Iwarning - Tektronix 176 Instruction Manual

Operating I nstructions-176
that shown in Fig. 2-2. (The VERTICAL switch should be
set at one of its five highest current positions.)
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Fig. 2-2. Typical display of Ic vs V ce for 10 different steps of base
current for an NPN transistor.
11. Press the Type 576 OFFSET AID button and set
the OFFSET MUL T control for 2.00 (two steps of offset).
Note that the zero step (or pulse) of the display is no longer
on the zero horizontal graticule line. For normal pulsed
base operation of the Type 576 (with the X 10 STEP button
not illuminated) the offset voltage or current is not pulsed.
12. Press the 176 Xl0 VERT button, which should
illuminate the button. Note that the size of the vertical
display is decreased by 10 times due to the lOX increase in
the vertical deflection factor. The PE R VERT D IV readout
shou Id also increase by 10 times.
13. Press the X 10 STEP button, wh ich shou Id illu-
minate the button. Note that the size of the display in-
creases due to the 10 times increase in the step generator
step amplitude. The PER STEP readout should also increase
by 10 times, Also note that the offset is now pulsed; thus,
the pulses start from the zero horizontal line rather than
from the offset level as discussed in step 11 for normal
operation.
14. Lift the lid of the protective box. Note that the
collector supply interlock opens and disables the collector
2-6
supply. This causes the red WARNING light on the 176 to
go out, the yellow COLLECTOR SUPPLY VOLTAGE
DISABLE light on the Type 576 to go on, and the display
to disappear.
15. Leaving the lid of the protective box open, press the
176 INTERLOCK OVERRIDE button. This causes the
collector supply to be enabled. Note that when the button
is pushed, the yellow COLLECTOR SUPPLY VOLTAGE
DISABLE light goes out, the red WARNING light goes on
and ad isplay re-appears.
I
WARNING
I
Pressing the INTERLOCK OVERRIDE button when
the protective box is not in place enables the collector
supply and makes operation of the instrument
potentially dangerous. Operators should always be
aware that when the red WARNING light is on,
dangerous voltage may appear at the collector ter-
minal.
16. Release the INTERLOCK OVERRIDE button and
close the lid of the protective box.
17. Press the 1000 MAX PEAK POWER-WATTS
button. Note that the maximum peak power being dis-
sipated by the device under test (Ic versus V
CE )
increases.
18. Press the 176 10 MAX PEAK POWER-WATTS
button. Note that the maximum peak power decreases.
Press the 100 MAX PEAK POWER-WATTS button.
19. Set the Type 576 AMPLITUDE switch to 5 mAo
Note that the 176 X 10 STEP button light goes out, and the
step generator step amplitude is no longer multiplied by 10
times.
20. Set the Type 576 VERTICAL switch to 50 mAo
Note that the 176 X 10 VERT button light goes out, and
the vertical deflection factor is no longer multiplied by 10
times,
This completes the first time operation procedure.