Drawings

The overall objective of the SIMM is to display more

As stated earlier in chapter 3, simplified schematics

descriptive and illustrative data per page; eliminate

normally omit parts and connections that are not

unnecessary words, discussion, and illustrations;

essential to understanding circuit operation. In studying

organize all required data so rapid access is afforded,

or troubleshooting equipment, the technician often

makes a simplified drawing, including only those items

and display complete circuit element dependencies as

simply as possible.

that contribute to the purpose of the drawing. When you

are using the schematic drawings in this manual,

The SIMM helps organize the technical details of an

technical manuals, textbooks, and other publications,

equipment or system, providing users with all the

notice the various techniques for simplifying

information the y need to learn to operate and maintain

schematics, thereby increasing their usefulness in

the equipment or system. The style of writing and the

maintenance work.

use of circuit-identifier codes (coding that assists

recognition of the circuit character) and coded symbols

DRAWINGS

enable the trainee to learn faster. Circuit diagrams and

associated text are presented on facing pages.

The drawings used by an IC Electrician include

The text is concise; yet it defines the circuit

block diagrams, signal flow charts, wiring diagrams,

operation precisely. Block diagrams relate the level of

and mechanical drawings. As with schematics, the IC

physical containment (unit, assembly, subassembly,

Electrician will be familiar with some drawings from

sub-subassembly) with the hardware to the functional

past experience. The use of block diagrams and signal

circuits. Associated text is likewise presented on a facing

flow charts to present the overall picture of equipment

page. Coded symbols and abbreviations indicate the

function is widespread. Although they do not contain the

kind of signals being processed, and circuit-identifier

details that are needed in accomplishing maintenance

codes identify the circuit represented by uniquely

tasks, they are obviously valuable in training situations

shaped blocks. Maintenance dependency charts, based

and in providing overall continuity when personnel are

upon positive logic, provide a unique, fast method of

working with partial schematics.

trouble analysis, include operating procedures, and

reveal to a degree the designed-in equipment

SYMBOLIC INTEGRATED

maintainability. The emphasis on symbology, a concise

MAINTENANCE MANUAL

writing style, and memory devices permit a reduction in

page count with no loss in technical content.

The IC Electrician is responsible for maintaining

many different types of complex electrical/electronics

The SIMM is developed around the following three

equipment, Usually, the diagnostic logic shortcomings

basic building blocks:

of a young maintenance force result in longer than

Blocked schematic

necessary equipment downtime. In some cases,

equipment damage is introduced by trial-and-error

Blocked text

maintenance actions. Some faults cannot be located and

repaired by the unit level maintenance personnel

Precise-access blocked diagram

because they lack experience or are not familiar with the

equipment. Then too, personnel of all experience levels

BLOCKED SCHEMATIC

are frequently transferred and encounter new

equipment. A relatively new troubleshooting aid, the

By definition, a blocked schematic is a schematic

Symbolic Integrated Maintenance Manual (SIMM),

diagram laid out in block form (fig. 4-1). It distinguishes

should help the troubleshooter identify more readily the

the functions and physical aspects of the hardware by

general location of a fault. Though this manual presents

using shaded areas of blue and gray. The blue-shaded

a rather complete circuit analysis, in no way does it

areas show the functional features of a circuit (lowest

prevent the requirement for local analysis and a

definable basic circuit, filter, voltage divider, oscillator,

well-informed technician. The SIMM represents a major

amplifier, relay contact, meter, coil, switch, and so on)

change in the methods of presenting technical data and

and the gray-shaded areas show the hardware (chassis,

the methods of diagnosing electronic system faults.

drawer, module, and so on).

Through the use of new information display techniques

and symbology, blocks, and color shading, the job of

Each blue area includes ALL circuit elements that

fault isolation in complex electronic systems is made

are involved in accomplishing the circuit function; these

easier, faster, and surer.

areas are called functional entities. Each functional

4-2