Agilent Technologies E3630A Manual De Funcionamiento Y Servicio página 91

Stability (Drift)
Definition: The change in output voltage (dc to 20 Hz) for the
first 8 hours following a 30-minute warm-up period with con-
stant input line voltage, constant load resistance and constant
ambient temperature.
To measure the stability:
a. Connect the test equipment across the output of the
+20V supply as shown in Figure A-6.
b. Operate the electronic load in constant current mode and
set its current to the full rated value of power supply.
c. Turn on the supply.
d. Turn up output voltage to the full rated value as read on
the digital voltmeter.
e. After a 30-minute warm-up, note the voltage on DVM.
f. The output voltage reading should deviate less than 0.1%
plus 5 mV from the reading obtained in step e over a
period of 8 hours.
g. Repeat for the remaining supply outputs.
TROUBLESHOOTING
Before attempting to troubleshoot the power supply, ensure
that the fault is with the supply and not with an associated
piece of equipment. You can determine this without removing
the covers from the power supply by using the appropriate
portions of the "Performance Test" paragraph.
SYMPTOM
High ripple
Will not current limit
Poor load and line regulation
Oscillation or poor transient
response time
Transient voltage overshoot at
turn-on or turn-off
Excessive heat
Output Voltage clamped
above 10V for ± 20V output
Figure A-8. Load Transient Response Time Waveform
Table A-2. Miscellaneous Troubles
a. Check operating setup for ground loops.
b. Check main rectifiers(CR1, CR25, CR26) for open.
c. Supply may be operating in current limit mode. Check current limit adjustment, steps (k)
thru (r) on page A-5.
Check for open OR-gate diodes (CR7, CR11, CR18) or defective current limit amplifier
(U2, U6, U8).
a. Check bias and reference voltages, Table A-4.
b. Check main rectifiers and filters for opens.
a. High frequency oscillations (above 50 kHz) can be caused by an open C11, C20, or C25.
b. A defective output capacitor (C2, C3, or C4) can cause oscillations in one of many frequency
ranges.
c. Oscillation only in the current limiting mode can be caused by an open C12, C19, or C24.
a. Overshoot only in the -20V supply can be caused by a shorted Q3.
b. Overshoot in all three supply outputs can be caused by an open Q2 or a shorted Q6.
a. Check preregulator control circuit. Refer to Table A-8 and Table A-9.
b. Check CR27, CR28, CR31, CR32 for short.
Check preregulator control circuit. Refer to Table A-8 and Table A-9.
Before applying power to the supply, make certain
that its line voltage selector switch (S2) is set for the
line voltage to be used.
Initial Troubleshooting Procedure
If a malfunction is found, follow the steps below:
a. Disconnect input power from the supply and remove all
loads from the output.
b. Table A-2 lists the symptoms and probable causes of sev-
eral possible troubles. If the symptoms is one of those
listed, make the recommended checks.
c. If none of the symptoms of Table A-2 apply, proceed to
Table A-3. This table provides an initial troubleshooting
procedure that also directs you to the more detailed pro-
cedures which follow it.
The numbered test points referred to in the troubleshooting
procedures are identified on the circuit schematic at the rear
of the manual.
Open Fuse Troubleshooting
Although transients or fatigue can cause a fuse to blow, it is a
good idea to inspect the unit for obvious shorts such as dam-
aged wiring, charred components, or extraneous metal parts
or wire clippings in contact with circuit board conductors
before replacing the fuse. The rating of the correct replace-
ment fuse depends on the line voltage option of the instru-
ment: for Option OE3, use a slow-blow 1.0-amp fuse and
standard and Option OE9, use a slow-blow 1.6-amp fuse.
CHECK - PROBABLE CAUSE
A-7