Tektronix CURVE-TRACER 576 Instruction Manual page 85

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2. Check Instrument Calibration. Check the calibration
. of this instrument or of the affected circuit if the trouble is
' known to exist in one particular circuit. The apparent
..,trouble may be only a result of misadjustment and may be
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corrected by calibration. Complew calibration instructions
are given in the Performance Check/Calibration section of
this manual.
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3. locating Malfunctioning Circuits. To locate the
source of a malfunction in instrument operation, the
trouble symptom will often indicate the identity of the
faulty circuit(s). For example, if a display of the Collector
Supply output can be obtained on the test oscilloscope
CRT but a display of the Step Generator output cannot be
obtained, the Step Generator is probably malfunctioning.
If the trouble symptom does not indicate which cir-
cuit(s) is causing problems (for example, if there were no
Collector Supply or Step Generator outputs), a more sys-
tematic troubleshooting procedure is necessary. Fig. 4-3
provides a general guide for locating the circuits which are
most likely causing the instrument to malfunction.
The following preliminary procedure ensures that the
instrument malfunction is not caused by improper control
settings and helps determine where to begin on the trouble-
shooting chart:
A.
Set the following Type 576 controls to:
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GRATICULE ILLUM
.,READOUT ILLUM
INTENSITY
Fully Clockwise
Fully Clockwise
Trace Visible
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FOCUS
VERTICAL
DISPLAY OFFSET Selector
CENTERLINE VALUE
HORIZONTAL
POSITION (Vert and Horiz)
FINE POSITION (Vert and Horiz)
ZERO
CAL
DISPLAY INVERT
MAX PEAK VOLTS
PEAK POWER WATTS
VARIABLE COLLECTOR
SUPPLY
POLARITY
MODE
LOOPING COMPENSATION
NUMBER OF STEPS
CURRENT LIMIT
AMPLITUDE
OFFSET
OFFSET MUL T
STEPS
PULSED STEPS
STEP FAMILY
RATE
\._,POLARITY INVERT
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STEPMULT.1X
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Centered
STEP GEN
NORM(OFF)
0
2 V COLLECTOR
Centered
Centered
Released
Released
Released
15
0.5
Fully Clockwise
+(NPN)
NORM
As Is
10
20 mA
2V
ZERO
0
Pressed
Released
REP
NORM
Released
Released
Terminal Selector
LEFT-OFF-RIGHT
Maintenance-Type 576
BASE TERM STEP
GEN
RIGHT
B. Turn on the Type 576 and allow a few minutes to
warm up.
C. CHECK FOR-Display of the Collector Supply sweep
of about 15 volts peak horizontally on the Type 576 CRT
graticule and of the Step Generator signal of one step per
division vertically.
D. If no display can be obtained or the display is incor-
rect, connect the 10X probe between the test oscilloscope
and the collector terminal on the right hand side of the
Standard Test Fixture (connect ground lead to emitter ter-
minal).
E. CHECK FOR-Display of Collector Supply output-
a positive-going full-wave rectified sine wave of about 15
volts peak on test oscilloscope CRT.
F. Connect the probe to the right base term ina I of the
Standard Test Fixture.
G. CHECK FOR-Display of Step Generator output of
positive-going steps of 2 volts/step on test oscilloscope
CRT.
H. Start with the following step on Fig. 4-3 according to
the results of the previous checks:
1. Step (A)-No Collector Supply output; Step Gen-
erator output or display on the Type 576 CRT.
2. Step (B)-No Collector Supply output or incorrect
output, but Step Generator is displayed on the Type 576
CRT.
3. Step (C)-No Step Generator output (or incorrect
output), but Collector Supply is displayed on the Type
576 CRT.
4. Step (D)-No display on type 576 CRT (or incor-
rect display), but Collector Supply output and Step Gen-
erator output are displayed properly on the test oscillo-
scope CRT.
After the defective circuit has been located using Fig.
4-3, proceed with steps 4 through 9 to locate and repair the
faulty components.
4. Visual Check. Visually check the portion of the in-
strument in which the trouble is located. Many troubles can
be located by visual indications such as unsoldered connec-
tions, broken wires, damaged circuit boards, damaged com-
ponents, etc
5. Check Circuit Board Interconnections. After the
trouble has been isolated to a particular circuit, check the
pin connectors on the circuit board for correct connection.
Figs. 4-6 through 4-28 show the correct connections for
each board.
The pin connectors used in this instrument also provide
a convenient means of circuit isolation. For example, if the
4-5