Self-Test Troubleshooting - HP 3456A Operating And Service Manual

Model 3456A
k. Test # 1 1 . The 500 nA current source is applied to
the top of the 10 M ohm resistor of the 100: 1 Divider.
The voltage across the 10 M ohm resistor is applied to
the Input Amplifier with the amplifier in the X2 gain
configuration.
\.
Test #12. The 5 microAmp current source is ap­
plied to the AC Converter. The converter's output is
connected to the input Amplifier with the amplifier in
the X2 gain configuration.
8·334. Self·Test Troubleshooting.
8-335. The following paragraphs have troubleshoot in­
formation for the 3456A's Self-Test mode.
n.
8-336. Test I f this test fails, try replacing the RAMs
in the Outguard Logic (A4U 10, U 1 1 shown on
Schematic 9). If that does not help, go to Service Group
A for troubleshooting.
8·337. Test 112. If this test fails, try replacing the
Outguard Microprocessor (A4U I 5 shown on Schematic
9). If that does not help, go to Service Group A for
troubleshooting.
This test fails if either the Inguard or
8-338. Test 113.
Outguard Isolation Logic is inoperative. Since either
Isolation Logic can cause the test to fail, the faulty cir­
cuitry needs to be determined. A procedure is in Service
Group A, Paragraph 8-A-34 and Service Group B,
Paragraph 8-B-6.
I f this test fails, the instrument
8-339. Test 114.
malfunction can be in the Inguard Logic, AID Cir­
cuitry. and DCV Analog Circuitry (Input Switching and
Input Amplifier). This test quite often fails when an
Overload condition (OL) is dislayed (in all function and
ranges). A procedure to determine the faulty area is in
Service Group B, Paragraph 8-B-8 or Service Group C,
Paragraph 8-C-IO.
8-340. Test 115 and 116. If any of these tests fail, the
malfunction is most likely in the Input Amplifier's feed­
back circuitry. This is because these tests are similar to
Test #4 with the amplifier in a different gain configura­
tion (XIO for Test #5 and XIOO for Test #6). Try replac­
ing A2OQ307 if Test #5 fails or Q309, i f Test #6 fails (see
Schematic 3). I f the test(s) still fail. go to Service Group
C for troubleshooting.
&-341. Test ll7. I f this test fails, the failure can be in the
AID Converter or Inguard Logic. Go to Service Group
B for troubleshooting.
If any of these tests fail. the
8-342. Test 11& or 119.
failure is most likely in the AC Converter. Before
troubleshooting the converter, perform the ACV Ad­
justment first (in Section V of this manual). I f the test
still fails. go to Service Group E for troubleshooting.
8-343. Test 1110 or 1111. I f these tests fail, the failure
can be in the Ohms Converter, Input Amplifier, or In­
put Switching. To determine the circuitry. make sure the
3456A is good on the 1 00 V and 1000 V Ranges in the
DCV Function. I f the ranges are faulty, go to Service
Group C for troubleshooting. I f the ranges are good,
the Ohms Function most likely at fault (the 1 0 M ohm
Range and higher are inoperative). Go to Service Group
D for troubleshooting.
I f this test fails. the failure can be in
8-344. Test 1112.
the Ohms Converter or AC Converter. To determine the
circuitry, set the 3456A to the I M ohm Range in the
0
Ohms Function. If the function is inoperative, go to
Service Group for troubleshooting. If the function is
good, the AC Converter is at fault. Go to Service Group
E for troubleshooting.
Service
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