Tektronix 570, Manual

Page: 4 / 134

570
Bias voltoge applied to the grid of the tube under test
is impressed in a series of steps to produce the number of
curves desired in the display. The voltage difference be­
tween steps is selected by
a
seven-position switch. Cali­
brated switch positions ore: 0.1, 0.2, 0.5, 1, 2, 5, ond
10 volts/step, accurate within 3"10. Up to 1 50 mo peak
grid current is available. A variable control is provided
to adiust the starting point to
a
positive voltage, zero, or
a negative voltage. Pressing the ZERO BIAS push button
causes the display of the zero-bias curve only, to use as
a
reference in adiusting the starting point. As many as
eight positive-bios curves can be included in the display.
PIATE.SWEEP GENERATOR
An eleven-position switch selects the desired series­
load resistance for the plate circuit of the tube under test.
Series-load values ore:
300
ohms,
1
k,
2
k,
5
k,
10
k,
20 k, 50 k, 100 k, 200 k, 500 k, and 1 megohm. Power­
handling capacity of
all
load resistors is sufficient to dis­
sipate the maximum power available in the plate circuit.
The peak voltage applied to the plate through the
series-load resistance is selected by on eight-position
switch. Peak voltages are: 5, 10, 20, 50, 100, 200, 300,
and 500 volts.
OPERATING VOLT AGES
Heater voltage is available in
17
fixed steps:
1.2 5,
1.4, 2.0, 2. 3 5, 2.5, 3.15, 4.2, 4.7, 5.0, 6.3, 7.5, 12.6,
18.9, 25, 35, 50,
and
117
volts ac. A control permits
adiusting the selected heater voltage approximately
±
20 %
for simulating the effects of low or high line
voltage. The variable control provides sufficient spread
between steps to supply the proper heater voltage for
practically
011 receiving-type vacuum tubes. Maltimum
power available from the heater transformer is
30
watts.
Positive dc voltage is available in five calibrated steps:
20, 50, 100, 200, and 300 volts, accurate within 3 %.
The positive voltage is also continuously variable from
appro)timately
10 to 300 v. Up to 50 ma steady current
is supplied. An adequate reserve is available for higher
peak currents.
Negative de voltage is available, continuously vari­
able from 0 to - 100 v. The negative dc supply is cap­
able of delivering up to 1 watt.
ADAPTER PLATES
Eight quick-changing adapter plates are furnished
with the Type 570 - 2 with octal sockets, 2 with nine­
pin miniature sockets, 2 with seven-pin miniature sockets,
and 2 with pilot holes only. Plate receptacle holds any
two adopter plates at the same time. Small banana jacks
connect
10 each socket terminal thus making it possi­
ble to patch any tube element to any voltage supplied
by the instrument.
Other adopter plates ore available os optional ac­
cessories.
VOLTMETER
The built-in voltmeter indicates the positive and nega­
tive operating voltages in seven ranges:
0
to
7, 14, 3 5,
70, 140, 350, 700 volts. The voltmeter con be switched
to show the percent of heater voltage indicated by the
heater-voltage selector switch.
OTHER FEATURES
Tube·Socket Switching-The
TEST POSITION switch
in the center of the front panel is used to switch in either
of two vacuum tubes during comparison tests. It has an
OFF position for changing tubes and for establishing 0
reference trace on the screen. Control-grid potential
drops to
-150
v in the off position.
Fig. I-Plole current planed againsl plate volt­
age far one triade se
c
t i o n of a 12AU7. 'Iale
load i.
S k,
peak plate-supply voltage is
SOO
v.
Grid voltage is
c
h a n g ed 5 v b e t we e
n
(urves, f r o
m
-35 v la zero. Vertical sensilivity is
S m
a
/
d
i
v
,
horizonlol sensitivity 50 v
/
div. Col ibraled (antral.
permit
accurate c
u
rr e n t and voltage readings
direc t l y from tne screen.
Fig. 2.-Some
t
r
i a d e
section
of
12AU7
with only Fig. 3--Screen c",.ent plaited against plale valt-
20-v peak plate supply and sensitivities increased age wilh po
s
i
t
i ve grid bias an
0
6A05.
plate
fa
0.2 ma/
di v
vertical and 2
v/div hori�antal. load is 300 o h
ms
.
peak plate voltage is 100 v,
Grid valla"e is
c
h a n g ed
2
v between
curve..
screen-grid voltage is I 00 v, with grid voltage
from -'4
•
la
:te
r a. This is essentially a 25·times c h a n gi
n
g
2
vlitep
f
r o
m + 16
v 10
b
el ow zero.
magnification
of
t
h
e
lower left portion of
Fig.
1.
Vertic:al
scale
is
10
m
o
/
di
v
,
horizontal scale is 10
vi
showing Ihe aperaling chara,teri,tic.
ot
J
a w plate- div.
.upply v o ltag e
.