Tektronix 442, Инструкция по эксплуатации

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Maintenance— 442 Service
CRT. A blue plastic light filter is installed on the 442 at
the factory. Clean the light filter and the crt face with a soft
lint-free cloth dampened with denatured alcohol or a mild
detergent and water solution.
Visual Inspection
The instrument should be inspected occasionally for
such defects as broken connections, improperly seated
semiconductors, damaged or improperly installed circuit
boards, and heat-damaged parts.
The corrective procedure for most visible defects is
obvious; however, particular care must be taken if heat-
damaged components are found. Overheating usually
indicates other trouble in the instrument; therefore, it is
important that the cause of overheating be corrected to
prevent recurrence of the damage.
Lubrication
Most of the potentiometers used in the 442 are
permanently sealed and generally do not require periodic
lubrication. The switches used in the 442 (both cam- and
lever-type) are installed with proper lubrication applied
where necessary and will rarely require any additional
lubrication. A regular periodic lubrication programforthe
442 is not recommended.
Semiconductor Checks
Periodic checks of the transistors and other semicon­
ductors in the oscilloscope are not recommended. The
best check of semiconductor performance is actual
operation in the instrument.
Readjustment
To ensure accurate measurements, check the adjust­
ment of this instrument after each 1000 hours of operation
or, if used infrequently, every six months. In addition,
replacement of components may necessitate readjust­
ment of the affected circuits. The adjustment procedure
can also be helpful in localizing certain troubles in the
instrument. In some cases, minor troubles may be
revealed and/or corrected by readjustment. Complete
adjustment instructions are given in the Calibration
Procedure section.
TROUBLESHOOTING
Introduction
The following information is provided to facilitate
troubleshooting. Information contained in other sections
of this manual should be used along with the following
information to aid in locatingthe defective component. An
understanding of the circuit operation is helpful in
locating troubles, particularly where integrated circuits
are used. Seethe Theory of Operation, Section 3, for this
information.
Troubleshooting Aids
DIAGRAMS. Complete circuit diagrams are given on
foldout pages in the Diagrams section. The portions of the
circuit mounted on circuit boards are enclosed within
black lines. The component number and electrical value of
each component in this instrument are shown on the
diagrams. Important voltages and waveforms are also
shown on the diagrams. The physical locations of the
waveform test points are shown on the Circuit Board
illustrations.
CIRCUIT BOARD ILLUSTRATIONS. In conjunction
with each circuit diagram is a circuit board illustration.
These can be found on the back of a pullout page
preceding the circuit diagram to which it relates. Each
circuit component shown on the circuit diagram is
identified on the circuit board illustration by its compo­
nent number.
ADJUSTMENT LOCATIONS ILLUSTRATIONS. To
aid in locating test points and adjustable components, the
Adjustment Locations illustrations (in the Adjustment
Procedure portion of the Calibration Procedure) permit
rapid location of test points and adjustable components
because only these items are identified.
RESISTOR COLOR CODE. In addition to composition
resistors, some metal-film resistors and some wire-wound
resistors are used in the 442. The resistance values of wire-
wound resistors are usually printed on the body of the
component. The resistance values of composition
resistors and metal-film resistors are color coded on the
components with EIA 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 Figure 5-3). Metal-film resistors have
five stripes consisting of three significant figures, a
multiplier, and a tolerance value. For values of individual
resistors in thick-film resistor network assemblies, referto
the schematic diagram or the Replaceable Electrical Parts
list.
5-4
R E V A M A Y 1980