CIRCUIT
DESCRIPTION
ALL
CIRCUITS described in the electrical principles of
the
Type 82 Card Sorting Machine will refer to wiring
diagram
301701-D (Figure
55).
Those circuits
ex-
plained will
be
the circuits incorporated in a 115 volt
AC, single phase machine
since
this
is
the type of
machine most prominently
in
use
in the
field.
Circuits
for machines using a power supply other than
115
volt
AC, single phase will
be
found to be very similar in
layout except
for
the addition or subtraction of various
resistors, filter capacitors, or a transformer
in the
ma-
chine power supply. These discrepancies in machine
wiring are noted
in
sections 3,
4,
5 and 6 of the wiring
diagram.
Direct current
is
required
for
the operation of all
machine circuits with the exception of the motor
cir-
cuits and the tube heater circuits. Where the source
voltage
is
DC, there
is
no problem except for the
use
of extra resistors where the DC rating
is
230 volts.
Where the source voltage
is
AC however, selenium
rectifiers are employed to convert the
AC
to
DC.
NOTE:
The machine frame should
be
grounded.
It
may
be
ungrounded at the customer's option; however,
except for
230 volt DC machines, which must have
the frame grounded at all
times.
No point which can
be
touched
by
operating personnel can
be
hot when
the switch
is
on and the frame grounded.
Selenium Rectifiers
The selenium dry
disc
rectifier
consists
of an electrode
made of a steel or aluminum
disc,
nickel plated or
otherwise coated to prevent rust. On one
side
of the
disc
is
deposited
a thin coating of selenium, over which
is
sprayed a metallic conductive coating of low tem-
perature alloy. Where the selenium and the low
tem-
perature alloy meet, a barrier layer
is
formed
by
a
special
process.
It
is
this barrier layer which permits
electron
flow
from the coated electrode to the steel
electrode but restricts electron
flow
in the reverse
direction.
There are two
types
of selenium
discs
in
use
by
IBM
at present. In one type, each
disc
will
effeccively
block
18 volts
in
the reverse direction; in the other type, each
disc will effectively block 26 volts in. the reverse
di-
reotion. There
is
no visual difference
in
the appearance
of each type.
22
The connection of selenium rectifiers in an AC
cir-
cuit permits current
to
flow
in
one direction only, even
though the
AC
voltage reverses each half
cycle;
thus
converting alternating current to pulsating direct
cur-
rent. However, because of the limitation in reverse
voltage which each
disc
can effectively block, several
discs
must
be
connected in
series
with each other in
order to properly rectify a normal source voltage of
115
volts AC which has a peak inverse voltage of
ap-
proximately 150 volts. Full wave bridge rectifier cir-
cuits with filter capacitors and bleeder resistors are
used
most commonly in the power supplies of IBM
machines.
The rectifier output voltage should be between
135
and
145
volts at the
specified
input voltage ( 115,
200, or 230 volts), with the machine stopped and the
sort magnet continuously energized.
Duo Relays
Duo relays used
in
IBM machines are constructed
with various arrangements of contact points
in
their
makeup. For
this reason, the contacts
are
given a def-
finite nomenclature
to
differentiate between them on
the relay and on the wiring diagram. Figure
21
shows
AU
~
~"/C
BU
BL
AL
Armature
,-_-Coli
Fj~ure
21.
Duo
Relay
Nomenclature
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