This page describes the IBM SMS card "YJA", and is part of the SMS card database.

Function of the card:
Alloy-Resistor Card, 3 Watt [MARS Resistor Load Matrix]
Alloy-resistor card, 3 watt

Hex Pullup +12V 40.2ohm 3W

Germanium alloy transistors were an early type of transistor, faster than the earlier grown-junction transistors.

Part number: 370788

PCB number: 492345

Used in: IBM 1620


R: Load. Provides proper terminating impedance or optimum coupling of one circuit to another at the correct operating voltage level.


A spare
B R1
C R2
D R3
E R4
F R5
G R6
H spare
K spare
L spare
M spare
N spare
P spare
Q +12V
R spare
References: IBM 1620 Instructional System Diagrams, p471
Coslet data

This page created by Ken Shirriff on Wed Sep 15 18:15:10 2021.

The information on these pages comes from a variety of sources, especially old IBM documents on, as well as information from the IBM 1401 restoration team, especially Tim Coslet's SMS data and Jim Hunt's data. Much of this information was obtained through OCR, so don't expect complete accuracy. These pages are not associated with IBM in any way.