SECTION 4
MAINTENANCE
Type 422 AC-DC
Change information, if any, affecting this section will be found at the rear of this manual.
Introduction
This section of the manual contains maintenance inform
ation for use in preventive maintenance, corrective mainten
ance or troubleshooting of the Type 422.
Cabinet Removal
The cabinet can be removed from the indicator as
follows:
1. First remove the power supply from the rear of the
indicator as follows:
a. Loosen the four securing screws located in the rear
feet of the power supply.
b. Separate the two units by sliding the power supply
to the rear off the support rods.
2. Remove the three screws located in the trim casting
which hold the cabinet to the rear of the indicator.
3. Slide the cabinet to the rear and off the support rods.
Power-Supply Cover Removal
The cover can be removed from the power supply as
follows:
1. First remove the power supply from the indicator as
given in step 1 above.
2. Remove the screw located directly below the fuse
holder and remove the battery box and battery pack from
the power supply.
3. Remove the four screws located in the trim casting
and the three screws located on the bottom (see Fig. 4-1).
4. Slip the power-supply cover off the power-supply
chassis.
WARNING
Dangerous potentials exist at several points through
out this instrument. When this instrument is operated
with the covers removed, do not touch exposed con
nections or components. Some transistors may have
elevated cases. Disconnect power before cleaning the
instrument or replacing parts.
Fig. 4-1. Location of cover mounting screws on rear and bottom of
AC-DC Power Supply.
PREVENTIVE MAINTENANCE
General
Preventive maintenance consists of cleaning, visual
inspection, lubrication etc. Preventive maintenance per
formed on a regular basis may prevent instrument break
down and will improve the reliability of this instrument.
The severity of the environment to which the Type 422 is
subjected determines the frequency of maintenance. A
convenient time to perform preventive maintenance is
preceding recalibration of the instrument.
Cleaning
General. The Type 422 should be cleaned as often as
operating conditions require. Accumulation of dirt in the
instrument can cause overheating and component break
down. Dirt on components acts as an insulating blanket and
prevents efficient heat dissipation. It also provides an elec
trical conduction path which may result in instrument
failure.
The cabinet provides protection against dust in the
interior of the instrument. Operation without the cabinet in
place necessitates more frequent cleaning. The front cover
EB
4-1
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