Tektronix 570, Manual

Page: 25 / 134

I V .5 MA/D
0
10 VOL TS/DiV
Ep-
Control Settings for Triode section of
a
6U8
PEAK VOLTS
SERIES LOAD
STEPS/SEC
VOLTS/STEP
START ADJUST
PLATE -GRID
P LATE -SCREEN -GRID
MA/DIV
VOLTS/DiV
200
10k
240
. 1
full clockwise
PLATE
GRID
.5
10
Fig.
2-6.
Grid Current vs. Plate Voltage curves for the triode section
of a
6US.
Plate Current
vs.
Grid Voltage
To display plate current plotted against grid
voltage , set the controls as for the plate current
versus plate voltage curves and switch the
PL ATE-GRID Control to GRID. This
automatically positions the display to the right.
It will normally be necessary to increase the
horizontal sensitivity with the HORIZONTAL
VOL TS/DIV switch and reposition the display
s lightly.
The display obtained consists of vertical
lines which show the vari ation of plate current
as the plate is swept from zero to maximum
Voltage. The part of the curve of primary
interest is formed by the tops of these lines.
This is a dynamic
characteristic for the
combined tube and load resistance. However.
if the S E RIES LOAD is set to 300 the effect of
the load resistance is very slight.
The voltage from the Plate Sweep Generator
depends upon the line voltage and it is not
i ntended that the calibration of the PEAK VOLTS
Control be exact. If the actual peak plate
-2
-
1
.
8
-1.6
-1.4 -1.2
-1
-.8
2
MA/D IV
2
VOLTS/DiV
E-
g
-.6 - .4
-.2
Control Settings for Triode section of
a
6U8
PEAK VOLTS
SERIES LOAD
STEPS/SEC
VOLTS/STEP
START ADJUST
PLATE-GRID
PLATE-SCREEN -GRID
MA/Di V
VOLTS/DiV
200
10k
240
.2
o
GRID
PLATE
2
.2
Fig.
2-7.
Plate Current vs. Grid Voltage curves for the triode section
of a
6US.
voltage is desired. switch the PLATE - G RID
Control to P L ATE and read the peak voltage
directly from the screen.
A method of plotting a more conventional­
looking transfer characteristic is to connect the
plate to the
+
DC connection on the test panel
and adjust the
+
DC Control for the proper
voltage. Now if the PLATE-SCREEN-GRID
Control is turned to SCREEN the plate cur­
rent will be plotted. The advantages of this
connection are that the vertical lines are
not displayed and the plate voltage is
continuously variable and indicated by the
voltmeter.
Disadvantages are that the
m aximum current and voltage capability of the
+
DC connection are less than that of the normal
P connection and the continuous voltage applied
to the tube under test increases the average
plate diss ipation in the tube.
Grid Current
vs.
Grid Voltage
After displaying plate current versus grid
voltage curves the grid current vs. grid voltage
AA
O perating Instructions - Type 57 0
2 -7