Tektronix 570, Manual

Page: 28 / 134

- 1.
2
-
-l.l
-.6
-.9
-
-.2
DIV
.2
VOL TS/DIV
Egr-
Control Settings for Pentode section of
a 6U8
PEAK VOLTS
SERIES LOAD
STEPS/SEC
VOLTS/STEP
START ADJUST
PLATE -GRID
PLATE-SCREEN -G�UD
M A/DlV
VOLTS/DlV
+DC
+ DC VARIABLE
100
50k
240
.1
o
GRID
GRID
.05
.2
50
Set for
31
volts
Fig.
2-12.
Grid Current
vs.
Grid Voltage curves for the pentode
section of
a 6UB.
and comes to rest is equivalent to about
14
s teps at any setting of the VOLTS/STEP
Control.
Thus , if the step generator is set
for the maximum number of positive steps
with the START ADJUST Control, it will rest
five steps negative until the S INGLE FAMILY
button is pushed. This will be between
.5
volts
and
50
volts negative depending on the setting
of the VOLTS/STEP Control. In many cases
this will not hold a tube cut off but it will
usually be in a safe operating region.
If
the
ST AR T ADJUST Control is backed off from its
most positive position the voltage at which the
grid rests can be increased up to a maximum
of
140
volts negative.
The current ratings of the + DC connection
and the Grid-Step Generator can also be safely
exceeded by use of the single-family feature.
The Grid-Step Generator will deliver a peak
c urrent of from
200
to
250
rna if a few seconds
are allowed between each presentation for
the circuits to recover. The + DC connection
will deliver
500
rna for a single family with
Ig
J
.5
MA/DlV
Eg]
. 1
.
2
20 VOL TS/DlV
Ep-
Control Settings for Pel1tode section of
a 6U8
PEAK VOLTS
200
SERIES LOAD
10k
STEPS/SEC
240
VOLTS/STEP
. 1
ST ART ADJUST
0
PLATE-GRID PLATE
PLATE -SCREEN-GRID
SCREEN
MA/DIV
.5
VOLTS/DlV
20
+DC
50
+DC VARIABLE Set for
35
volts
Fig.
2-13.
Screen Current vs. Plate Voltage curves for the pentode
section of
a
6UB.
a voltage drop of less than one volt. A second
or two is required for the+ DC circuits to recover
b efore a second family can be plotted.
SEMICONDUCTOR DEVICES
The Type
570
was designed fortesting vacuum
tubes. However , it is useful for plotting semi­
conductor diode characteristics and some tran s ­
istor characteristics.
Semiconductor diode curves are plotted in the
s arne way as vacuum tubes described under
Thermionic Diodes. To protect the diode ,
maximum resistance , as set by the SE RIES
LOAD Control , consistent with adequate voltage
swing as set by the PEAK VOLTS should be
used. If you connect the diode between the test
panel , P , connector and the + DC connector , be
sure to load the
+
DC
connection with an external
resistor. The + DC circuit will lose regulation
if current through the diode exceeds the current
through the resistor by more than
2
rna. This
resistor should be selected to draw
50
rna
o r less.
2-10
O perating Instructions - Type
570
AA