Tektronix 543B, Instruction Manual

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Calibration — Type 543B/RM543B
voltage 10% above and below the design center line volt­
age. From the stable trace position at low-line voltage to
a possible new stable position at high-line voltage, the trace
should not drive more than 0.5 cm.
7. Checking Alternate Trace and Chopped Blanking
Set the AMPLITUDE CALIBRATOR to 20 VOLTS and the
Type TU-7 Test Function switch to Alternate. Connect a
jumper from the CAL OUT to the Ext Input connector of the
TU-7. Center the display with the Vertical Position control
and check each sweep rate of the TIME/CM switch for
the alternating traces.
When observing slow sweep rates, the spot will consist
of a single dot when the upper trace crosses the crt. How­
ever, the spot will consist of two dots, one above the other,
when the lower trace crosses the crt.
Set the Type TU-7 Test Function switch to Chopped and
the TIME/CM control to 5 μSEC. Adjust the triggering con­
trols for a stable display. Switch the CRT CATHODE SELEC­
TOR to CHOPPED BLANKING and observe that the vertical
lines (chopped transients) disappear. Return the CRT CATH­
ODE SELECTOR switch to the EXTERNAL CATHODE posi­
tion and reset the oscilloscope and Type TU-7 controls
according to Table 5-1.
TABLE 5-1
Crt Controls
Usable level
As is
As is
As is
Time Base
INTENSITY
FOCUS
ASTIGMATISM
SCALE ILLUM
TRIGGERING LEVEL
STABILITY
TRIGGERING MODE
TRIGGER SLOPE
VARIABLE (TIME/CM)
TIME/CM
HORIZONTAL DISPLAY
SINGLE SWEEP
0
Clockwise
AUTO
+EXT
CALIBRATED
.5 mSEC
NORMAL (X 1)
NORMAL SWEEP
Other Controls
HORIZONTAL POSITION
VERNIER (HORIZONTAL
POSITION)
EXTERNAL HORIZONTAL
VOLTS/CM
VARIABLE (EXTERNAL
HORIZONTAL VOLTS/
CM)
AMPLITUDE CALIBRATOR
Midrange
Midrange
10
CALIBRATED
100 VOLTS
TU-7
Vertical Position Centered
Test Function Gain Set
Other Controls As is
TRIGGERING ADJUSTMENTS
8. Trigger Sensitivity
With no input leads connected to the Type TU-7 and the
front-panel controls set as in Table 5-1, connect a probe
from the test oscilloscope to the junction of C131 and R49
and a jumper from the TRIGGER INPUT connector to
ground. Set the test oscilloscope sweep rate for 10 msec/
cm, the vertical controls for ac coupling and input signal of
5 volts in amplitude, and the triggering controls for a stable
display.
Adjust the TRIG SENS control until one cycle of the wave­
form occupies about 2.5 cm of the sweep. Disconnect the
jumper between the TRIGGER INPUT connector and ground.
9. Trigger Level Centering
Set the TRIGGER SLOPE control to +INT and the TRIG­
GERING MODE switch to AC. Connect a test lead from the
CAL OUT connector to the Ext Input connector on the Type
TU-7. A signal with an amplitude of 4 cm should be ob­
served. If this signal amplitude is not present recheck steps
2 and 6. After observing the 4-cm signal, reduce rhe AMPLI­
TUDE CALIBRATOR signal to 5 volts to obtain a calibrated
2-mm signal for use in the following procedure,
Center the trace vertically on the crt and adjust the
INTENSITY, FOCUS and ASTIGMATISM controls for best
definition. Then ground the junction of R19 and R20 with a
short clip lead. This junction is located on top of the trigger
switch (see Fig. 5-3).
Preset the TRIG LEVEL CENTERING control fully clock­
wise. Turn the STABILITY control counterclockwise until the
trace just disappears from the crt screen, then two or three
degrees further counterclockwise.
Turn the TRIG LEVEL CENTERING control counterclock­
wise until the display reappears on the crt. Then switch the
TRIGGER SLOPE control to —INT; it may be necessary to
turn the TRIG LEVEL CENTERING control clockwise slight­
ly to obtain a stable display. Then while switching back and
forth between +INT and —INT, slightly readjust the TRIG
LEVEL CENTERING control for sfab'e triggering in both
positions.
10. Internal Triggering Dc Level
Set the Type TU-7 Test Function switch to Low Load and
the oscilloscope AMPLITUDE CALIBRATOR to 1 VOLT. Use
the Type TU-7 Variable control to reduce the signal ampli­
tude to 6 mm.
Center the display vertically, and turn the TRIGGERING
MODE switch to the DC position. While switching the
TRIGGER SLOPE control back and forth between +INT and
—INT, adjust the INT TRIG DC LEVEL ADJ control for stable
triggering in both positions. It may be necessary to slightly
readjust the TRIG LEVEL CENTERING control to obtain
stable triggering.
5-5