IBM 1620 Manual page 6

TRANSIENT POWER LINE NOISE
The only pattern that can be associated with noise is its
lack of a pattern. If transient noise is suspected, the
Physical Planning Department should be alerted to the
situation. Listed below are some common symptoms
noted in the field:
1) High Iy intermittent failures
2) Failure defies any analysis by pattern
3) Failures occur mostly during the day (commonly
related to the start or end of a work day when
large numbers of equipment are being turned On
or Off).
4) Week end performance relatively trouble free.
Areas in the 1620 system most noise sensitive:
1) 1622 units tens ring
2) Binary triggers
3) Drift latches
Methods of determine noise:
1) Scope
a. Suspected line
b.
"J"
pins SMS Panels containing failures
c. AC input I ines at contactors
2) Indicator - A drift latch may be wired into circuit
and gated to indicate a transient pulse. One of the
test lamps (Tl or T2) on 1620 console could reflect
status of th is latch.
3) New Input - Run in temporary cable from building
serviceto 1620. This will give the CE a power
line free of building transients.
Methods of aggravating noise problems:
1) Determine other equipment on the 1620 line. Run a
program while throwing On/Off switchs on this
equipment, i.e., air-conditioning units, heaters,
other DP equipment, etc.
2) Separate AC and DC isolated ground from machine
frame.
Areas to investigate if noise problems are encountered
or suspec ted:
1) Is system on separate power line?
2) Does system have a good ground return to power
source (in most cases condu it ground is not satis-
factory)?
2.3