OHAUS MB25 Service Manual
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OHAUS MB25 Service Manual

Moisture analyzer
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SERVICE MANUAL
Ohaus Corporation 7 Campus Drive, Suite 310, Parsippany, NJ 07054 USA (973) 377-9000

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Summary of Contents for OHAUS MB25

  • Page 1 SERVICE MANUAL Ohaus Corporation 7 Campus Drive, Suite 310, Parsippany, NJ 07054 USA (973) 377-9000...
  • Page 3 SERVICE MANUAL 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.

  • Page 5: Table Of Contents

    3.8.1 Testing the Heater Circuit .................3-8 3.8.2 Removing the Heater on the MB23 ..............3-9 3.8.3 Removing the Heater on the MB25 ..............3-10 3.8.4 Replacing the Heater on the MB25 ..............3-10 3.8.5 Replacing the Heater on the MB23 ..............3-11 3.8.6 Testing the Thermal Overload Device .............
  • Page 6 4.4.1 Precision Test ....................4-2 4.4.2 Repeatability Test .....................4-3 4.4.3 Linearity Test ....................4-4 CHAPTER 5 DRAWINGS AND PARTS LISTS MB23 and MB25: Housing & Internal Parts ..............5-2 Appendix A STANDARD CALIBRATION Weight Calibration ....................A-1 Temperature Calibration..................A-2 Service Calibration ....................A-3 Appendix B SOFTWARE SERVICE TOOL Software service tool location ..................
  • Page 7 Clear plastic In-use Cover .................. 3-16 3-41 Housing Chamber ....................3-16 3-42 MB25 with top open ................... 3-16 Segment Display ....................4-1 MB23 & MB25: Housing & Internal Parts .............5-2 Temperature Calibration Kit installed ..............A-1 Ohaus Corporation www.ohaus.com MB23 and MB25 Service Manual...
  • Page 8 TABLE OF CONTENTS MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

  • Page 9: Chapter 1 Getting Started

    INTRODUCTION This service manual contains the information needed to perform routine maintenance and service on the MB23 and MB25 Moisture Analyzers. Familiarity with the Instruction Manual is assumed. The contents of this manual are contained in five chapters: Chapter 1 Getting Started – Contains information on service facilities, tools, specifications, and the mechanical and electronic functions of the product.

  • Page 10: Tools And Test Equipment Required

    2. Standard electronics tool kit 3. Soldering iron (50 watt) and solder (rosin core solder, not acid core). 4. Solder remover 5. Ohaus Temperature Calibration Kit P/N 11113857 6. 50g calibration weight 7. Strain Gage Simulator (optional) 8. Soft, lint-free cleaning cloth 9.

  • Page 11: Specifications

    CHAPTER 1 GETTING STARTED SPECIFICATIONS Complete specifications for the Ohaus MB23 and MB25 Moisture Analyzers are listed in Table 1-1. When a scale has been serviced, it must meet these specifications. TABLE 1-1. SPECIFICATIONS Model MB25 MB23 Capacity 110g 0.2% (3g sample) 0.3% (3g sample)

  • Page 12: Analyzer Operation

    CHAPTER 1 GETTING STARTED ANALYZER OPERATION This section contains information on the basic operation of the scale. 1.5.1 Overview of the Controls Figure 1-1. MB23 and MB25 Function Labels. TABLE 1-2. FUNCTIONS OF DISPLAY CONTROLS Button: Name: Functions: Button: Name:...

  • Page 13: Operating Modes

    (Short press) Enters Edit mode for the time setting. The value will blink. (Short press while time setting blinks) Toggles between AUTO and time value. Accepts the blinking setting. If AUTO is selected: Weigh mode is entered. MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...
  • Page 14 At the end of the test (Run Mode), the display blinks the test result. Changes the unit of displayed result: weight (grams) > % Moisture > % Solids. Exits to Weigh mode. Sends current displayed value to the RS232. Ohaus Corporation www.ohaus.com MB23 and MB25 Service Manual...

  • Page 15: Power

    20 minutes after turning the unit on, for the electronics to stabilize. When the scale is first turned on, the factory default is to weigh (in grams) and tare items without setting the menus. MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

  • Page 16: Communications Interface

    CHAPTER 1 GETTING STARTED Communications Interface The MB23 and MB25 are equipped with a bi-directional RS232 interface, accessed through a DB9-pin connector on the rear of the unit. Following are available parameters (defaults in bold): 1. Baud Rate: 1200; 2400; 4800; 9600; 19,200 2.

  • Page 17: Chapter 2 Troubleshooting

    A Load Cell that is even slightly bent or corroded should be replaced. – Check the heating unit for corrosion or other damage. If a problem arises that is not covered in this manual, contact your local Ohaus office. MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

  • Page 18: Error Codes

    Replace Main PCB. Section 3.6. Err 10.7 Temperature out of control (Current temperature is Use a Power Supply Regulator 20° C higher than target setting) Replace temperature Sensor Section 3.8.9. Replace main PCB. Section 3.6. Ohaus Corporation www.ohaus.com MB23 and MB25 Service Manual...

  • Page 19: Problem Solver

    Dirt or debris in unit. Clean the unit thoroughly. Cooling air current blocked. Clean the ventilation grill. Defective Load Cell. Replace Load Cell. Section 3.7. Defective Main PCB. Replace Main PCB. Section 3.6. MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

  • Page 20: Chapter 3 Maintenance Procedures

    4. Make a visual inspection for faulty connectors, wiring, and loose hardware. OPENING THE MB23 AND MB25 Common hand tools are sufficient to disassemble the MB23 and MB25 moisture analyzers. Turn the Analyzer off and unplug the power cord before you begin.

  • Page 21: Mb25 With Top Open

    CHAPTER 3 MAINTENANCE PROCEDURES OPENING THE MB23 AND MB25 (continued) 1. Lift the top. Handler 2. Remove the Pan Handler, Pan Support and Cleanout Tray. (See Figure 3-1.) Support 3. Pull away the Housing Chamber: Cleanout Tray Pull Figure 3-1. MB25 with top open.
  • Page 22 CHAPTER 3 MAINTENANCE PROCEDURES OPENING THE MB23 AND MB25 (continued) 7. Gently lift the Top Housing so the rear stays in place and the front rises. (See Figure 3-6.) Figure 3-6. Lifting the Housing. 8. Remove the three cables connected to the Power PCB.

  • Page 23: Preliminary Checks Of The Top Housing Components

    MB23). It is also possible at this stage to test the Power PCB and Main PCB. Figure 3-8. Cables for Temperature Sensor, Fan, Ground, and Heater, disconnected. (Note: MB23 shown; MB25 does not require ground cable for heating element.) 3.3.1 Test the Heater Circuit 1.

  • Page 24: Testing The Power Pcb

    Power PCB to the bottom housing. 6. Install the replacement PCB, insert Figure 3-10. Power PCB. the screws removed previously. 7. Resassemble and calibrate. (See Appendix A.) Perform all tests. (See Chapter 4.) MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

  • Page 25: Replacing The Main Pc Board

    Figure 3-13. Display LCD on Main PCB. 5. Install new backlight LCD. Position backlight cables like originals, and solder in place. 6. Soldier in the LCD leads. Ohaus Corporation www.ohaus.com MB23 and MB25 Service Manual...

  • Page 26: Replacing The Load Cell

    10. Install the Load Cell, using the Software Service Tool. (See Appendix B.) 11. Calibrate the Moisture Analyzer (See Appendix A.) and Perform all Figure 3-15. Load Cell with ribbon cable tests. (See Chapter 4.) attached at bottom. MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

  • Page 27: Repairing And/Or Replacing The Heating Unit Parts

    Heater’s leads. Resistance should be approximately 45 ohms for the MB23, and approx. 5.7 ohms for the MB25. 2. Move the cables while checking to test for an intermittent cable problem. Read- ings should not fluctuate during this test.

  • Page 28: Removing The Heater On The Mb23

    4. Grasp the Heater’s base and lift it up and out. (See Figure 3-22.) This will release the Heater from the retainer clips opposite. Retainer clips Figure 3-22. Lifting out the Heater. MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

  • Page 29: Removing The Heater On The Mb25

    CHAPTER 3 MAINTENANCE PROCEDURES 3.8.3 Removing the Heater on the MB25 1. Remove the screws and washers that secure the Reflector, and lift it off. (See Figure 3-19.) 2. Remove screw and washer anchoring the cable. (See Figure 3-23.) Figure 3-23. Screw and washer anchoring Heater Cables.

  • Page 30: Replacing The Heater On The Mb23

    4. If test fails, replace the device. 5. Reassemble the Heating Unit. 6. Perform a Temperature Calibration. (See Appendix A.) 7. Conduct Performance Tests. Figure 3-26. Reset button on the Thermal (See Chapter 4.) Overload Device. MB23 and MB25 Service Manual 3-11 Ohaus Corporation www.ohaus.com...

  • Page 31: Replacing The Thermal Overload Device

    (See Figure 3-27.) 4. Fit the washer and then the nut, and use a wrench to tighten the nut. Figure 3-27. MB25 Thermal Overload Device. 5. MB23: Mount the ground cable ring. (See Figure 3-28.) Then use a wrench to tighten the nut.

  • Page 32: Replacing The Fan

    Frame Housing, first on one side, then on the other, to release it from the Top Housing. 9. Install the replacement Fan by following these steps in reverse. Figure 3-33. Removing the Fan. MB23 and MB25 Service Manual 3-13 Ohaus Corporation www.ohaus.com...

  • Page 33: Replacing The Temperature Sensor

    Top Housing. 12. Perform a Temperature Calibration. Figure 3-36. Removing screws and (See Appendix A.) washers securing Temperature Sensor. 13. If Calibration is successful, conduct Performance Tests. (See Chapter 4.) Ohaus Corporation www.ohaus.com 3-14 MB23 and MB25 Service Manual...

  • Page 34: Installing The Top Housing

    6. Place the small plug over the front screw after tightening it, as shown. Figure 3-38. Placing Plug on Top Housing. 7. If the Protective Glass on the MB25 was removed or replaced, install it as follows: 8. Place the Protective Glass in the groove in the Heater Frame Housing in front of the Heater.

  • Page 35: Clear Plastic In-Use Cover

    Figure 3-40. Clear plastic In-use Cover. Figure 3-41. Housing Chamber. 12. Install the Pan Handler, Pan Support Handler and Cleanout Tray. (See Figure 3-42.) Support Cleanout Tray Figure 3-42. MB25 with top open. Ohaus Corporation www.ohaus.com 3-16 MB23 and MB25 Service Manual...

  • Page 36: Chapter 4 Final Testing

    CHAPTER 4 FINAL TESTING FINAL TESTING Before servicing the MB23 or MB25 Moisture Analyzer, an operational test and various performance tests should be done to determine if the unit meets specifications. Turn the Moisture Analyzer on and allow it warm up for at least one hour before performing these tests.

  • Page 37: Precision Test

    Inspect and correct if necessary. (See Off-Center Load Test.) 3. Foreign material or debris between the pan and the base will cause the Analyzer to fail the test. 4. Vibrations, drafts or a non-level surface can cause failures. Ohaus Corporation www.ohaus.com MB23 and MB25 Service Manual...

  • Page 38: Repeatability Test

    6. Mean = (Reading 1 + Reading 2 + Reading 3 + Reading 4 + Reading 5 7. + Reading 6 + Reading 7+ Reading 8 + Reading 9 + Reading 10) / 10 Mean =________ MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

  • Page 39: Linearity Test

    8. The difference in the weights of the test mass should be within the Linearity tolerance in Table 1-1. If not, calibrate (see Appendix A.1) and repeat the test. 9. If the unit remains out of tolerance, the Load Cell may need to be replaced. Ohaus Corporation www.ohaus.com MB23 and MB25 Service Manual...
  • Page 40 CHAPTER 5 PARTS LISTS & DIAGRAMS This section of the manual contains exploded views for the MB23 and MB25 Moisture Analyzers. The exploded view drawings are designed to identify the parts which can be serviced on the Analyzer in the field.

  • Page 41: Mb23 And Mb25: Housing & Internal Parts

    CHAPTER 5 PARTS LISTS & DIAGRAMS MB23 & MB25: HOUSING & INTERNAL PARTS MB23 & MB25 Figure 5-1. MB23 & MB25: Housing & Internal Parts. Ohaus Corporation www.ohaus.com MB23 and MB25 Service Manual...

  • Page 42: Mb23 & Mb25: Housing & Internal Parts

    CHAPTER 5 PARTS LISTS & DIAGRAMS MB23 & MB25: HOUSING & INTERNAL PARTS TABLE 5-1. MB23 & MB25: HOUSING & INTERNAL PARTS Drawing Item Description Top Housing Chamber Reflector Heater, MB23 Heater, MB25 Temperature Sensor Heater Frame Housing Thermal Overload Device (MB23)
  • Page 43 CHAPTER 5 PARTS LISTS & DIAGRAMS Ohaus Corporation www.ohaus.com MB23 and MB25 Service Manual...

  • Page 44: Weight Calibration

    Remove any load from the Pan, including the sample pan. Note: To cancel calibration without saving changes, press: (Place weight on pan.) 50.000 (Clear pan.) ---- --0-- -done- Analyzer returns to Weigh mode. MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

  • Page 45: Appendix A Standard Calibration

    Use a Temperature Calibration Kit. (Available as an accessory.) If the analyzer has been recently used, allow at least 30 minutes before performing calibration. Use only the OHAUS Temperature Calibration Kit. Using other methods could damage the Analyzer. (Remove pan and pan support.) (Appears in software prior to 1.07.)

  • Page 46: Service Calibration

    (Place weight on pan.) 100.00 lINea (Clear pan.) ---- (Place weight on pan.) (Place weight on pan.) 50.00 100.00 (Place weight on pan.) (Clear pan.) 50.00 (Place weight on pan.) (Clear pan.) 100.00 done MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...
  • Page 47 APPENDIX A STANDARD CALIBRATION Ohaus Corporation www.ohaus.com MB23 and MB25 Service Manual...

  • Page 48: Appendix B Software Service Tool

    3. Open the folder ‘Service Software’. 4. Open sub folder ‘Service’. 5. Open sub folder ‘Service Tools’. 6. Download tool and database file. 7. Open sub folder ‘Service Manual’. 8. Download service tool instruction manual MB23 and MB25 Service Manual Ohaus Corporation www.ohaus.com...

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