136
6.
HIGH VACUUM, LOW—VOLTAGE TUBES
0-/0
-
/.75 A.
@
’
$C
.
,lll1
@ of,…
_
.
.
Barrou VIEW
_
OF ”A
;90v
——lz
FIG. 6—23.
Circuit for studying the characteristic curves of a screen-grid tube. J
subtracted from the plate and added to the screen-grid current, the
sum
(lt) of the plate and screen currents should be a constant,‘
equal to the total current which passes the control grid, i.e.—,
[; ”= [p + lag. Test this relationship.
EXPERIMENT 6—3
.
CONSTANTS OF VACUUM TUBES
‘
The circuits are shown in gures 6—6, 6—10 and 6—11. Particular care should be taken that the ground is connected as shown
in each case. .The oscillator O may be an electrically driven tun—
ing fork of Say 1000 cycles per second or a vacuum tube osc1llator
-
There should be a grounded electro—static shield between the
primary and secondary of its output transformer or there should
-
be a one—half megohm potentiometer aCross the secondary With
its sliding contact grounded. In gure6—6, n may be 10 ohmsfor‘
:
lov€7 mu tubes and one-ohm for high mu tubes. The potent1al
:
'
'
“
dr0p across 71 should not exceed 1 or 2 volts. A dial box maybe
_
used
By—pass condesers of low impedance should beused
around all“batteries and rectier-lter systems must be avo1dedr
Since
the batteries have capacity to the ground, they shouldbe
in such a manner=as to reduce this efÏect to as small avalue
screen—grid tubes, connections are to be madet@
p01ntaandfor PentOde
to the point & in gure
Con—
by introducing sa small
Phaseshlft Ingure
thismay be accomplished by meansof
asmallcapwtymparallelwmhrg Inthis circuit the res1stances
’”lf2andtsshouldbekeptas
In gureô—1î
6.
HIGH VACUUM, LOW—VOLTAGE TUBES
0-/0
-
/.75 A.
@
’
$C
.
,lll1
@ of,…
_
.
.
Barrou VIEW
_
OF ”A
;90v
——lz
FIG. 6—23.
Circuit for studying the characteristic curves of a screen-grid tube. J
subtracted from the plate and added to the screen-grid current, the
sum
(lt) of the plate and screen currents should be a constant,‘
equal to the total current which passes the control grid, i.e.—,
[; ”= [p + lag. Test this relationship.
EXPERIMENT 6—3
.
CONSTANTS OF VACUUM TUBES
‘
The circuits are shown in gures 6—6, 6—10 and 6—11. Particular care should be taken that the ground is connected as shown
in each case. .The oscillator O may be an electrically driven tun—
ing fork of Say 1000 cycles per second or a vacuum tube osc1llator
-
There should be a grounded electro—static shield between the
primary and secondary of its output transformer or there should
-
be a one—half megohm potentiometer aCross the secondary With
its sliding contact grounded. In gure6—6, n may be 10 ohmsfor‘
:
lov€7 mu tubes and one-ohm for high mu tubes. The potent1al
:
'
'
“
dr0p across 71 should not exceed 1 or 2 volts. A dial box maybe
_
used
By—pass condesers of low impedance should beused
around all“batteries and rectier-lter systems must be avo1dedr
Since
the batteries have capacity to the ground, they shouldbe
in such a manner=as to reduce this efÏect to as small avalue
screen—grid tubes, connections are to be madet@
p01ntaandfor PentOde
to the point & in gure
Con—
by introducing sa small
Phaseshlft Ingure
thismay be accomplished by meansof
asmallcapwtymparallelwmhrg Inthis circuit the res1stances
’”lf2andtsshouldbekeptas
In gureô—1î