Maintenance— 2445 Service
Troubleshooting Charts
The troubleshooting charts contained in the “Diagrams”
section are to be used as an aid in locating malfunctioning
circuitry. To use the charts, begin with the Preliminary Tests
flowchart. This chart will help identify problem areas and will
direct you to other appropriate charts for further
troubleshooting.
Some malfunctions, especially those involving multiple si
multaneous failures, may require more elaborate trouble
shooting approaches with references to circuit descriptions
in the “Theory of Operation” section of this manual.
Component Color Coding
Information regarding color codes and markings of resis
tors 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 instru
ment 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. Composi
tion resistors have four stripes; these represent two signifi
cant digits, a multiplier, and a tolerance value. Metal-film
resistors have five stripes representing three significant dig
its, 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 capacitors 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 resistor color-
code system. The cathode and anode ends of a metal-en
cased 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. Ven
dor 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 configura
tion shown in Figure 9-2, examine the associated circuitry or
consult a manufacturer’s data sheet.
Multipin Connectors
Multipin connector orientation is indexed by two trian
gles; one on the holder and one on the circuit board. Slot
numbers are usually molded into the holder. When a con
nection is made to circuit board pins, ensure that the index
on the holder is aligned with the index on the circuit board
(see Figure 6-1).
(
0 9 9 5
-
1 1
)
2662-5 0
Figure 6-1. Multipin connector orientation.
TROUBLESHOOTING EQUIPMENT
The equipment listed in Table 4-1 of this manual, or
equivalent equipment, may be useful when troubleshooting
this instrument.
TROUBLESHOOTING TECHNIQUES
The following procedure is arranged in an order that en
ables checking simple trouble possibilities before requiring
more extensive troubleshooting. The first two steps use di-
6-6
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