HP 6268B Operating And Service Manual

Figure 5-7. Constant-Current Load Regulation Test Setup
POWER SUPPLY CASE OSCILLOSCOPE CASE
A. INACCURATE METHOD USING SINGLE ENDED SCOPE.
GROUND CURRENT I G PRODUCES 60 CYCLE DROP IN
NEGATIVE LEAD WHICH ADDS TO THE POWER SUPPLY
RIPPLE DISPLAYED ON SCOPE
POWER SUPPLY CASE OSCILLOSCOPE CASE
* LENGTH OF L E AO BETWEEN R s AND GROUNDED OUTPUT
TERMINAL of POWER SUPPLY MUST BE HELD TO ABSOLUTE
MINIMUM
B. RECOMMENDED METHOD USING A DIFEERENTIAL SCOPE WITH
FLOATING INPUT. GROUND CURRENT PATH IS BROKEN, COMMON
MODE REJECTION OF DIFFERENTIAL INPUT SCOPE IGNORES
DIFFERENCE IN GROUND POTENTIAL OF POWER SUPPLY AND
SCOPE, AND SHIELDED TWO-WIRE FURTHER REDUCES STRAY
PICKUP ON SCOPE LEADS.
Figure 5-8. Constant-Current Ripple and Noise Test Setup
supply. The presence of a 1 20Hz waveform on the oscillo¬
scope normally indicates a correct measurement method.
A waveshape having 60Hz as its fundamental component
usually indicates an incorrect measurement setup.
5-48 To check the ripple and noise, proceed as follows:
a. Connect oscilloscope or rms voltmeter as shown in
Figure 5-8A or 5-8B.
b. Rotate VOLTAGE controls fully clockwise.
c. Turn on supply and adjust CURRENT controls until
front panel ammeter reads exactly maximum rated output
current.
d. The observed ripple and noise should be less than:
6259B 250jljV rms
6260B 250/uV rms
6261B 250/iVrms
6268B 334/jV rms
6269B 250juV rms
549 TROUBLESHOOTING
5-50 Before attempting to troubleshoot this instrument,
ensure that the fault is with the instrument and not with
an associated circuit. The performance test (paragraphs
5-5 through 5-48) enables this to be determined without
removing the instrument from the cabinet.
5-51 A good understanding of the principles of opera¬
tion is a helpful aid in troubleshooting, and it is recom¬
mended that the reader review Section IV of the manual
before attempting to troubleshoot the unit in detail. Once
the principles of operation are understood, refer to the
overall troubleshooting procedures in paragraph 5-54 to
locate the symptom and probable cause.
5-52 The schematic diagram contains normal voltage
readings adjacent to some test points. (Test points are
identified by circled numbers.) The measurement conditions
are listed in the Schematic Notes. Consult the component
location diagrams in Section VII to determine the locations
of components and test points.
5-53 If a component is found to be defective, replace
it and re-conduct the performance test. When a component
is replaced, refer to the repair and replacement (paragraph
5-69) and adjustment and calibration (paragraph 5- 71)
sections of this manual.
5-54 OVERALL TROUBLESHOOTING
PROCEDURES
5-55 To locate the cause of trouble, follow steps 1, 2,
and 3 in sequence:
(1) Check for obvious troubles such as a defective
power cord, an input power failure, or a defective meter.
5-8

HP 6268B Specifications

General

Brand	HP
Model	6268B
Category	Power Supply
Language	English