Agilent Technologies E3620A Manual De Funcionamiento Y Servicio página 82

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 Tests" paragraph.
Before applying power to the supply, make certain
that its line voltage selector switch (S1) 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.
SYMPTOM
High ripple
Will not current limit
Poor load and line regulation
Oscillation or poor transient
response time
Excessive heat
Output Voltage clamped for
each output
STEP ACTION
1 Check output voltage of V1
and V2 supplies.
Table A-2. Miscellaneous Troubles
a. Check operating setup for ground loops.
b. Check main rectifiers(CR2, CR3, CR4) for open.
c. Supply may be operating in current limit mode. Check current limit adjustment, steps (l) thru (n)
on page A-4.
Check for open OR-gate diodes (CR9, CR21) or defective current limit amplifiers (U10, U19).
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 C13 or C35.
b. A defective output capacitor (C10 or C29) can cause oscillations in one of many frequency
ranges.
c. Oscillation only in the current limiting mode can be caused by an open C34 or C12.
a. Check preregulator control circuit. Refer to Table A-7 and Table A-8.
b. Check Q3, Q4 and Q5 for short.
Check preregulator control circuit. Refer to Table A-7 and Table A-8.
Table A-3. Initial Troubleshooting Procedure
RESPONSE
a. Zero volts
b. Output voltage lower or
higher than rating
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 amp fuse and
standard and Option OE9, use a slow-blow 2 amp fuse.
CHECK - PROBABLE CAUSE
a. Check ac line fuse (F1). If blown, proceed to "Open
Fuse Troubleshooting" paragraph. If not blown, check
bias and reference voltages (Table A-4).
b. Check bias and reference voltages (Table A-4).
A-7
NEXT ACTION