Taylor 45C - Page 12

In
general
voltages nearest
to
normal
operating
conditions
can
be used, except for
power
valves
taking
over about
30
mA. anode
current
normally.
For these,
reduced voltages
should
be
used
to
avoid testing them
with
an
unnecessarily
high anode current.
The
grid
voltage should be that
recommended for
normal operation
(usually Class
A
amplifier
conditions).
If, however, lower anode and
screen
voltages are used,
the grid
bias
voltage
should
be
reduced in proportion to the reduction
in
anode voltage in the case
of a
triode,
or
the
screen voltage of. a tetrode
or
pentode.
Column 8
is
blank unless there is a top cap. If this is
a
grid
connection,
enter G
for
green,
if
anode
enter R
for
red. If
the electrode is not used
during
tests of another
section
in the
valve (e.g.,
the diode
of
a diode --triode) enter
B
for
black.
To
work
out
the
ABC
selector settings
in
Column
9,
refer
to the
wiring chart (Page
4).
There
are
10
circuits to whicn
me
pins of all valve Holders
are
connected
m me
manner
shown by
the
chart,
the
right-hand side
of
which also lists the
switch
connections
of the
ABC
selectors.
The letters C, A,
S, G,
refer to cathode, anode,
screen
grid and control
grid
respectively.
The top line on the chart, shows
that
selector A
connects
circuit
1
to
cathode
in
position
0,
grid in position
1,
cathode in
position
2,
anode
in
position
3
and so on.
Only
the
first
7
circuits
are controlled
by the selectors.
Circuit
8
is
permanently
connected
to
cathode
arid anode
respectively,
and circuits
S
and 10
carry
the
heater
supply.
EXAMPLE
1.
Triode type
30,
having the following
pin
connections
:
—
(UX4 base)
pin
1 filament
2 anode
3
grid
4
filament
The
circuit connections
for this
base
are given in the
fourth column from the
left.
Selector
A controls circuits
1 and
2,
i.e., pin
2 on circuit
2,
circuit 1
not being connected
on
this
holder.
Now
pin
2 is
anode,
so
the right-hand columns are
scanned for a
selector
position
giving anode on
circuit
2.
Positions
1 and 2
satisfy
this requirement,
no
account
being taken
of the circuit
1
connections
as
these are immaterial
in this instance. Selector
A
position 1
is therefore
chosen.
Similarly
selector
B
controls
pin
3
on
circuit
3,
circuit
4
not
being connected. This pin
is
grid,
so
position
2
is
chosen,
although
position 7
would
do as
well.
Selector
C controls
no pins
so it
is left
on
position 0.
The settings are therefore
120. The
filament
connections
on
pins
3 and 4
are made automatically as
circuits
9
and
10
are
permanently on the
filament
supply.
EXAMPLE
2. Indirectly
heated
pentode
type
6K7G having the
following pin connections
on an
international octal
base
:
—
pin
1 blank
(or shell
if
metal type)
2
heater
3 anode
4
screen
grid
5
suppressor
grid
6 blank
7
heater
8
cathode
top
cap
—
control
grid
The
108/1
holder
(No.
12)
must
be used,
as
the heaters
are on pins
2 and
7.
Selector
A
controls pins
5
and
4,
i.e.,
suppressor
and
screen respectively.
It should
therefore
be
on position
6
(cathode,
screen)
since
the
suppressor grid
is at
cathode potential. Selector
B
controls pins
1 and
3,
i.e.,
shell
and
anode.
Its
correct
position is therefore
No.
3
(cathode,
12