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(nominally 1. 6 ohms) while the X-drive line resistance is a function of word length only
(nominally 2 ohms for a 16-bit memory).
c.
Measure continuity by referring to the simplified selection diagram, Figure
2-28 (Chapter II of this volume).
For example, to check the continuity of drive line Y 1, put
one ohmmeter probe on the corresponding sink output (emitter output of transistor Q3) and
the other ohmmeter probe on the proper switch output (collector of transistor Q2).
A low
resistance (one forward diode drop plus a drive line resistance given in the preceding para-
graph} indicates continuity for both diodes and the drive line.
It may be necessary to re-
verse the probes to obtain the correct polarity to forward-bias the selection diodes.
The
continuity of the current path for the opposite drive polarity should be similarly checked by
moving the probe from the collector of Q2 to the collector of Q 1 and reversing the polarity.
A high resistance reading in both drive current polarity paths indicates an open drive winding
or drive bus.
If a drive bus is open, the other drive lines connected to the same bus will
also have a high resistance reading.
A high resistance reading in only one of the read or
write current paths indicates an open F-08 Flat Pack diode.
3-8
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