TABLE OF CONTENTS
Ohaus Corporation www.ohaus.com
i
MB23 and MB25 Service Manual
CHAPTER 1 GETTING STARTED
Page No.
1.1
Introduction ..............................................................................................................1-1
1.2
Service Facilities ......................................................................................................1-1
1.3
Tools and Test Equipment Required ........................................................................1-2
1.4
Specifications ...........................................................................................................1-3
1.5
Analyzer Operation ..................................................................................................1-4
1.5.1 Overview of the Controls ...................................................................................1-4
1.5.2 Overview of the Display Indicators ....................................................................1-4
1.5.3 Operating Modes ..............................................................................................1-5
1.5.4 Power ...............................................................................................................1-7
1.5.5 Power On & Off .................................................................................................1-7
1.6
Communications Interface ........................................................................................1-8
CHAPTER 2 TROUBLESHOOTING
2.1
Troubleshooting .......................................................................................................2-1
2.1.1 General Procedures for Troubleshooting ..........................................................2-1
2.2
Error Codes..............................................................................................................2-2
2.3
Problem Solver ........................................................................................................2-4
CHAPTER 3 MAINTENANCE PROCEDURES
3.1
Preventive Maintenance ...........................................................................................3-1
3.1.1 Preventive Maintenance Checklist ....................................................................3-1
3.2
Opening the MB23 and MB25 ..................................................................................3-1
3.3
Preliminary Checks of the Top Housing Components ..............................................3-4
3.3.1 Test the Heater Circuit ......................................................................................3-4
3.3.2 Test the Temperature Sensor and Cable ..........................................................3-4
3.3.3 Test the Fan ......................................................................................................3-4
3.3.4 Test the Ground Circuit on the MB23 ................................................................3-4
3.4
Testing the Power PCB ............................................................................................3-5
3.5
Replacing the Power PCB ........................................................................................3-5
3.6
Replacing the Main PC Board ..................................................................................3-6
3.6.1 Replacing the Display LCD ...............................................................................3-6
3.7
Replacing the Load Cell ...........................................................................................3-7
3.8
Repairing and/or Replacing the Heating Unit Parts ..................................................3-8
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 ............................................................. 3-11
3.8.7 Replacing the Thermal Overload Device ......................................................... 3-12
3.8.8 Replacing the Fan ........................................................................................... 3-13
3.8.9 Replacing the Temperature Sensor................................................................. 3-14
3.9
Installing the Top Housing ...................................................................................... 3-15
CHAPTER 4 FINAL TESTING
Page No.
4.1.
Final Testing ............................................................................................................4-1
4.2
Operational Test ......................................................................................................4-1
4.3
Segment Display Test ..............................................................................................4-1
4.4
Performance Tests ...................................................................................................4-1
