HP BENCH Series User Manual

5-45 To check the transient recovery time, proceed
as follows:
a. Connect test setup shown in Figure 5-9.
b. Set METER SELECTION switch to rrA.
c. Turn on supply and adjust voltage controls
until front panel meter indicates exactly the maxi
mum rated output current.
d. Close the line switch on the repetitive
load switch setup.
e. Set the oscilloscope for internal sync and
lock on either the positive or negative load tran
sient spike.
f. Set the vertical input of the oscilloscope
for ac coupling so that small do level changes in
the output voltage of the power supply will not
cause the display to shift.
g. Adjust the vertical centering on the scope
so that the tail ends of the no load and full load
waveforms are symmetrically displaced about the
horizontal center line of the oscilloscope. This
center line now represents the nominal output volt
age defined in the specification.
h. Adjust the horizontal positioning control
so that the trace starts at a point coincident with a
major graticule division. This point is then repre
sentative of time zero.
i. Increase the sweep rate so that a single
transient spike can be examined in detail.
j. Adjust the sync controls separately for
the positive and negative going transients so that
not only the recovery waveshape but also as much
as possible of the rise time of the transient is
displayed.
\ t
\ I5MV
A _L
/ 50u
- A SOU
• y SECONDS
7
t
15 MV
'\ SECONDS
UNLOADING TRANSIENT LOADING TRANSIENT
Figure 5-10. Transient Recovery Time, Waveforms
k. Starting from the major graticule division
representative of time zero, count to the right
50 p.sec and vertically 10 mV. Recovery should be
within these tolerances as illustrated in Figure 5-10
5-46 TROUBLESHOOTING
5-47 Components within Hewlett-Packard power
supplies are conservatively operated to provide
maximum reliability. In spite of this, parts within
a supply may fail. Usually the instrument must be
immediately repaired with a minimum of "down
time" and a systematic approach as outlined in
succeeding paragraphs can greatly simplify and
speed up the repair.
5-48 TROUBLE ANALYSIS
5-49 General. Before attempting to trouble shoot
this instrument, ensure that the fault is with the
instrument and not with an associated circuit. The
performance test (Paragraph 5-13) enables this to
be determined without having to remove the instru
ment from the cabinet.
5-50 Once it is determined that the power supply
is at fault, check for obvious troubles such as open
fuse, a defective power cable, or an input power
failure. Next, remove the top and bottom covers as
described in Paragraph 5-3 and inspect for open
connections, charred components, etc. If the trouble
source cannot be detected by visual inspection,
follow the detailed procedure outlined in succeed
ing paragraphs. Once the defective component has
been located (by means of visual inspection or
trouble analysis) correct it and re-conduct the per
formance test. If a component is replaced, refer to
the repair and replacement and adjustment and cal
ibration paragraphs in this section.
5-51 A good understanding of the principles of op
eration is a helpful aid in troubleshooting, and it
is recommended that the reader review Section IV
of the manual before attempting to troubleshoot the
unit in detail. Once the principles of operation are
understood, logical application of this knowledge
used in conjunction with the normal voltage readings
shown on the schematic and the additional proce
dures given in the following paragraphs should suf
fice to isolate a fault to a component or small group
of components. The normal voltages shown on the
schematic are positioned adjacent to the applicable
test points (identified by encircled numbers on the
schematic and printed wiring boards).
5-52 Table 5-2 includes the symptoms and probable
causes of many possible troubles. If either high or
low output voltage is a symptom, there are two me
thods of isolating the fault. The first is a simpli
fied procedure that involves only measuring volt
ages; the second is a more thorough approach re
quiring that transistor stages be opened or shorted.
Both methods are described as follows:
5-8

HP BENCH Series Specifications

General

Brand	HP
Model	BENCH Series
Category	Power Supply
Language	English