Tektronix 535A, Instruction Manual

Page: 60 / 156

Calibration Procedure— Type 535A
TRIG. LEVEL CENTERING
1NT. TRIG.
D.C. LEVEL ADJ.
HIGH TEST POINT
TRIG. SENS.
C364
C375
C33O
LOCKOUT LEVEL
ADJ.
Fig. 6-3. Top View of the oscilloscope showing locations of internal controls.
To check the above supplies for proper regulation, vary the
autotransformer voltage between 105 v and 125 v (or from
210 v to 250 v if the power transformer is connected for
234 v operation). All of the regulated voltages should re­
main essentially constant.
The ripple present on any of the regulated supplies, as
measured with a test scope at the voltage check points, will
be well under 10 mv., with AMPLITUDE CALIBRATOR-OFF,
and neither sweep operating.
2. AMPLITUDE-CALIBRATOR Adjustment
The Cal. Adj. control should be set to provide a de out­
put of 100 volts when the AMPLITUDE CALIBRATOR switch
is in the OFF position. Under these conditions, the calibrator
output will be within 3% of the front-panel readings.
To make this adjustment connect the voltmeter between
the Cai. Test Pt. jack and ground (see Right Side View,
Fig. 6-2), turn the AMPLITUDE CALIBRATOR switch to the
OFF position, and adjust the Cal. Adj. control for a reading
of exactly 100 volts. To assure suitable symmetry of the
calibrator waveform, the reading at this point should not
be less than 45 v nor more than 55 volts when the cali­
brator is turned on (to any of the output voltage settings).
Readings outside this range are generally caused by un­
balanced multivibrator tubes (V875 or V885A).
3. High-Voltage Power Supply Adjustment
This adjustment determines the total accelerating poten­
tial on the crt, and thus affects the deflection sensitivity.
Connect the voltmeter between ground and the high-
voltage check point (see Top-View, Fig. 6-3), and set the H.
V. Ad|. (see Right Side View, Fig. 6-2) for a meter reading
of exactly — 1350 volts, if your meter has a full scale read­
ing of 1200 v, you can connect the positive meter lead to
the — 1 50 v supply, at any convenient point, and set the H.V.
Adj. for a meter reading of —1200 v
4. CRT Alignment
If the crt has been replaced, or if, due to considerable
handling, the trace does not align with the graticule, you
should make this adjustment before proceeding with the
calibration.
With no vertical signal applied, free run TIME BASE A, by
6-3