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SECTION V
MAINTENANCE
5-1
INTRODUCTION
5-2
Upon receipt of the power supply, the per-
formance check (Paragraph 5-10) should
be
made.
This check is suitable for incoming inspection.
If
a fault is detected in the power supply while making
the performance check or during normal operation.
proceed to the troubleshooting procedures (Para-
graph S-41). After troubleshooting and repair (Para-
graph S-46), perform any necessary adjustments
and calibrations (Paragraph 5-48). Before returning
the power supply to normal operation, repeat the
performance check to ensure that the fault has been
properly corrected and that no other faults exist.
Before doing any maintenance checks, tum
on
pow-
er supply, allow a half-hourwarm-up, and read the
'general information regarding measurement tech-
niques (Paragraph 5-3).
5-3
GENERAL MEASUREMENT TECHNIQUES
5-4
The measuring device must-be connected
across the sensing leads of the supply or as close
to the output terminals as possible when measuring
the output impedance, transient response, regula-
tion. or ripple of the power supply in order to
achieve valid measurements. A measurement made
across the load includes the impedance
of
the leads
to the load and such lead lengths can easily have
an impedance severa
1
orders of magnitude greater
than the supply impedance. thus invalidating the
measurement.
S-5
The monitoring device should
be
connected
to the
+S
and
-s
terminals (see Fic;ure
3-2) or
as
shown in Figure S-1. The performance characteris-
tics should never
be
measured on the front terminals
if
the load is connected across the rear terminals.
Note that when measurements are made at the front
terminals. the monitoring leads are connected at A,
not B, as shown in Figure S-1. Failure to connect
the measuring device atA willresuitin a measure-
ment that includes the rest.stance
of
the leads be-
tween the output terminals and the point of connec-
tion.
S-6
For output current measurements, the current
sampling resistor should be a four-terminal rests-
LOAD LEAD
Figure 5-1. Front Panel Terminal Connections
tor. The four terminals are connected as shown in
Figure 5-2. In addition, the resistor should
be
of
the low noise, low temperature coefficient Oess
than 30ppmfOC) type and should
be
used at no
more than
5% of
its rated power so that its temper-
ature rise
will be
minimized.
CURRENT SAMPLING
TERMINALS
TO UNGROUNDED
TO GROUNDED
TERMINAL OF
+-W.--~W.."'0---1•
TERMINAL OF
POWER SUPPLY
POWER SUPPLY
Figure 5-2. Output Current Measurement Technique
5-7
When using an oscilloscope, ground one ter-
minal of the power supply and then ground the case
of
the oscilloscope to this same point. Make cer-
tain that the case is not also grounded by some
other means (Power line).
Connect both oscillo-
. scope input leads to
the
power supply ground termi-
nal and check that the oscilloscope is not exhibi-
ting a ripple or transient due
to
ground loops, pick-
up, or other means.
s-e
TEST EQUIPMENT REQUIRED
5-1
S-9
Table 5-1 lists the test equipment required to
perform the various procedures described in this
Section .
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