Agilent Technologies E3630A service manual Stability Drift, Initial Troubleshooting Procedure

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.

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.

		Table A-2. Miscellaneous Troubles
SYMPTOM		CHECK - PROBABLE CAUSE
High ripple	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.
Will not current limit	Check for open OR-gate diodes (CR7, CR11, CR18) or defective current limit amplifier
	(U2, U6, U8).
Poor load and line regulation	a.	Check bias and reference voltages, Table A-4.
	b.	Check main rectifiers and filters for opens.
Oscillation or poor transient	a.	High frequency oscillations (above 50 kHz) can be caused by an open C11, C20, or C25.
response time	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.
Transient voltage overshoot at	a.	Overshoot only in the -20V supply can be caused by a shorted Q3.
turn-on or turn-off	b.	Overshoot in all three supply outputs can be caused by an open Q2 or a shorted Q6.
Excessive heat	a.	Check preregulator control circuit. Refer to Table A-8 and Table A-9.
	b.	Check CR27, CR28, CR31, CR32 for short.
Output Voltage clamped	Check preregulator control circuit. Refer to Table A-8 and Table A-9.
above 10V for ± 20V output

A-7