Control Data Corporation CYBER 180 810 Maintenance And Parts Manual page 47

CAUTION (CONTD)
• Damage to a module by reason of
backpanel short circuits (swapping a
good module into a faulty position
may result in damage).
• Damage to electrically adjacent
modules by a short in a 210-pak
(swapping a faulty module may cause
this).
-
An
understanding of the purpose of each module type and its relationship with
other modules is essential for selective isolation. For this purpose, the
Multilevel Block Diagram (MLBD) manual provides pak placement charts and
various levels of block diagrams.
VOLTAGE MARGIN TESTS
Voltage margin tests exercise the machine to find weak components and to
verify that the equipment operates over a range of voltage variations in a
controlled software environment. Weak components present the possibility of
future failure, or they may already be failing intermittently on normal
voltages. As a troubleshooting aid, voltage margin tests are used to locate
intermittent problems by causing them to occur at a-steady rate. This allows
the use of scoping or selective isolation techniques while the problem is
intensified under the applied marginal voltages.
TIMING MARGIN TESTS
Timing margins provide the means for locating slow switching circuits, weak
logic voltages, and other problems which can cause changes in the basic timing
of the machine. The clock period and the pulse width (frequency margins) are
varied for these procedures. Refer to the appropriate CAMS procedures to
adjust and run clock frequency and pulse width margins on system components.
SHOTGUNNING
CAUTION
Exercise care when using this technique
on 210-pak modules for the reasons
stated under Selective Isolation.
Shotgunning is the process of swapping or changing a large number of modules
in an attempt to locate a problem. Shotgunning should be used only when all
other techniques have failed.
60469500 A
4-13