OHAUS MB25, Руководство по обслуживанию

Страница: 27 / 48

CHAPTER 3 MAINTENANCE PROCEDURES
Ohaus Corporation www.ohaus.com 3-8 MB23 and MB25 Service Manual
3.8 REPAIRING AND/OR REPLACING THE HEATING UNIT PARTS
1. Remove the four screws that secure the
Chamber Top to the Heater Frame
Housing. (See Figure 3-16.)
2. Use a flathead screwdriver to gently pry
the Chamber Top from the Heater
Frame Housing. (See Figure 3-17.)
Figure 3-16. Screws holding Chamber Top
to the Heater Frame Housing.
Figure 3-17. Separating the Chamber Top
from the Heater Frame Housing.
3.8.1 Testing the Heater Circuit
1. Perform a Resistance Test:
With power to the unit off, use an ohm
meter to measure resistance between
the 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.
3. If OK, test Thermal Overload Device.
(See Section 3.9.4.)
4. If Thermal Overload Device is OK, check
fuses on Power PCB.
5. If fuses are OK, replace Power PCB.
Figure 3-18
. Testing Heater leads’
resistance.
Four
screws to
remove