Eico 667 - MODEL 667 ADDENDUM - TRANSISTOR; Revised Transistor Test Procedure; Text Deletion Notice

MODEL
667 ADDENDUM
-
TRANSISTOR
(For Instruction
Manual)
An
Improved
procedure
has
been
developed
for transistor testing,
which
is
described
in
the
following revision
of steps
5
to
8
on
page
7 of
the
Instruction Manual.
No
transistor
chart
is
provided,
as
it
is
not required
when
using
the revised
test procedure.
With the great
number
of
transistors
now
available,
a transistor
handbook
would be needed,
in
any
case,
to determine
the
type (p-n-p or
n-p-n) and
basing of
all
the transistors
to
be
encountered.
Revised Steps 5
to
8,
Page 7 of the
INSTRUCTION MANUAL:
5.
Refer to
a
transistor
handbook for the type
(p-n-p
or
n-p-n)
and
basing of the
transistor to be
tested. Note
that only signal transistors can be tested
with
the
instrument
and
the criteria
described
below apply only
to
signal transistors (not
power
transistors).
*
6.
Insert the emitter
(E),
base
(B),
and
collector
(C)
lead
of the
transistor
In the corresponding
terminals
of
the transistor socket
located
immediately above
the
TRANSISTOR
TEST
selector,
7.
Turn
the
TRANSISTOR TEST
selector
from
"TUBE"
to
position
1
(first position
away
from
"TUBE")
on the
p-n-p
or
n-p-n
side depending
on
the
type
of transistor
under test.
The indication
on
the
meter
will
be
proportional to
the
collector
current
with emitter
grounded and
no base
signal.
On this test, transistors
in
good
condition should preferably
read
in
the
"Ico
GOOD"
area
between
0
and
40 on the
0
to 140 meter scale,
but
are acceptable
with readings
up
to
80
on
this
scale.
Reject
transistor that
reads
above
80 on this test.
8. Turn
the
TRANSISTOR TEST
selector to
position
2
(second
position
away
from
"TUBE"),
and
read
the
DC Beta (ratio
of
collector
current
to base
current).
The minimum acceptable
DC
Beta reading
depends
on the
Ico
reading
obtained
in
step
7.
The
higher
the
Ico
reading
(up
to
the maximum acceptable
limit of
80),
the
higher
the
minimum
acceptable
DC
Beta
reading
is,
in
direct
proportion*
Numerically,
the
minimum
acceptable
DC
Beta
reading
is
slightly
more
than
60% of the
Ico reading
on
the
0
to
140 meter
scale.
Examples:
If
the
Ico scale
reading
is
80,
the
minimum acceptable
DC Beta reading
is
50;
if
the
Ico
scale
reading
is
40,
the
minimum
acceptable
DC
Beta
reading
is
25.
Page
9 of
the
INSTRUCTION
MANUAL:
Delete
the
following material
from
the
text:
"In
some
cases,
the range of Beta
given In
the chart
has
been
taken
directly
from the
transistor
manufacturer's
specification;
in
other
cases
Beta
has
been
calculated
from
the
grounded
base
Alpha,
Alpha
ce,
according
to the
relationship:
Alpha ce
Beta
=
"
1
-Alpha ce
1