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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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