Troubleshooting Equipment; Troubleshooting Techniques - Tektronix 2205 Service Manual

Maintenance—2205 Service
Near each circuit board illustration is an alpha­
numeric listing of all components mounted on that
circuit board. The second column in each listing
identifies the schematic diagram in which each com­
ponent can be found. These component-locator ta­
bles are especially useful when more than one sche­
matic diagram is associated with a particular circuit
board.
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
instrument are carbon-film, composition, or pre­
cision metal-fiim 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 rep­
resent two significant digits, a multiplier, and a
tolerance value. Metal-fiim resistors have five
stripes representing three significant digits, a multi­
plier, and a tolerance value.
CAPACITOR MARKINGS. Capacitance values of
common plastic capacitors and small electrolytics
are marked on the side of the capacitor body.
Small, machine-insertable capacitors are numeri­
cally coded in picofarads. The first two numbers are
the significant digits and the third number (if a
three-number code) is the number of zeros fol­
lowing the digits. When there are two numbers
separated by the tetter "R ", the two numbers are
the significant digits; the letter marks the radix (deci­
mal point). Some examples of this type of capacitor
coding are as follows;
475 = 47 00000 pF = 4.7 j*F
472 = 47 00 pF = 0.0047 jiF
471 = 47 0 pF
470 = 47 pF
4R7 s s 4.7 pF
The code numbers may be difficult to locate and
read on installed parts. Capacitor values may be
found by referencing the circuit designation number
in the Replaceable Electrical Parts list.
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
6— 5
cathode and anode ends of a metal-encased diode
may be identified by the diode symbol marked on its
body.
Sem iconductor Lead Configurations
Figure 9-2 in the Diagrams section shows the
lead configurations for semiconductor devices used
in the instrument. These lead configurations and
case styles are typical of those used at completion
of the instrument design. Vendor changes and per­
formance 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 manufacturer's
data sheet.

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 enables checking simple trouble possibilities
before requiring more extensive troubleshooting.
The first four steps ensure proper control settings,
connections, operation, and adjustment. If the
trouble is not located by these checks, the re­
maining steps will aid in locating the defective com­
ponent. When the defective component is located,
replace it using the appropriate replacement pro­
cedure given under Corrective Maintenance in this
section.
i CAUTION ?
iv w v w w v u
Before using any test equipment to make
measurements on static-sensitive, current-
s sabslttve, or voltage-sensitive components or
assemblies, ensure that any voltage or
current supplied by the test equipment does
not exceed the limits of the component to be
tested.
1. Check Control Settings
Incorrect control settings can give a false indi­
cation of instrument malfunction. If there is any
question about the correct function or operation of
any control, refer to either the Operating Information
in Section 2 of this manual or to the Operators
Manual.