Tektronix 2236, Instruction Manual

Page: 137 / 350

4. Allow the CTM board assembly to air dry.
LUBRICATION
Most of the potentiometers used in this instrument are
permanently sealed and generally do not require periodic
lubrication. All switches, both rotary- and lever-type, are in­
stalled with proper lubrication applied where necessary and
will rarely require any additional lubrication. Therefore, a
regular periodic lubrication program for the instrument is not
recommended.
SEMICONDUCTOR CHECKS
Periodic checks of the transistors and other semiconduc­
tors in the oscilloscope are not recommended. The best
check of semiconductor performance is actual operation in
the instrument.
Maintenance— 2236 Service
PERIODIC READJUSTMENT
To ensure accurate measurements, check the perfor­
mance of this instrument after every 2000 hours of opera­
tion, or if used infrequently, once each year. In addition,
replacement of components may necessitate readjustment
of the affected circuits.
Complete Performance Check and Adjustment instruc­
tions are given in Section 4 and 5. The Performance Check
Procedure can also be helpful in localizing certain trouble in
the instrument. In some cases, minor problems may be re­
vealed or corrected by readjustment. If only a partial adjust­
ment is performed, see the interaction chart, Table 5-1, for
possible adjustment interactions with other circuits.
TROUBLESHOOTING
INTRODUCTION
Preventive maintenance performed on a regular basis
should reveal most potential problems before an instrument
malfunctions. However, should troubleshooting be required,
the following information is provided to facilitate location of
a fault. In addition, the material presented in the “Theory of
Operation” and the “Diagrams” sections of this manual may
be helpful while troubleshooting.
TROUBLESHOOTING AIDS
Schem atic Diagram s
Complete schematic diagrams are located on tabbed
foldout pages in the “Diagrams” section. The portions of
circuitry that are mounted on each circuit board are en­
closed within heavy black lines. Also within the black lines,
near either the top or the bottom edge, are the assembly
number and name of the circuit board.
Component numbers and electrical values of compo­
nents in this instrument are shown on the schematic dia­
grams. Refer to the first page of the “Diagrams” section for
definitions of the reference designators and symbols used to
identify components.
Circuit Board Illustrations
Circuit board illustrations (showing the physical location
of each component) are provided for use in conjunction with
each schematic diagram. Each board illustration can be
found on the back side of a foldout page, preceding the
schematic diagram(s) to which it relates. If more than one
schematic diagram is associated with a particular circuit
board, the board illustration is located on a left-hand page
preceding the diagram with which the board is first
associated.
Also provided in the “Diagrams” section is an illustration
of the bottom side of the Main circuit board. This drawing
facilitates troubleshooting by showing the connection pads
and the location of components that are mounted on the top
side of the board. Probing of Main board component signals
that are inaccessible from the top side can be achieved with­
out the necessity of disassembling portions of the
instrument.
Waveform test-point locations are also identified on the
circuit board illustration by hexagonal-outlined numbers that
correspond to the waveform numbers appearing on both the
schematic diagram and the waveform illustration.
6-5