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SMS Modules - Physical Characteristics
A Little History
IBM created and used a family of SMS printed circuit cards in IBM computers and peripherals manufactured in an about 8 year period from the late 1950s and early 1960s. This was the card format that replaced the previous vacuum tube circuits. Many/most? post vacuum tube era IBM computers used this card format, including 7090, 7094, 1620, 1401, ...
These cards were all the same size (with a double width card allowed) and used "discrete" components, resistors, capacitors, transistors, diodes, ...
The next IBM format was for a "hybrid" circuit family for the IBM 360 series computers which started shipping in 1965.
Purpose of this Page
Provide some physical information to aid thinking and planning
People at CHM wish to inventory, repair, use, ... these cards in at least two restored IBM computers, the IBM 1620 and the IBM 1401.
The SMS cards used in the IBM 1620 use a different circuit philosophy (not many diodes) from the SMS cards used in the IBM 1401 (many diodes). (We have not gotten into the SMS cards used in the IBM 729 tape drives.)
Even different revisions and features of the IBM 1401 use different SMS cards. As an example, the printer hammer drivers used in the Visible Storage 1401 have a different name ("AEC") and circuit layout, but interchangeable with, the printer hammer driver cards in the restored 1401 ("AEN").
SMS Card Physical Characteristics
which affect possibilities for marking and tagging.
Hammer driver cards Hammer driver cards represent rather "well stuffed" SMS cards. 4.5 inches long, components part 3-5/8 inches, plug part 5/8 inches 2-5/8 inches wide.
Note there is very little room for the card type, and number indicating other manufacturing information. Note that there is no unique number identifying and individual SMS card. Card type "AEC" near the lower left corner of the top card, "AEN" on the lower card.
Inventory control & identification
Our ex-Customer Engineers indicate the a card returned from a repair depot had a black mark on the opposite edge from the socket. Note that there is a slightly larger hole hear that edge, which seems to be on all SMS cards. (This hole was possibly used in manufacture?)
"We" are somewhat sympathetic to the idea of identifying each card for repair history, and possibly other reasons.
"We" don't think tagging the cards with the string & cardboard type tag is a good idea as the loose tag is at high risk to interfere with the forced air circulation.
As of May 19, 2006, "we" have not agreed on a scheme to uniquely identify each SMS card.
Page created May 19, 2006