Adjustment Procedure - Tektronix 53C Instruction Manual

ADJUSTMENT PROCEDURE

The following outline is based on the adjust ­
ment procedure used in our test department
here at the factory. Ordinarily, adjustment in
the field will consist of touching up some of the
dc level and balance controls as outlined in the
OPERATING INSTRUCTIONS, but if a re ­
adjustment of the transient response is ever
necessary there is a certain sequence that should
be followed.
The input capacitance of the unit is accurately
set to 20 µµf at the factory. This insures that a
properly adjusted probe can be used interchange ­
ably with other units having 20-µµf input capaci ­
tance. To preserve this feature, you will need to
do one of these things: (1) use a CS-20 Input-
Capacitançe Standardizer, (2) calibrate a P400-
Series probe against a plug-in unit known to be
in correct adjustment, or (3) measure the input
capacitance with a Type 130 L,C meter or with
a capacitance bridge.
Peaking Coils
As a preliminary adjustment, set all peaking-
coil slugs so that the top of each slug is flush with
the bottom turn of the winding. (As an emergen ­
cy measure, these settings alone are adequate for
approximately correct results.)
For complete calibration of the peaking coils,
plug the Type 53/54C unit into a 540-Series oscil ­
loscope known to be in correct adjustment. Have
the cabinet or side panels removed. If the oscillo ­
scope is not of recent manufacture, you will have
to drill the side panel of the plug-in-preamplifier
compartment within the oscilloscope, to provide
access to the adjustments of the Type 53/54C
unit. A source of square waves or pulses having
a rise time not longer than 3 millimicroseconds is
needed. The repetition rate should preferably be
1 kc or more. It is essential that this source be
terminated in accordance with the manufacturer ' s
specifications.
Turn the MODE switch to A ONLY, the
VOLTS/CM switch to 0.05, and the VARI ­
ABLE control full right to the CALIBRATED
position.
The peaking coils affect the rise and leading
corner of the square wave and should be ad ­
justed for a square comer with no overshoot.
1. Adjust L3523 and L4413.
2. Adjust L3313 and L3353.
3. Adjust L3073 and L3253.
Move the square-wave source to the CHAN ­
NEL B input connector and set the B-channel
controls as you previously set the A-channel
controls.
1. Adjust L4313 and L4353.
2. Adjust L4073 and L4253.
If after adjustment one channel seems to have
a better response than the other try a slightly
different setting of L3523 and L4413, which are
common to both channels, and then repeat steps
2 and 3 of the A-channel adjustment and steps
1 and 2 of the B-channel adjustment. You will
have to experiment with the settings of L3523
and L4413 to find which setting will give the
best balance of response.
There are two types of adjustments to be made.
Each adjustment requires a Type 105, or other
square-wave source having a rise time not longer
than 0.025 µsec. The source must be terminated
according to the manufacturer ' s specifications.
One type of adjustment is made to compensate
the attenuators so the ac attenuation is equal to
the dc attenuation. This involves a moderately
short time constant. Misadjustment can be rec ­
ognized as a slight rounding or overshoot at the
leading corner of the square wave.
The other type of adjustment is made to get
equal input capacitances at all positions of the at ­
tenuator. Misadjustment can be recognized as a
downward or upward slope over about the first
one-quarter of the square wave.
First compensate the A-channel attenuators.
Connect the probe to the CHANNEL A input
connector and connect the square-wave source
to the probe. Display four or five cycles of a
1-kc square wave. Set the VOLTS/CM switch
to .05 and adjust C3023 for a flat top on the
square wave. Remove the probe and connect
the square-wave source to the input connector.
Adjust the listed capacitors for a square corner
on the square wave.
Connect the probe to the CHANNEL A input
connector and connect the square-wave source
to the probe. Adjust the input capacitance with
the VOLTS/CM switch in the positions shown.
5S/54C — MAINTENANCE — PAGE 2
Input Attenuators
VOLTS/CM Capacitor
.1
.2
.5
1
2
5
10
20
Capacitor
VOLTS/CM
.1
.2
.5
1
C4823C
C4833C
C4843C
C4853C
C4863C
C4873C
C4883C
C4893C
C4823B
C4833B
C4843B
C4853B