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Troubleshooting
Interpreting Diagnostic Fault Codes
5
5-23
assembly. The resulting 0.2V across the 10 kΩ portion of Z5 is connected to the +input
of the differential amplifier. The output of the differential amplifier is routed to the adc
circuit on the DAC assembly, via the RCL line, and measured for 0V ±3% ±15 mV. A
failure indicates the calibration of the 100Ω resistance on the Ohms Main assembly
(A10) is probably at fault.
3341 A9/A10: 190 Ohm Cal Diag Fault
The 2/5/10V SOURCE circuit is set for 2V and connected across the 1.9 kΩ string on the
Ohms Main assembly. The resulting 0.2V across the 190Ω portion is connected to the -
input of the Differential Amplifier on the Ohms Cal assembly. The output of the DAC
assembly is set to 2V and connected across the 100 kΩ resistance in Z5 on the Ohms Cal
assembly. The resulting 0.2V across the 10 kΩ portion of Z5 is connected to the +input
of the differential amplifier. The output of the differential amplifier is routed to the adc
circuit on the DAC assembly, via the RCL line, and measured for 0V ±3% ±15 mV. A
failure indicates the calibration of the 190Ω resistance on the Ohms Main assembly
(A10) is probably at fault.
3400 A12: 8255 Control Word
The diagnostics software reads the control word of the 8255 IC on the Oscillator Control
assembly. A failure indicates the Oscillator Control assembly (A12) is probably at fault.
3401 A12: 8255 Port A
The diagnostics software writes and reads data to port A of the 8255 IC on the Oscillator
Control assembly. A failure indicates the Oscillator Control assembly (A12) is probably
at fault.
3402 A12: 8255 Port B
The diagnostics software reads port B of the 8255 IC on the Oscillator Control assembly
during the instruments dormant state. A failure indicates the Oscillator Control assembly
(A12) is probably at fault.
3403 A12: 8255 Port C
The diagnostics software reads port C of the 8255 IC on the Oscillator Control assembly
during the instruments dormant state. A failure indicates the Oscillator Control assembly
(A12) is probably at fault.
3404 A13: 8255 Control Word
The diagnostics software reads the control word of the 8255 IC on the Oscillator Output
assembly. A failure indicates the Oscillator Output assembly (A13) is probably at fault.
3405 A13: 8255 Port A
The diagnostics software writes and reads data to port A of the 8255 IC on the Oscillator
Output assembly. A failure indicates the Oscillator Output assembly (A13) is probably at
fault.