Tektronix 2235A Instruction Manual page 108

Maintenance
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2235A Instruction
Grid Coordinate System
Each schematic diagram and circuit board illustration
has a grid border alovg its left and top edges. A table
located adjacent to each diagram lists the grid
coordinates of each component shown on that diagram.
T o aid in physically locating components on the circuit
board, this table also lists the circuit-board grid
coordinates of each component.
Adjacent to each circuit board illustration is an alpha-
numeric listing of all components mounted on that
board. The second column in each listing identifies the
schematic diagram in which each component can be
found. These component-locator tables are especially
useful when more than one schematic diagram is
associated with a particular circuit board.
Troubleshooting Charts
The troubleshooting charts contained in the Diagrams
section are to be used as an aid in locating mal-
functioning circuitry. To use the charts, begin with the
Troubleshooting Guide. this chart will help identify a
particular problem area for further troubleshooting.
Note that some troubleshooting-procedure boxes on
each chart contain numbers along their lower edges.
These numbers identify the applicable schematic
diagram(s) to be used when performing the action speci-
fied in the box.
Both General and Specific notes may be called out in the
troubleshooting-chart boxes. These notes are located
on the inner panels of the foldout pages. Specific Notes
contain procedures or additional information to be used
in performing the particular troubleshooting step called
for in that box. General Notes contain information that
pertains to the overall troubleshooting procedure.
Some malfunctions, especially those involving multiple
simultaneous failures, may require more elaborate
troubleshooting approaches with references to circuit
descriptions in the Theory of Operation section of this
manual.
RESISTOR COLOR CODE. Resistors used in this
instrument are carbon-film, composition, or precision
metal-film types. They are usually color coded with the
EIA color code; however, some metal-film type resistors
may have the value printed on the body. The color code
is interpreted starting with the stripe nearest to one end of
the resistor. Composition resistors have four stripes;
these represent two significant digits, a multiplier, and a
tolerance value. Metal-film resistors have five stripes
representing three significant digits, a multiplier, and a
tolerance value.
CAPACITOR MARKINGS. Capacitance values of com-
mon disc capacitors and small electrolytics are marked
on the side of the capacitor body. White ceramic capaci-
tors are color coded in picofarads, using a modified EIA
code.
Dipped tantalum capacitors are color coded in
microfarads. The color dot indicates both the positive
lead and the voltage rating. Since these capacitors are
easily destroyed by reversed or excessive voltage, be
careful to observe the polarity and voltage rating when
replacing them.
DIODE COLOR CODE. The cathode end of each glass-
encased diode is indicated by either a stripe, a series of
stripes, or a dot. For most diodes marked with a series of
stripes, the color combination of the stripes identifies
three digits of the Tektronix Part Number, using the resis-
tor color-code system. The cathode and anode ends of
a metal-encased diode may be identified by the diode
symbol marked on its body.
Semiconductor Lead Configurations
Figure 9-2 in the Diagrams section shows the lead con-
figurations for semiconductor devices used in the instru-
ment. These lead configurations and case styles are
typical of those used at completion of the instrument
design. Vendor changes and performance improvement
changes may result in changes of case styles or lead
configurations. If the device in question does not appear
to match the configuration shown in Figure 9-2, examine
the associated circuitry or consult the semiconductor
manufacturer's data sheet.
Multipin Connectors
Component Color Coding
Multipin connector orientation is indexed by two
triangles; one on the holder and one on the circuit board.
Information regarding color codes and markings of
Slot numbers are usually molded into the holder. When a
resistors and capacitors is located on the color-codivg
connection is made to circuit board pins, ensure that the
illustration (Figure 9-1) at the beginning of the Diagrams
index on the holder is aligned with the index on the circuit
section. board (see Figure 6-1).
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ARTEK MEDU
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