Chapter 5 Preventive Maintenance
5-2
CAUTION:
Some internal components can be damaged by small amounts of static
electricity. A properly grounded antistatic wrist strap must be worn while handling
any internal component. For more information about appropriate safety precautions,
see Chapter 7, “Servicing.”
1. Turn off power and disconnect power line.
2. Remove the field mirror (see Figure 7-2) by removing the four Allen head screws
holding it to the main bench (use a 9/64 Allen wrench). Remove the relay mirror, by
removing the three Allen head screws holding it to the main bench (use a 9/64 Allen
wrench).
3. Carefully clean each mirror using a cotton swab and methanol. Rinse with distilled
or deionized water. Dry by blowing clean dry air over the mirror.
4. Reassemble following the above procedure in reverse. It is not necessary to realign
any mirror following cleaning.
5. Re-install the instrument cover.
6. Calibrate following the procedure of Chapter 4, “Calibration.”
IR SOURCE REPLACEMENT
The IR source control system has been designed to operate the wire wound resistor IR
source conservatively in order to increase its life. Nevertheless, the IR source does have
a finite life. Since the IR source is relatively inexpensive and easily replaced, it is
recommended that the IR source be replaced after one year of continuous use. This
prevents loss of data due to IR source failure. If an IR source is to be replaced on an “as
needed” basis, it should be replaced when:
There is no light output.
After cleaning the optics, the IR light intensities remain below 100,000 Hz.
Since the Model 48C is a ratio instrument, and since replacing the IR source does not
affect the calibration, it is not necessary to recalibrate the Model 48C after replacing the
IR source.
SYSTEM LEAKS AND PUMP CHECK OUT
There are two major types of leaks: external leaks and leaks across the optional zero/span
solenoid valve seals.
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