Electrical
Test lnstruments
MAC-20 Retrofit Package
Section ll
-
Detailed
Description
MAC-20 lnternal
Parts
INPUT CONNECTOR:
This
connector, located
on the lower rear corner
of the MAC-20,
provides
120
VAC control
power,
and connects
to
the
air core CT
(current
sensor),
and
initiate
circuitry
of the test set. The wiring
of this connector is
essentially compatible with
that of
the EIL Accu-Amp,
and ib designed
to
facilitate
removal of
the
MAC-20
for
service or shipment.
ANALOG INTERFACE
PC BOARD:
This PC
board, located near the input
connector,
contains all
of the MAC-20
analog circuitry. lt
has two
potentiometers
for
zero offset,
and one
potentiometer
for
gain.
lt also
provides
unregulated 10 VDC
for the mother
board
MICROPROCESSOR
MOTHER
BOARD: This PC board, located
adjacent
to the
analog
interface,
contains
a regulated
power
supply and support circuitry
for the
microprocessor
core module,
and
programmable
peripheral
interfaces for
the analog
board and keyboard / display
board. lt also supplies regulated
5 VDC for
the
keyboard
/
display board.
MICROPROCESSOR CORE
MODULE: This
small
PC
board, manufactured
by ZWorld
Engineering
and called the SmartCore, contains
a Zilog Z-180 microprocessor,
crystal
controlled clock, support
circuitry, static MM, and socketed
program
EPROM. lf
changes to firmware are required,
the EPROM must be replaced.
THIS SHOULD BE
DONE ONLY BY PERSONNEL EXPERIENCED
IN HANDLING
STATIC SENSITIVE
ELECTRONIC COMPONENTS.
KEYBOARD / DISPLAY BOARD: This large PC
board, located on the front
panel,
contains both LED
displays and all keys used in the MAC-20. lt
also contains an audible
beeper, and circuitry
for
the continuity light, contacts
sensing, and output initiation. lt
connects to the motherboard with a 26
pin
ribbon
cable and a
two
conductor
power
cable.
Electrical
Test lnstruments,
lnc.
Page ll-7
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