CHAPTER 3 MAINTENANCE PROCEDURES
MB23 and MB25 Service Manual
3-11
Ohaus Corporation www.ohaus.com
3.8.5 Replacing the Heater on the MB23
1. Grasp the new Heater by its base
and gently press it into the retainer
clips opposite. (See Figure 3-25.)
Insert the base into the slots.
2. Connect the Heater cables.
3. Install the Reflector.
4. Replace the Chamber Top on the
Heater Frame Housing.
5. Insert the four screws that secure
Chamber Top to the Heater Frame
Housing.
Figure 3-25. MB23: Installing the Heater.
6. Repeat Heater Circuit Tests. (See Section 3.3.1.)
7. If tests are OK, reassemble the Top Housing. (See Section 3.8.)
8. Perform a Temperature Calibration. (See Appendix A.)
3.8.6 Testing the Thermal Overload Device
1. Remove the Chamber Top (Section 3.9.1, Steps 1 and 2)
and the Reflector (Section 3.9.2, Step 1.)
2. Perform a continuity test on the
Thermal Overload Device: with
power to the unit off, use an ohm
meter to measure resistance
between the device’s poles.
Resistance should be
zero Ω. If so,
the device is good. If not, proceed to
Step 3.
3. Press the
device’s reset button.
(See Figure 3-26.) Then re-test.
4. If test fails, replace the device.
5. Reassemble the Heating Unit.
6. Perform a Temperature Calibration.
(See Appendix A.)
7. Conduct Performance Tests.
(See Chapter 4.)
Figure 3-26. Reset button on the Thermal
Overload Device.
