Tektronix 502 series, Instruction Manual

Page: 51 / 114

RECALIBRATION PROCEDURE
INTRODUCTION
The following paragraphs outline the proce­
dure used to recalibrate the Type 502 Oscillo­
scope. The instrument should not require fre­
quent recalibration, but occasional adjustments
will be necessary when tubes and other com­
ponents are changed. Also, a periodic recalibra­
tion is desirable from the standpoint of preventa­
tive maintenance.
Apparent troubles occuring in the instrument
are often actually the result of improper calibra­
tion of one or more circuits. Consequently this
section of the manual should be used in conjunc­
tion with the Maintenance section during trouble­
shooting work. If a trouble occurs in the instru­
ment, you must first be sure that the trouble is
not due to improper calibration before proceed­
ing with more detailed troubleshooting.
In the instructions that follow, the steps are
arranged in the proper sequence for a complete
recalibration of the instrument. Each numbered
step contains the information required to make
one adjustment or a series of related adjustments.
In each recalibration step only the required
information is given. Controls are assumed to
be set at the positions they were in during the
previous step unless specific instructions are
given to change their settings or unless different
settings are required to obtain a suitable display
on the face of the crt. All test equipment, except
for input signal sources, and all jumpers are dis­
connected at the end of each step unless instruc­
tions are given to the contrary. Input signal volt­
ages should remain connected to the instrument
until specific instructions are given to disconnect
them or until another input signal is applied to
the same input connector.
The location of the adjustment controls is
given on the pull out sheets immediately follow­
ing the Recalibration Procedure section.
If a single control requires adjustment, and
the particular control is known, it can often be
adjusted without necessitating a recalibration of
the entire instrument provided the control does
not interact with other adjustments. In such
cases the control is adjusted in the normal man­
ner as described in the applicable step of the
Recalibration Procedure. It will be necessary,
however, for you to refer to the recalibration
steps immediately preceding the adjustment you
wish to make to determine the proper settings
for the controls not mentioned in that step. Due
to the interaction between adjustments in the
horizontal and vertical amplifiers, single adjust­
ments in these circuits usually cannot be made.
When amplifier adjustments are required, the
entire amplifier should be recalibrated. In addi­
tion, if either the —150-volt supply or the high
voltage power supply is adjusted, the entire in­
strument must be recalibrated.
If you find that a circuit is out of calibration,
but you are not aware of which particular
adjustment will correct the difficulty, it is usually
best to recalibrate the entire circuit. For your
convenience, all the recalibration adjustments are
subdivided into their respective circuits so that
any one circuit can easily be recalibrated.
EQUIPMENT REQUIRED
The following equipment or its equivalent is
necessary for a complete recalibration of the
Type 502 Oscilloscope.
1. DC voltmeter (sensitivity of at least 5000 ohms
per volt) with corrected readings within 1 % for
100, 150, and 350 volts and within 3% for 2900
volts. Be sure your meter is accurate; few port­
able test meters have the required accuracy,
particularly after a period of use.
2. Accurate rms-reading ac voltmeter, 0-150 volts
(0-250 or 0-300 volts for 210- to 250-volt opera­
tion).
3. Variable autotransformer (Powerstat, Variac,
etc.) having a rating of at least 500 watts.
4. Time-mark generator, Tektronix Types 180 or
181. If neither of these instruments is available,
it will be necessary to substitute a time-mark
generator having markers at 1 microsecond, 10
microsecond, 100 microsecond, and 1 millisecond
intervals.
© RECALIBRATION PROCEDURE — TYPE 502
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