IMSAI 8080 System
General assembly Notes
much as possible, and always touch the chip's container or
surface which it is touching before picking up the chip.
Also touch a surface or container before placing the chip
back in it. Touch a PC board before inserting the chip.
Touch the soldering iron to the work surface or to a small
piece of metal foil on the work surface before touching it
to the PC board for soldering. In general, make sure the
chip is not the path for any static discharge. Save MOS IC
insertion as the last steps in assembly to avoid unnecessary
exposure.
POLARITY
Many electronic components will not work if they are connected
backwards. Any component which it is important to insert one
way only will have a mark of some sort to indicate which way
is which. The board where they go will have some sort of
corresponding mark at each place, or an indication that all
such components go the same way as a marked "typical" one.
I.C.'s
All I.C.'s must be inserted with pin 1 in the correct location
to avoid damaging the I.C. Pin 1 is indicated on the chips
by several different marks. The most common is a rounded or
square notch in the center of the end near Pin 1. Another
common one is a slightly depressed or raised dot in the
corner of the chip next to Pin 1. One or both of these will
always be present to indicate Pin 1. Sometimes there are
other circular markings on the centerline of the chip, usually
towards one or both ends; these should be ignored. Often there
is some kind of Pin 1 mark on the bottom of the chip also.
(Note: Many I.C.'s have a code for date of manufacture which
is a 4 digit code. e.g. 7425 would indicate manufacture in
the 25th week of 1974. Do not confuse these with the device
number. The code will be alone, the device number will have
manufacturer-dependent suffixes and prefixes. e.g., SN7404N
is a 7404 type chip. On the PC board, some Pin 1 indication
will be found, such as a square pad, a dot, an arrow showing
Pin 1 direction with the note "typical" (indicating all chips
on the board face the same way), or similar mark.
24
To Next Page
Loading...
