Tequipment Agilent E361 Serie Manual De Funcionamiento Y Servicio página 24

Ammeter and CC Set Calibration
To calibrate ammeter and CC set, proceed as follows:
a. Connect test setup on Figure A-9.
b. Turn VOLTAGE and CURRENT control fully clock-
wise.
c. Turn on the supply and to calibrate ammeter adjust
R5 on the display board until front panel AMPS dis-
play reads exactly DVM value divided by Rs.
d. To calibrate CC Set adjust R69 on the main board
until front panel AMPS display reads exactly DVM
value divided by Rs while depressing OVP/CC Set
switch.
Voltmeter and OVP Set Calibration
To calibrate voltmeter and OVP set, proceed as follows:
a. Disconnect Rs from test setup on Figure A-9 and
connect DVM across output terminal of the supply.
b. Turn on the supply.
c. To calibrate voltmeter for E3614A, adjust R16 on the
display board until front panel VOLTS display reads
exactly DVM value. To calibrate voltmeter for
E3615A, E3616A and E3617A set the output voltage
below 18V (ex, 15V), and adjust R16 on the display
board until front panel VOLTS display reads exactly
DVM value. Next, set the output voltage above 20V
(ex, 21V) and adjust R17 on the display board until
front panel VOLTS display reads exactly DVM value.
d. To calibrate OVP Set, turn down the OVP Adjust
screwdriver control on the front panel slowly until the
OVP circuit trips. Record the output voltage when the
OVP trip occurs. Then adjust R97 on the main board
until front panel VOLTS display reads exactly OVP
trip voltage while depressing OVP/CC Set switch.
TROUBLESHOOTING
Before attempting to troubleshoot the power supply, ensure
that the fault is with the supply and not with an associated cir-
cuit. The performance test enables this to be determined
without having to remove the covers from the supply.
The applicable test points are identified by encircled
numbers on the schematic diagrams at the rear of the
manual, Figure A-10, Figure A-11, Figure A-12, and
Figure 13.
A good understanding of the principles of operation is a help-
ful aid in troubleshooting, and it is recommended that princi-
ples of operation in this manual be reviewed before
attempting to troubleshoot the supply. Once the principles of
operation are understood, refer to the overall troubleshooting
procedures paragraph to locate the symptom and probable
cause.
Once the defective component has been located (by means
of visual inspection or trouble analysis) replace it and recon-
duct the performance test. After a component is replaced,
perform the meter calibration.
Overall Troubleshooting Procedure
To locate the cause of trouble follow steps 1, 2, and 3 in
sequence. Before attempting overall troubleshooting, ensure
that the rear-panel switches M/S 1 and M/S 2 be set to MAS-
TER position and CV, CC, and SENSE to LOCAL position.
1. Check that input power is available, and check the
power cord and rear panel line fuse. When replacing
line fuse, be certain to select fuse of proper rating for
line voltage being used.
2. In almost all cases, the trouble source can be caused
by the dc bias or reference voltages; thus, it is a good
practice to check voltages in Table A-2 before pro-
ceeding with step 3.
3. Disconnect the load and examine Table A-3 to deter-
mine your symptom, then check the probable cause.
Reference and Bias Circuit
a. Make an ohmmeter check to be certain that neither
the positive and negative output terminal is grounded.
b. Turn front panel VOLTAGE and CURRENT controls
fully clockwise.
c. Turn on power supply (no load connected).
d. Proceed as instructed in Table A-2.
Regulating Loop Troubles
If the voltages in Table A-2 have been checked to eliminate
the reference and bias circuits as a source of trouble; the mal-
function is caused by either the series regulator or preregula-
tor feedback loop. Because the interaction between these two
loops makes logical troubleshooting difficult, the following
steps help you to locate the source of troubles in these two
feedback loops. Once the trouble has been located to one of
the feedback loops, the operation of either loop can be ana-
lyzed independently. This method should be followed when-
ever a low output voltage condition exists. Notice that
troubleshooting can proceed directly as described in Table A-
4 whenever a high output voltage condition exists.
1. Turn on the power supply with full load connected
and increase output voltage by turning up the front
panel voltage control. The output voltage is clamped
and CV indicator is turned off at some output voltage
(below full rated output voltage). If this is the case,
the series regulator feedback loop is operating
normally and the trouble condition is probably due to
a defect in the preregulator feedback loop (refer to
Table A-6). If the output voltage remains in low stage,
and varying the front panel voltage control has little or
no effect, then the trouble is probably in the series
regulator feedback loop. Refer to Table A-5.
2. Measure the voltage between TP2 and TP1 (shown
on the schematic diagram at the rear of the manual)
with full load with oscilloscope while increasing the
output voltage from 0 to full rated voltage. The volt-
age measured has step changes three times during 0
to full output voltage swing. If this is the case, prereg-
ulator feedback loop is operating normally. If this is
not the case, the trouble is probably in the preregula-
tor feedback loop. Refer to Table A-6.
A-8