Tektronix 485, Инструкция по эксплуатации

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Maintenance—485/R485 Service
Visual Inspection
The 485 should be inspected occasionally for such
defects as broken connections, broken or damaged ceramic
strips, 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 indi­
cates other trouble in the instrument; therefore, it is
important that the cause of overheating be corrected to
prevent recurrence of the damage.
Semiconductor Checks
Periodic checks of the semiconductors in the 485 are not
recommended. The best check of semiconductor per­
formance is actual operation in the instrument. More details
on checking semiconductor operation are given under
troubleshooting.
Recalibration
To ensure accurate measurements, check the calibration
of this instrument after each 1000 hours of operation or
every six months if used infrequently. In addition, replace­
ment of components may necessitate recalibration of the
affected circuits. The calibration procedure can also be
helpful in localizing certain troubles in the instrument. In
some cases, minor troubles may be revealed and/or
corrected by recalibration.
An elapsed-time meter is installed on the rear panel. This
meter provides a full-scale indication of 5,000 hours of
operating time and can be used to indicate when recalibra­
tion is necessary. Each minor division on this meter
indicates 200 hours of operation. When the elapsed-time
meter reaches 5,000 hours (full scale), it should be
replaced.
TRO U B LESH O O TIN G
Introduction
The following information is provided to facilitate
troubleshooting o f the 485. Information contained in other
sections of this manual should be used along with the
following information to aid in locating the defective
component. An understanding of the circuit operation is
helpful in locating troubles, particularly where integrated
circuits are used. See the Circuit Description section for this
information.
Troubleshooting Aids
Diagrams. Complete circuit diagrams are given on fold-
out pages in the Diagrams section. The component number
and electrical value of each component in this instrument
are shown on the diagrams (see first page of the Diagrams
section for definition of the reference designators used to
identify components in this instrument). Each main circuit
is assigned a series of component numbers. Table 4-1 lists
the main circuits in the 485 and the series of component
numbers assigned to each. Important voltages and wave­
forms are also shown on the diagrams. The portions of the
circuit mounted on circuit boards are enclosed with blue
lines.
TABLE 4-1
Component Numbers
Diagram
Number Circuit
Component
Numbers
On Diagrams
1
ATTEN
1-199
2 PREAMPS
200-399
3
VERT SW
400-499
4 TRIG AMP
500-599
5 VERT AMP
600-699
6 A TRIG GEN
700-849
7 A TIME-BASE
850-999
8
B TRIG GEN
1000-1149
9
B TIME-BASE 1200-1299
10 TIMING SW
1400-1479
11 HORIZONTAL AMP
1300-1399,
1150-1199
12 LOGIC
1500-1599
13 CRT
1600 1799
14
POWER INVERTER
1800 1849,
1900-1959
15 POWER SUP
2000-2099
16 CALIBRATOR & FAN
1480-1499,
2100-2139
Circuit Boards. Circuit board assembly numbers are
used ,on the diagrams and in the parts list to aid in locating
the boards. Pictures of the circuit boards are located in the
Diagrams section, on the back of the page opposite the
circuit diagram, to aid the cross-referencing between the
diagrams and the circuit-board pictures. Each electrical
component on the boards is identified by its circuit
REV. B. SEPT. 1974
4-3