Fluke 2680A Service Manual page 175

Table 6-9. Relating Selftest Errors to Device Problems (cont)
Error Error Code
Code Description
10 Module 1
reference balance
test failed.
11 Module 1
overload
detection failed.
Suspect
Assembly
A3 A/D Background The A/D converters uses two very precise
Converter voltages for operation: +3.45 V dc and -3.45 V dc. These
PCA voltages are applied to resistor network A3Z1-1 and
A3Z1-3, with a balanced output at A3Z1-2. When the
two reference voltages are exact, the A3Z1-2 output is
nearly zero.
Failure This error occurs when the output of the
balance reference check at A3Z1-2 is not nearly zero.
Correction Troubleshoot the reference voltage circuitry
at A3U12 and A3U20 and related components. Check
the inputs and outputs of A3U12 and A3U20 and look for
an incorrect output, indicating a device failure.
A3 A/D Background This self-test is created by configuring for
Converter an ohms measurement, with treeing relays pulled in, but
PCA no channel relays are set. This creates an overload
measurement as the A/D converter tried to measure the
resistance of an open circuit.
Failure The error occurs when the A/D converter did
not detect an overload condition for measuring an open
circuit.
Correction There is a problem in the ohms conditioning
circuitry or possibly a problem in the A3U30 Stallion
device. The dc buffer might also be affected. Normally,
this error occurs in conjunction with other errors. If there
are not other errors, then the signal conditioning circuitry
is more likely at fault. Also, check the ohms current
source at A3U31 and related components. When the
precision 1 mA current sink is operating correctly, the
voltage across A3R128 is exactly 3.45 V dc and the
voltage across A3Z7-9 and A3Z7-11 is 1.00 V dc. If all
the voltages are correct, the A3U30 Stallion device
becomes more suspect.
Diagnostic Testing and Troubleshooting
Troubleshooting the Device
Error Code
Discussion
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