Maintenance—Type 422 AC-DC
checking transistor operation are given under Trouble
shooting.
Recalibration
To assure accurate measurements, check the calibration
of this instrument after each 1000 hours of operation or
every six months if used infrequently. In addition, replace
ment of components may necessitate recalibration of the
affected circuits. Complete calibration instructions are
given in the Calibration section.
The calibration procedure can also be helpful in local
izing certain troubles in the instrument. In some cases,
minor troubles may be revealed and/or corrected by recali
bration.
TROUBLESHOOTING
Introduction
The following information is provided to facilitate
troubleshooting of the Type 422. Information contained in
other sections should be used along with the following
information to aid in locating the defective component. An
understanding of the circuit operation is very helpful in
locating troubles. See the Circuit Description section for
complete information.
Troubleshooting Aids
Diagrams. Complete circuit diagrams are given on fold-
out pages in the Diagrams section. The component number
and electrical value of each component in this instrument
are shown on the diagrams. Each main circuit is assigned a
series of component numbers. Table 4-1 lists the main
circuits in the Type 422 and the series of component
numbers assigned to each. Important voltages and wave
forms are also shown on the digrams. The portions of the
circuit mounted on circuit boards are enclosed with a blue
line.
TABLE 4-1
Component Numbers
Component numbers
on diagrams
Diagram
number
Circuit
1-99
1
Channel 1 Input Amplifier
100-199
2
Channel 2 Input Amplifier
200-299
4
Vertical Switching and
Output Amplifier
300-399
5
Sweep Trigger
400-499 6 Sweep Generator
500-599
8
horizontal Amplifier
700-799
9
Calibrator and Regulators
800-899
10
CRT Circuit
1000-1099
11 AC-DC Power Selector
1100-1299 12
DC-DC Regulator
Switch Wafer Identification. Switch wafers shown on
the diagrams are coded to indicate the position of the wafer
in the complete switch assembly. The numbered portion of
the code refers to the wafer number counting from the
front, or mounting end of the switch, toward the rear. The
letters F and R indicate whether the front or rear of the
wafer performs the particular switching function. For
example, a wafer designated 2R indicates that the rear of
the second wafer from the front is used for this particular
switching function.
Circuit Boards. Figs. 4-8 through 4-17 show the circuit
boards used in the Type 422. Fig. 4-7 shows the location of
each board within the instrument. Each electrical compo
nent on the boards is identified by its circuit number. The
circuit boards are also outlined on the diagrams with a blue
line. These pictures, used along with the diagrams, aid in
locating the components mounted on the circuit boards.
Wiring Color-Code. All insulated wire and cable used in
the Type 422 is color-coded to facilitate circuit tracing.
Signal carrying leads are identified with one or two colored
stripes. Voltage supply leads are identified with three
stripes to indicate the approximate voltage using the EIA
resistor color-code. A white background color indicates a
positive voltage and a tan background indicates a negative
voltage. The widest color stripe identifies the first color of
the code. Table 4-2 gives the wiring color-code for the
power-supply voltages used in the Type 422.
TABLE 4-2
Power Supply Wiring Color Code
Supply
Background
color
First
stripe
Second
stripe
Third
stripe
—110 volt
Tan
Brown
Black
Brown
—81 volt
Tan
Gray
Black
Black
-1 2 volt
Tan
Brown
Red
Black
+10.5 volt
White
Violet
Green
Black
+12 volt
White
Brown
Red
Black
+55 volt White
Green
Green
Black
+95 volt
White
Brown
Black
Brown
Resistor Color-Code. In addition to the brown composi
tion resistors, some metal-film resistors and some wire-
wound resistors are used in the Type 422. The resistance
values of wire-wound resistors are printed on the body of
the component. The resistance values of composition resis
tors and metal-film resistors are color-coded on the compo
nents with EIA color-code (some metal-film resistors may
have the value printed on the body). The color-code is read
starting with the stripe nearest the end of the resistor. Com
position resistors have four stripes which consist of two
significant figures, a multiplier and a tolerance value (see
Fig. 4-2). Metal-film resistors have five stripes consisting of
three significant figures, a multiplier and a tolerance value.
Capacitor Marking. The capacitance values of common
disc capacitors and small electrolytics are marked in micro-
El
4-3
To Next Page
Loading...
