LOCATING COMPONENTS
POWER SUPPLY ISOLATION PROCEDURE
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Each regulated supply has num erous feed points to
external loads throughout the instrument. The po w er dis
tribution diagrams are used in conjunction with the
schematic diagram s to determ ine those loads th at can be
isolated by removing service jumpers and those
that cannot.
The power distribution and circuit board interconnec
tions diagrams are divided into circuit boards. Each p ow er
supply feed to a circuit board is indicated by the schematic
diagram num ber on which the voltage appears. The
schematic diagram ‘grid location of a service jum per or
com ponent is given adjacent to the component number on
the power distribution and circuit board interconnect
diagrams.
If a power supply comes up after lifting one of the m ain
jumpers from the pow er supply to isolate that supply, it is
very probable that a short exists in the circuitry on th at
supply line. By lifting jum pers farther dow n the line, the cir
cuit in which a short exists m ay be located.
AC Waveforms
warming |
Instrument m ust b e connected to the ac-power
source using a 1:1 isolation transformer. D o not con
ne c t th e test oscilloscope p rob e groun d lead to the
inverter circuit test points if the instrument is not iso
lated. A C -source voltage exists on reference points
TP 9 50 and T906 pin 5.
DC Voltages
Preregulator and Inverter voltages are referenced to
test point noted adjacent to the voltage. P ow er supply out
put voltag es are referenced to chassis ground.
Alw ays set the P O W ER switch to O FF before soldering
o r unsoldering service jum pers o r other com ponents and
before attempting to m easure com ponent resistance
values.
REV OEC 1986
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