Tektronix 502A

SECTION 5
CALIBRATION
PROCEDURE
General Information
The instrument should not require frequent recalibration,
but occasional adjustments will be necessary when tubes
and other components are changed. Also, a periodic calibra 
tion is desirable from the standpoint of preventive main 
tenance.
Apparent troubles occurring in the instrument are often
actually the result of improper calibration of one or more
circuits. Consequently this section of the manual should be
used in conjunction with the Maintenance section during
troubleshooting work.
In the instructions that follow, the steps are arranged
in the proper sequence for a complete calibration of the
instrument. Each numbered step contains the information
required to make one adjustment or a series of related
adjustments.
In each calibration 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. All test
equipment, except for input signal sources, and all jumpers
are disconnected at the end of each step unless instructions
are given to the contrary. Input signal voltages should
remain connected to the instrument until specific instruc 
tions are given to disconnect them or until another input
signal is applied to the same input connector.
It will be necessary for you to refer to the calibration
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
adjustments in these circuits usually cannot be made. When
amplifier adjustments are required, the entire amplifier
should be calibrated. In addition, if either the — 150 volt
supply or the high voltage power supply is adjusted, the
entire instrument must be calibrated.
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 calibrate the entire circuit.
Equipment Required
The following equipment or its equivalent is necessary for
a complete calibration of the Type 502A 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 portable test meters have the required ac 
curacy, particularly after a period of use.
Fig. 5-1. Tools required for calibrating the Type 502A Oscilloscope.
2. Accurate rms-reading ac voltmeter, 0-150 volts (0-250
or 0-300 volts for 210- to 250-volt operation).
3. Variable autotransformer, having a rating of at least
500 watts.
4. Time-mark generator, Tektronix Type 180A or 181. If
neither of these instruments is available, it will be necessary
to substitute a time-mark generator having markers at 1
microsecond, 5 microsecond, 10 microsecond, 50 microsecond,
100 microsecond, and 1 millisecond intervals.
5. Square-wave generator, Tektronix Type 105. If a Type
105 Square-Wave Generator is not available, it will be
necessary to substitute a square-wave generator with the
following specifications: (1) output frequencies of 200 cycles,
1 kilocycle, and 10 kilocycles, (2) rise-time no more than
20 nanoseconds, and (3) output amplitude variable between
approximately 40 millivolts and approximately 100 volts.
6. Oscilloscope, Tektronix Type 316 or 317. If a Type 316
or 317 Oscilloscope is not available, it will be necessary to
substitute an oscilloscope with the following specifications:
(1) calibrated vertical deflection factors from .01 to 10
volts per division and (2) bandpass of d c to 10 megacycles.
7. 50-ohm, 42 inch Coaxial Cable (1)
8. Tektronix 50-ohm Termination Resistor. (2)
9. Tektronix Type 5XT, 50-ohm T-Pad. (2)
10. Tektronix 47 pf Input Time Constant Standardizer,
Tektronix part number 011-030 (1).
11. Tektronix Type 10XT, 50-ohm T-Pad. (1)
12. Coaxial "T" Connector. (1)
5-1