Tektronix 2230, Service Manual

Page: 34 / 483

Operating information— 2230 Service
If properly coded probes (IX, 10X, or 100X, see
Table 2-1) are connected to a channel input connec­
tor, the crt VOLTS/DIV readout will reflect the
correct deflection factor of the display.
Table 2-1
Probe Coding
Probe Coding Resistance
IX Infinite
10X 11 kfi ±10%
100X 5.6 kft -1 0 % to 6.2 k<l +10%
IDENTIFY
0 0 or none of the above
m
T ) Variable VOLTS/DIV Controls— Provide continu­
ously variable uncalibrated deflection factors
between the calibrated positions of the VOLTS/DIV
controls. The VOLTS/DIV sensitivity is reduced by
up to at least 2.5 times the sensitivity at the fully
counterclockwise position of the variable knob. A
detent at the fully clockwise position indicates the
calibrated VOLTS/DIV position of the variable knob.
The uncalibrated condition is indicated by a greater-
than symbol ( > ) in front of the affected VOLTS/DIV
readout.
^
2
) AC-GND-DC (Input Coupling) Switches— Select the
method of coupling the input signal to the CH 1 and
CH 2 vertical amplifiers and the storage acquisition
system.
AC—Capacitively couples the input signal to the
vertical deflection and signal acquisition systems.
The DC component of the input signal is blocked.
The lower — 3 dB bandpass is 10 Hz or less.
Selection of AC input coupling is indicated in the
readout by a tilde symbol (~) over the V on the
associated channel’s VOLTS/DIV readout.
GND—Grounds the input of the vertical amplifier;
provides a zero (ground) reference voltage display
(does not ground the input signal). In STORE
mode, the ground reference is acquired and
displayed in the first sample location of the
acquisition waveform display. When GND input
coupling is selected, a ground symbol is displayed
in the associated VOLTS/DIV readout.
DC— All frequency components of the input signal
are coupled to the vertical deflection and signal
acquisition systems. When DC input coupling is
selected, no additional indicators are displayed
with the associated VOLTS/DIV readout.
CH 1 OR X and CH 2 OR Y Input Connectors—
Provide for application of signals to the inputs of the
vertical deflection system and the storage acquisition
system.
Coding-ring contacts on each of the input connec­
tors are used to automatically switch the scale factor
displayed by the crt readout when a properly coded
probe is attached to the input connector. Displayed
STORE mode waveforms are reformatted to main­
tain the correct deflection as indicated by the
VOLTS/DIV readout on the affected channel(s). In
X-Y mode, the signal connected to the CH 1 OR X
input controls the horizontal deflection, and the sig­
nal connected to the CH 2 OR Y input controls the
vertical deflection.
(
1 4
) CH 2 INVERT Switch— Inverts the Channel 2 display
and STORE mode Channel 2 acquisition signal when
pressed in. An invert symbol (
1
) is displayed with the
CH 2 VOLTS/DIV readout when CH 2 is inverted.
With CH 2 inverted, the oscilloscope may be
operated as a differential amplifier when the Vertical
MODE of BOTH-ADD is selected.
( is ) VERTICAL MODE Switches— Select the mode of
v ' operation for the vertical amplifier. There are two
three-position switches and one two-position switch
that determine display and acquisition modes and
one two-position push-button switch that controls
the nonstore bandwidth.
CH 1— Selects only the Channel 1 input signal for
acquisition or display.
BOTH— Selects a combination of Channel 1 and
Channel 2 input signals for acquisition or display.
The CH 1-BOTH-CH 2 switch must be in the
BOTH position for ADD, ALT, and CHOP opera­
tion.
CH 2— Selects only the Channel 2 input signal for
acquisition or display.
ADD— Displays (NON STORE) or acquires and
then displays (STORE) the sum of the Channel 1
and Channel 2 input signals when BOTH is also
selected. The difference of the Channel 1 and
Channel 2 input signals is displayed (NON
STORE) or acquired and then displayed (STORE)
when the Channel 2 signal is inverted.
ALT— Alternately displays the nonstore Channel
1 and Channel 2 input signals. The nonstore alter­
nation occurs during retrace at the end of each
sweep. ALT Vertical MODE is most useful for
2-7