Maintenance-2225 Service
Functional blocks on schematic diagrams are out-
lined with a wide grey line. Components within the
outlined area perform the function designated by the
block label. The Theory of Operation uses these
functional block names when describing circuit
operation as an aid in cross-referencing between
the theory and the schematic diagrams.
Component numbers and electrical values of
components in this instrument are shown on the
schematic diagrams. Refer to the first page of the
Diagrams section for the reference designators and
symbols used to identify components. Important
voltages and waveform reference numbers
(enclosed in hexagonal-shaped boxes) are also
shown on each diagram. Waveform illustrations are
located adjacent to their respective schematic
diagram.
Circuit Board Illustrations
Circuit board illustrations showing the physical
location of each component are provided for use in
conjunction with each schematic diagram. Each
board illustration is found in the Diagrams section on
the back of a foldout page, preceding the first sche-
matic
diagram(s) to which it relates.
The locations of waveform test points are marked on
the circuit board illustrations with hexagonal outlined
numbers corresponding to the waveform numbers
on both the schematic diagram and the waveform
illustrations.
Also provided in the Diagrams section is an illus-
tration of the bottom side of the Main circuit board.
This illustration aids in troubleshooting by showing
the connection pads for the components mounted
on the top side of the circuit board. By using this
illustration, circuit tracing and probing for voltages
and signals that are inaccessible from the top side of
the board may be achieved without dismantling
portions of the instrument.
Circuit Board Locations
The placement of each circuit board in the instru-
ment is shown in board locator illustrations. These
illustrations are located on foldout pages along with
the circuit board illustration.
Circuit Board Interconnections
A circuit board interconnection diagram is provided
in the Diagrams section to aid in tracing a signal path
or power source between boards. All wire, plug, and
jack numbers are shown along with their associated
wire or pin numbers.
Power Distribution
A Power Distribution diagram is provided to aid in
troubleshooting power-supply problems. This
diagram shows the service jumper connections used
to apply power to the various circuit boards.
Excessive loading on a power supply by a circuit
board fault may be isolated by disconnecting the
appropriate service jumpers.
Grid Coordinate System
Each schematic diagram and circuit board illus-
tration has a grid border along its left and top edges.
A table located adjacent to each diagram lists the
grid coordinates of each component shown on that
diagram. To aid in physically locating components
on the circuit board, this table also lists the grid
coordinates of each component on the circuit board
illustration.
Near each circuit board illustration is an alpha-
numeric listing of all components mounted on that
board. The second column in each listing identifies
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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.
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Component Color Coding
Information regarding color codes and markings of
resistors and capacitors is located on the
color-
coding illustration (Figure
9-1)
at the beginning of
the Diagrams section.
RESISTOR COLOR CODE.
Resistors used in this in-
strument are carbon-film, composition, or precision
metal-film types. They are usually color coded with
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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
Scans
by
ARTEK
MEDM
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