OHAUS SCOUT Service Manual
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OHAUS SCOUT Service Manual

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Ohaus Corporation
29 Hanover Road
Florham Park, NJ
07932-0900
TM
ELECTRONIC BALANCES
SERVICE MANUAL

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  • Page 1 Ohaus Corporation 29 Hanover Road Florham Park, NJ 07932-0900 ELECTRONIC BALANCES SERVICE MANUAL...
  • Page 2 07932-0900 The information contained in this manual is believed to be accurate at the time of publication, but Ohaus Corporation assumes no liability arising from the use or misuse of this material. Reproduction of this material is strictly prohibited. Material in this manual is subject to change.

  • Page 3: Table Of Contents

    TABLE OF CONTENTS CHAPTER 1 INTRODUCTION Page No. 1.1 Introduction ..................... 1-1 1.2 Service Facilities ..................1-1 1.3 Tools and Test Equipment Required ............1-2 1.3.1 Special Tools and Test Equipment List .......... 1-2 1.3.2 Standard Tools and Test Equipment List ........1-2 1.4 Test Masses Required ................
  • Page 4 TABLE OF CONTENTS (Cont.) CHAPTER 4 MAINTENANCE PROCEDURES (Cont.) Page No. 4.2.3 Performance Tests ................. 4-6 4.2.3.1 Precision Test ................4-6 4.2.3.2 Off-Center Load Test..............4-7 4.2.3.3 Centered Load Test..............4-7 4.2.4 Down Stop Adjustment ..............4-8 4.3 Replacement of Major Components ............4-9 4.3.1 Disassembly .................
  • Page 5 LIST OF TABLES TABLE NO. TITLE Page No. Mass Values ..................1-2 Specifications ..................1-3 Diagnostic Guide ................3-2 Error Codes ..................3-4 Calibration Masses ................4-3 Types of Performance Tests ............. 4-6 Replacement Parts List ..............5-6 LIST OF ILLUSTRATIONS FIGURE NO.

  • Page 7: Chapter 1 Introduction

    1.1 INTRODUCTION This service manual contains the information needed to perform routine maintenance and service on the Ohaus Scout Electronic Balances, 200g, 400g and 600g capacities. The contents of this manual is contained in five chapters and are listed as follows: Chapter 1 Introduction - Contains information regarding service facilities, tools and test equipment, measuring masses, and specifications.

  • Page 8: Tools And Test Equipment Required

    5. Solder (rosin core). 1.4 TEST MASSES REQUIRED The masses required to test the Scout Electronic Balances must meet or exceed the requirements of ASTM Class 4 Tolerance. The mass values are listed in Table 1-1. TABLE 1-1. MASS VALUES...

  • Page 9: Specifications

    CHAPTER 1 INTRODUCTION 1.5 SPECIFICATIONS Complete specifications for the Scout Electronic Balances are listed in Table 1-2. When a balance has been serviced, it must meet the specifications listed in the table. Before servicing the balance, determine what specifications are not met.
  • Page 10 CHAPTER 1 INTRODUCTION...

  • Page 11: Chapter 2 Theory Of Operation

    CHAPTER 2 THEORY OF OPERATION 2.1 BALANCE OPERATION This chapter contains basic theory of operation of the balance. An exploded view drawing is included in Chapter 5 which identifies all mechanical components of the balance. 2.1.1 Operation The AC Power Adapter cord plugs into a receptacle at the rear of the balance. The Rezero On switch when pressed (located on the PC Board), applies power to the balance.

  • Page 12: Transducer Operation

    Figure 5-2, for mechanical components, refer to Figures 2-2 and 5-1. Two types of Transducers are used in the Scout balances, one type utilizes four Strain Gauges in a full bridge configuration, the second type contains two Strain Gauges in a half bridge configuration.

  • Page 13: Printed Circuit Board Circuit Description

    CHAPTER 2 THEORY OF OPERATION PRINTED CIRCUIT BOARD DESCRIPTION ( See Block Diagram Figure 2-3 and Schematic Diagram, Figure 5-2) 2.3.1 Power Supply Power is supplied to the unit from either an AC Adapter which provides 9 volts dc or an internal 9 volt Alkaline battery.

  • Page 14: Low Voltage Detector

    CHAPTER 2 THEORY OF OPERATION 2.3.3 Low Voltage Detector The purpose of the Low Voltage Detector circuitry is to inform an operator when the battery voltage drops to level which would cause improper operation of the balance and require replacement of the battery. Transistors Q4 and Q7 form the low voltage detector.

  • Page 15: Half Bridge Emulator

    CHAPTER 2 THEORY OF OPERATION 2.3.5 Full Bridge Weight A/D Converter (Cont.) Instead of comparing the sawtooth against a reference signal, this circuit compares it against a ramp signal generated by transistor Q2, resistors R2, R3 and capacitor C12. At time zero, capacitor C12 starts to charge through resistors R2 and R3. The output of the ramp circuit starts high and goes low.

  • Page 16: Block Diagram

    CHAPTER 2 THEORY OF OPERATION TEMPERATURE A/D CONVERTER TEMPERTURE INTEGRATOR COMPARATOR SENSOR ELECTRONIC SWITCH U4A, U4F MICROPROCESSOR EEPROM FULL BRIDGE WEIGHT A/D CONVERTER FULL INTEGRATOR COMPARATOR BRIDGE LOADCELL DISPLAY DRIVER ELECTRONIC RAMP SWITCH U4B,U4C, U4D, U4E 10MHz CLOCK HALF BRIDGE EMULATION RESISTOR NETWORK HALF...

  • Page 17: Chapter 3 Troubleshooting

    The repeatability test will quickly point out whether the Transducer (8) is operating properly or whether the problem is due to an electronic malfunction. If a problem arises that is not covered in this manual, contact Ohaus Corporation for further information.

  • Page 18: Diagnostic Guide

    CHAPTER 3 TROUBLESHOOTING TABLE 3-1. DIAGNOSTIC GUIDE REMEDY SYMPTOM PROBABLE CAUSE 1. Check AC Adapter. No display. 1. No power. 2. Replace Power Jack. 2. Power Jack defective. 3. Replace. 3. Weak battery. 4. Clean or replace. 4. Battery connector - poor contact.
  • Page 19 CHAPTER 3 TROUBLESHOOTING TABLE 3-1. DIAGNOSTIC GUIDE (Cont.) SYMPTOM PROBABLE CAUSE REMEDY Displays underweight 4. Down Stop improperly 4. Set per specifications. (Cont.). set. Exceeds off center limit. 1. Defective Transducer. 1. Replace Transducer. Inaccurate readings. 1. Improper calibration 1. Perform calibration pro- (Span or Linearity).

  • Page 20: Error Codes

    CHAPTER 3 TROUBLESHOOTING 3.3 ERROR CODES Scout balances are equipped with software which will display an error condition when it occurs. Table 3-2 Error Codes, describes the various error codes which can appear on the display and specifies the probable reason and remedy.

  • Page 21: Chapter 4 Maintenance Procedures

    CHAPTER 4 MAINTENANCE PROCEDURES 4.1 PREVENTIVE MAINTENANCE Ohaus Scout balances are precision instruments and should be handled as follows: • Store in a clean dry area which is dust free. Use a cover if possible. • Keep clean at all times.

  • Page 22: Testing

    CHAPTER 4 MAINTENANCE PROCEDURES 4.1.1 Preventive Maintenance Checklist (Cont.) 3. Clean the outside of the balance using a damp cloth with water. CAUTION DO NOT USE CHEMICAL CLEANERS OR SOLVENTS OF ANY TYPE. SOME CLEAN- ERS ARE ABRASIVE AND MAY AFFECT THE FINISH OF THE BALANCE.

  • Page 23: Calibration

    Span Calibration. A 300 g calibration mass is supplied with the 600g balance. Linearity calibration requires an additional 100g mass for 200g Balances, 200g mass for 400g balances and 300g mass for 600g balances. Masses are available from Ohaus as accessories.
  • Page 24 CHAPTER 4 MAINTENANCE PROCEDURES 4.2.2.2 Calibration Procedure (Cont.) Span and Linearity Scout balances are calibrated before shipment, however, calibration can be affected by changes in location, temperature, or rough handling. The balance should be warmed up for at least 5 minutes.
  • Page 25 CHAPTER 4 MAINTENANCE PROCEDURES 4.2.2.2 Calibration Procedure (Cont.) Activating Units and Parts Counting Activating Units and Parts Counting Activating Units and Parts Counting Activating Units and Parts Counting Activating Units and Parts Counting 1. When the balance displays , press Rezero On to display the grams indicator "g"...

  • Page 26: Performance Tests

    CHAPTER 4 MAINTENANCE PROCEDURES 4.2.3 Performance Tests Accurate performance of a Scout balance is determined by a series of three perfor- mance tests. The displayed readings are compared with the tolerances listed in Table 4-2. Tolerance values are expressed in counts. A one count change is equal to the last digit shown on the balance display.

  • Page 27: Off-Center Load Test

    CHAPTER 4 MAINTENANCE PROCEDURES 4.2.3.1 Precision Test (Cont.) Adjustment If the deviation for any set of readings (using the same mass placed on the center of the Pan) is greater than +1 count, the balance does not meet the Precision Test specification.

  • Page 28: Down Stop Adjustment

    CHAPTER 4 MAINTENANCE PROCEDURES 4.2.3.3 Centered Load Test (Cont.) Test 1. Place a mass equal to the maximum capacity of the balance on the center of the Pan (6) and note the reading. 2. If the displayed weight is greater than 1 count higher or lower than the value of the applied mass, proceed to paragraph 4.2.2.2 and calibrate the balance.

  • Page 29: Replacement Of Major Components

    Instruction Manual, contact: Ohaus Corporation 29 Hanover Road Florham Park, NJ 07932 USA Tel: 973-377-9000 Fax: 973-593-0359 In the United States call Ohaus Aftermarket, toll free, 800-526-0659 between 8:00 a.m. and 4:00 p.m. EST.

  • Page 30: Disassembly

    CHAPTER 4 MAINTENANCE PROCEDURES 4.3.1 Disassembly This section of the manual contains detailed disassembly procedures of the balance. Refer to Figure 5-1. Before disassembling the balance, it should be noted that components inside of the balance are delicate and need to be handled with care. It is imperative that the Transducer (8) should never be subjected to any excessive torque, stress, or abraison as damage may result.

  • Page 31: Printed Circuit Board (Pcb) (4) And Power Board

    CHAPTER 4 MAINTENANCE PROCEDURES 4.3.1 Disassembly (Cont.) COVER SCREW PLATFORM RETAINING SCREW DOWN STOP ADJUSTMENT TRANSDUCER Mode Mode Re Zero Re Zero Figure 4-8. Cover Removal. Figure 4-7. Platform Removal. 7. With the balance facing towards you, remove the Cover (2) and position the Cover (2) in front of POWER BD CLIPS...

  • Page 32: Replacement

    CHAPTER 4 MAINTENANCE PROCEDURES 4.3.1.1 Printed Circuit Board (4) and Power Board Replacement In an effort to keep service costs down, it is suggested that if the Printed Circuit Board (4) is suspected of being faulty, it should be replaced rather than repaired. To replace the Printed Circuit Board (4) and Power Board, proceed as follows: 1.

  • Page 33: Transducer (8) Replacement - 200 Gram Models

    CHAPTER 4 MAINTENANCE PROCEDURES 4.3.1.2 LCD Display (12) Replacement (Cont.) Refer to the parts list in section 5 for the kit number which contains both parts. To replace the LCD, proceed as follows: 1. Disassemble the balance in accordance with the procedures in paragraph 4.3.1.
  • Page 34 CHAPTER 4 MAINTENANCE PROCEDURES 4.3.1.3 Transducer (8) Replacement - 200 Gram Models (Cont.) 1. Disassemble the balance in accordance with the procedures in paragraph 4.3.1. 2. Turn the balance over and loosen evenly the two Allen head captive Machine Screws (22) (until free) which secure the Transducer (8). 3.

  • Page 35: 4Transducer (8) Replacement - 400 And 600 Gram Models

    CHAPTER 4 MAINTENANCE PROCEDURES 4.3.1.3 Transducer (8) Replacement - 200 Gram Models (Cont.) 10. Assemble the balance by placing the Cover (2) on top of the Base (1) and securing with the Cover screw (26) and Platform (5) using Screw (22). 11.Adjust the Up/Down Stop in accordance with paragraph 4.2.4.
  • Page 36 CHAPTER 4 MAINTENANCE PROCEDURES 4.3.1.4 Transducer (8) Replacement- - 400 and 600 Gram Models (Cont.) 9. Turn the balance over again. While facing the Printed Circuit Board (4), insert the flexible cable from the Transducer (8) into the connector provided for it, on the Printed Circuit Board (4).

  • Page 37: Chapter 5 Drawings And Parts Lists

    CHAPTER 5 DRAWINGS AND PARTS LISTS 5.1 DRAWINGS This section of the manual contains an exploded view and schematic diagram for Scout balances, 200g, 400g and 600g. The exploded view drawing is designed to identify the parts which can be serviced on the balance in the field.
  • Page 38 CHAPTER 5 DRAWINGS AND PARTS LISTS...
  • Page 39 CHAPTER 5 DRAWINGS AND PARTS LISTS Figure 5-1. Exploded View of Balance. 5-3/5-4...
  • Page 40 CHAPTER 5 DRAWINGS AND PARTS LISTS Figure 5-2. PC Board, Schematic Diagram. 5-5/5-6...

  • Page 41: Parts Lists

    CHAPTER 5 DRAWINGS AND PARTS LISTS 5.2 PARTS LISTS This section of the manual contains the replaceable parts for the Scout Electronic Balances, 200g, 400g and 600g. TABLE 5-1. REPLACEMENT PARTS LIST KEY NO. PART NO. DESCRIPTION 300002-010 Base 300001-010...
  • Page 42 5. Items 9 and 10 shown on Figure 5-1 are assembled as part of the Transducers. 6. Ohaus replacement parts warranty only applies to parts purchased from Ohaus Corporation. 7. Transducer kits are supplied with Upstop and Downstop screws.
  • Page 43 SCOUT ELECTRONIC BALANCES P/N 300040-010 R1198...
  • Page 44 Ohaus Corporation 29 Hanover Road Florham Park NJ 07932-0900 SERVICE TRANSDUCER Removal and Replacement Instructions Electronic Balances UTION: UTION: DELICA DELICA TE COMPONENT TE COMPONENT CA UTION: UTION: UTION: DELICA DELICA DELICA TE COMPONENT TE COMPONENT TE COMPONENT DO NO...
  • Page 45 Introduction Introduction Introduction Introduction Introduction The Service Transducer Kit for the 200 gram model contains a transducer and an EEPROM. CAUTION: CAUTION: The service transducer is a delicate component. Use extreme caution CAUTION: CAUTION: CAUTION: when handling it. Do not subject the transducer to abrupt shock or bend the flex cable.
  • Page 46 Turn the balance over and loosen evenly until free the two Allen head captive mounting screws which secure the transducer (see Figure 3). POWER BD CLIPS BOTTOM OF UNIT MOUNTING PLATE BATTERY COMPARTMENT TRANSDUCER UP STOP TRANSDUCER EEPROM CAPTIVE MOUNTING SCREWS PC BOARD Figure 3 Figure 3...
  • Page 47 Refer to the Instruction Manual and calibrate the balance after installation. Ohaus Corporation 29 Hanover Road, Florham Park, NJ 07932, USA Tel: (973) 377-9000, Fax: (973) 593-0359 With offices worldwide. P/N 300035-011 © Ohaus Corporation 1997, 1999 all rights reserved.
  • Page 48 Ohaus Corporation Model:..............ALL Service Training Description:....... PC Board Replacement C305/C505 Transfer solder link settings E12, E13 Portable Plus Transfer solder link settings S1, S2, S3 Transfer solder link settings E3-E9 Transfer R2 (S.A.T.) temperature compensation resistor Portable Advanced CT Transfer solder link settings S1-S4...
  • Page 49 Ohaus Corporation Model:..............ALL Service Training Description:....... PC Board Replacement Explorer / Voyager Analytical and Precision Toploader Transfer IC EEPROM (U5) Transfer IC Transducer ID (U10). Looks like a transistor Transfer U11 EPROM / Microprocessor Explorer / Voyager High Capacity Main PCB...
  • Page 50 Ohaus Corporation Model:..............ALL Service Training Description:....Straingage OCL Adjustment Straingage Transducer OCL Adjustment 1. Place the test weight in the center of the platform. 2. Tare the balance. 3. Move the weight to point A and record the reading. 4. Move the weight to point B and record the reading.
  • Page 51 Ohaus Corporation Model:.............Scout Service Training Description:........Common Faults Error 1 Check the downstop screw Deadload out of range - Perform a linearity cal. If this fails replace the transducer Error 4 Check the downstop screw Wrong cal weight used - Perform a linearity cal. If this fails replace the transducer No Display Check operation of ON switch.

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