE 10 SIO MASTER TEST.........................................................................................24
FIGURE 11 SIO SLAVE TEST............................................................................................25
FIGURE 12 LOAD CELL SCHEMATIC...................................................................................26
FIGURE 13 LOAD CELL PLACEMENT..................................................................................32
FIGURE 14 SUMMING BOARD............................................................................................40
PT300, Service Manual
Rev B, October, 2000
5
Scope of manual
This service manual describes the Intercomp PT300 scale specifications, theory of
operation, interconnection, calibration, and servicing. Please refer to the users manual
for detailed operating procedures and application information.
This manual is separated into several sections, each containing information on a
different aspect of the scale. The specifications show the design parameters for the
scale. The theory section includes a circuit description and theory of operation that
explains how the scale works. The service section provides information for
troubleshooting a defective circuit. The calibration section explains how to set the
scale adjustments. The interconnection section shows the way two or more scales
work together to form a larger system. The assembly instructions show correct
assembly and disassembly techniques.
This manual is not designed to be a substitute for proper training in the installation,
operation, maintenance or service of PT300 electronic scale. It is to be used as a
guide for training service personnel or as a reference source for training previously
received.
Caution
Your PT300 scale is covered by a one year warranty and should be referred to the
factory for maintenance within the warranty period. Attempts to make any extensive
repairs within the warranty period may invalidate the warranty. If repairs are needed
after the warranty period, only qualified technicians should attempt such repairs. An
understanding of the principles of operation of the PT300 circuitry as described herein
in necessary for rapid troubleshooting and repair of any scale malfunction.
PT300, Service Manual
Rev B, October, 2000
6
Specifications
Electrical
Display settling
time: 950 milliseconds to typical reading (static).
Accuracy: ±1% of applied load
±1 display division in static mode
±2% of applied load
±1 display division in roll-over mode.
Overcapacity: 105% of nominal capacity.
Safe Overload: 150% of capacity.
Batteries: 6 x 1.2 volt AA nickel cadmium cells.
(Alkaline batteries can be used, but do not attempt to recharge
them).
Battery Life: Approximately 5 years. (1500 charge/discharge cycles).
Battery Duration: Approximately 8 hours of continuous use before the low battery
indicator comes on, and 2 hours after that before the scale
shuts itself off.
Automatic Shutoff: The scale turns itself off when the battery voltage gets down to
approximately 6.3 volts.
Charging Voltage: 11.5 volts - 14.5 volts DC. Protection is provided for accidental
reversal of the charging connections.
Charging Current: Starts at approximately 300 mA and drops down to 50 mA after
8 hours.
Charging Time: 8 hours if the batteries are discharged to the point of turning off
the scale.
Low Batt.: Indicator comes on when the battery voltage gets down to
approximately 7.2 volts.
Fuse: Buss type AGC-1.
Serial interface specifications:
Interface: 1200 baud, 8 data, no parity, 2 stop bits.
Format: Each print line contains
Physical
Overall Dimensions: 3 x 16 x 20 inches / 76 x 406 x 508 mm.
Platform Dimensions: 12 x 12 inches / 305 x 305 mm.
Scale Weight: 37 lb / 16.8 kg.
Display Height: 0.55” / 14mm
PT300, Service Manual
Rev B, October, 2000
7
All metal case provides EMI/RFI immunity.
Caution The scale and connecting cables should be operated at a minimum distance of
3 feet (1 meter) from any transmitting apparatus and least 10 feet (3.3 meters) from a
radiating antenna.
Environmental
Operating Temperature: -20 to 150º F (-28 to 65º C).
Humidity 10 to 95% Non-Condensing.
Calibration:
All scales are calibrated at the factory, a fine span adjustment can be made using the
potentiometer on the PT300 circuit board.
This scale can be used while it is charging.
Caution
Operation outside the range of -20°F to 150°F (-28°C to 65°C) may result in inaccurate
weight values. Storage or operation outside the range of -40°F to 170°F (-40°C to
75°C) may result in a shift in calibration or damage to the scale.
PT300, Service Manual
Rev B, October, 2000
8
Figure 1Block Diagram
Power Supply Battery
Drivers
Low Battery Sensor
On Off
Lamp
Lb/Kg
Zero
Hold/Rel
Total/Local
Print
Switches
Input
Buffer Micro
Controller
Display
Serial
Output
12v
Serial
Input
Receiver
Loadcells
Summing
Board
Analog/Digital
Input
Input
Connector
Output
Connector
PT300, Service Manual
Rev B, October, 2000
9
Theory of Operation
For the following discussion, please refer to the schematics in appendix B.
Power supply:
The power supply section provides a source of ±5 volts, a nickel-cadmium battery
charger, and the detector for low battery condition. The input is designed to accept any
voltage between 10.5 and 14.6 volts.
Q5
D4
D5
D20
Constant
Current
Source
Current
Limiting
Resistor
Charge
Sensor
Battery
Switch
Scale
Gnd
Gnd
Gnd
Gnd
10.0v
9.3v
8.6v
R20
+14.6v-+10.5v
Figure 2Battery Charger
Input protection:
Diode D1 and fuse F1 provide protection from incorrectly connected power or a
circuit fault.
Table des matières
