Tektronix 53C, Instruction Manual

Page: 4 / 20

OPERATING INSTRUCTIONS
FIRST-TIME OPERATION
Plug the unit into a 540- or 530-Series Oscil­
loscope and turn the power on. Allow the instru­
ment to reach operating temperature, about 2 to
3 minutes and free-run the sweep at 1 millisec-
ond/cm. Turn the MODE switch to A ONLY
and the A-channel POLARITY and AC-DC
switches to NORMAL and DC respectively.
Position
the trace to about +2 cm with the A-
channel
VERTICAL POSITION control.
Turn the MODE switch to B ONLY and the
B-channel POLARITY and AC-DC switches
to NORMAL and DC respectively. Position
the trace to about —2 cm with the B-channel
VERTICAL
POSITION control.
Now turn the MODE switch to CHOPPED.
Two traces will appear on the crt screen. Notice
that the A-channel VERTICAL POSITION
control moves the upper trace and the B-channel
VERTICAL
POSITION control moves the
lower trace. Increase the sweep speed to 100
microsecond/cm and notice that each trace is
composed of many short-duration elements. The
two channels are being switched at approxi­
mately 100 kc so that each channel conducts for
about 5 µsec and then is cut off while the other
channel conducts for an equal time.
Now turn the MODE switch to the ALTER­
NATE position. There are still two traces on
the crt screen but
the traces are no longer chop­
ped into small bits. For each sweep cycle one
channel is conducting and the other is cut off.
The channels are switched at the end of each
sweep cycle.
GENERAL OPERATION
Either of the two identical amplified channels
can be used independently by turning the
MODE Switch to A ONLY or B ONLY and
connecting the signal to be observed to the ap­
propriate input. The following remarks apply
equally well to either amplifier channel.
Use of Probe
The Type P410 probe, furnished with the 540-
Series Oscilloscopes, is designed to preserve the
transient
response of this unit. This probe in­
troduces no ringing but causes an additional fre­
quency-response loss of less than 1 db at 24 me.
The
Type P410 probe has a 10-to-l attenuation
ratio.
The Type P510A probe is not suitable for use
with the Type 53/54C Plug-In Unit and 540-
Series Oscilloscope combination to observe fast­
rising pulses. This probe tends to ring at about
50 me and the wide passband of the 53/54C —
540-Series combination will display any ringing
that may occur.
Be
sure to check the adjustment of the probe
when you first connect it to a plug-in unit or
oscilloscope. The probe compensation is a func­
tion of the shunt input capacitance of the par­
ticular plug-in
unit or oscilloscope that you use
the probe with. If the compensation is incorrect
the frequency response will be affected. Touch
the probe tip to
the calibrator output connector
and display several cycles of the calibrator wave­
form.
If the top and bottom of the displayed
square wave are not flat, adjust the trimmer ca­
pacitor located either inside the probe body or
inside the box at the other end of the cable to
achieve correct square-wave response.
Input Coupling
It is sometimes undesirable to display the de
level of the waveform being observed. Placing
the AC-DC switch in the AC position inserts a
capacitor
in series with the input so the de com­
ponent of the waveform is blocked and only the
ac component is displayed. The low-frequency
response is about 2 cps when ac coupling is used.
Output
Polarity
It will be desirable to invert the displayed
waveform at times, particularly when using the
dual-trace feature of the 53/54C. The POLAR­
ITY switch has two positions. In the NORMAL
position the displayed waveform will have the
same polarity as the input signal. In the IN­
VERTED position the displayed waveform will
be turned upside down; that is, a positive-going
pulse will be displayed as a negative-going pulse.
DC Balance
Adjustment
After the plug-in unit has been in use for a
period of time you will notice that the trace will
change position as the VARIABLE control is
rotated. This is caused by tube ageing and the
resultant shift in operating potentials. To cor­
rect this condition rotate the VARIABLE con­
trol back and forth and adjust the DC BAL con­
trol until the trace position is no longer affected
by rotation of the VARIABLE control.
Gain Adjustment
Ageing of the tubes will also affect the gain
of the plug-in unit. Display a calibrator wave­
form of 0.2 volt peak to peak with the
VOLTS/CM
switch in the .05 position. Adjust
the GAIN ADJ control until the displayed
waveform
is 4 graticule divisions in amplitude.
Make sure the VARIABLE control is turned
full right to the CALIBRATED position before
making this adjustment.
53/54C — OPERATING INSTRUCTIONS — PAGE 1