Tektronix CURVE-TRACER 576 Instruction Manual page 82

Maintenance-Type 576
circuit diagrams are voltages and waveforms which can be
expected at various points in the circuitry. A block diagram
and other information concerning the major circuits in the
instrument are included at the beginning of the diagram
foldouts.
Electrical Parts List. The electrical parts list contains a
complete list of all the electrical components within the
instrument in the order of their circuit numbers. A com-
ponent description is also included for each part which pro-
vides: The Tektronix part number and electrical value (or
substitute part number); and tolerance. Instructions for
ordering replacement parts is provided at the beginning of
the Electrical Parts List section.
Calibration Procedure. The Performance Check/Calibra-
tion section also provides an adjustment procedure which
covers all the internal adjustments in the instrument. See
the Performance Check/Calibration Record and Index in
Table 5-2 for a list of the internal adjustments. The Per-
formance Check/Calibration section provides a performance
check procedure which will help determine whether a mal-
function is due to improper calibration or to a circuit or
component malfunction.
Circuit Description. A circuit description of each circuit
in the instrument with accompanying block diagrams is pro-
vided in the Circuit Description section. This section is
helpful when the source of a malfunction cannot be deter-
mined from the diagrams or the performance check/cali-
bration procedure. Also included is a block diagram descrip-
tion that gives the theory of operation of the instrument.
Circuit Boards. Fig. 4-6 through Fig. 4-28, at the rear of
this section, show all the circuit boards in the Type 576.
The electrical components on each of these pictures are
identified by their circuit numbers.
Wiring Color Code. All insulated wire and cable used in
the Type 576 is color-coded to facilitate circuit tracing.
Signal carrying leads have white backgrounds with one or
two colored stripes. The signal carrying wire color-codes are
given in Fig. 4-6 through 4-28 with the appropriate pin
connection. Power supply leads have either a red back-
ground (positive supply) or a purple background (negative
supply). Each power supply lead also has one colored stripe
which represents its ordinal relationship to the other
supplies having the same polarity, using the E lA resistor
color code. Table 4-1 gives the wiring color-code for the
power supply voltages used in the Type 576.
Power Cord Conductor Identification
Conductor Color Alternate Color
Ungrounded (Line)
Brown Black
Grounded (Neutral) Blue White
Grounding (Earthing) Green-Yellow Green-Yellow
4-2
TABLE
4-1
Power Supply Wiring Color
Supply Background Stripe
Color
Color
-75 volt Purple Red
-12.5 volt Purple Black
Var +4.5 volt Brown (none)
+5 volt Red Black
+12.5 volt
Red Brown
+50 volt
Red Yellow
+15volt
Red
Orange
+100 volt
Red
Green
+225 volt
Red
Blue
-4 kV
White
Purple
Ground
Black
(none)
Switch Wafer Identification. Switch wafers shown on
the diagrams are coded to indicate the position of each
wafer in the complete switch assembly. The numbered por-
tion 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 by 2R indicates that the rear
of the second wafer (from the front) is used for this parti-
cular switching functi"on.
Resistor Color Code. In addition to the brown composi-
tion resistors, some metal-film resistors (identifiable by
their gray body color) and some wire-wound resistors
(usually light blue or dark gray) are used in the Type 576.
The resistance value of a wire-wound resistor is printed on
the body of the component. The resistance value of a com-
position resistor or metal-film resistor is color-coded on the
component with E lA 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.
Composition resistors have four stripes which consist of
two significant figures, a multiplier and a tolerance value
(see Fig. 4-1). Metal-film resistors have five stripes con-
sisting of three significant figures, a multiplier and a toler-
ance value.
Capacitor Marking. The capacitance value of a common
disc capacitor or small electrolytic is marked in microfarads
on the side of the component body. The white ceramic
capacitors used in the Type 576 are color-coded in pico-
farads using a modified EIA code (see Fig. 4-1).
Diode Color Code. The cathode end of each glass
encased diode is indicated by a stripe, a series of stripes or a
dot. For most silicon or germanium diodes with a series .of
stripes, the color-code identifies the Tektronix Part Number
using the resistor color-code system (e.g., a diode color-
coded blue or pink-brown-grey-green indicates Tektronix
Part Number 152-0185-00). The cathode and anode ends of
REV. D, JUNE, 1976
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