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Troubleshooting
Interpreting Diagnostic Fault Codes
5
5-27
3503 A16: 8255 Port C
The diagnostics software read port C of the 8255 IC on the Power Amp assembly. A
failure indicates the Power Amp assembly (A16) is probably at fault.
3504 Spare
This fault code is not used.
3505 Spare
This fault code is not used.
3506 Spare
This fault code is not used.
3507 A16: PA Supplies Are Off
The instrument is dormant. The +PA and -PA supplies are measured by connecting
MUX1 and MUX2 respectively to the SDL line where they are measured by the adc
circuit on the DAC assembly. This failure occurs if the measured voltage is between 40-
80V. The test switch S201 on the Filter/PA Supply assembly (A18) appears to be in the
test position.
3508 A16/A14: 220V AC Range Output Fault
The instrument is configured for operation at 22.1V at 1 kHz, 22.1V at 100 Hz, 100V at
1 kHz, 100V at 80 Hz, 100V at 500 Hz, 219V at 1 kHz, and 219V at 50 Hz. The output
of the Power Amplifier is routed to the High Voltage Control assembly where it is
divided and converted to a dc voltage by a peak detector circuit. This dc voltage which is
equal to the peaks of the ac amplitude is connected to the SDL line where it is measure
by the adc circuit on the DAC assembly to be the nominal ±10%. Exit diagnostics and
set the instrument for the previous configuration and using a DMM measure the ac
voltage output of the Power Amplifier, COM=TP10 HI=TP6. If the voltage is out of
tolerance the Power Amplifier assembly (A16) is probably at fault. If the voltage is
within tolerance, the the High Voltage Control assembly (A14) is probably at fault.
3509 A16: Amplifier Loop Not Regulated
The instrument is configured into three modes of operation. The first two modes is with
the instrument set to the dc 220V range. The first is with the Power Amplifier input
voltage being the 6.5V reference voltage (BRF6, BSRF6) resulting in a -130V Power
Amplifier output. The second is the normal 220V dc operation with the input voltage
from the DAC assembly. In this mode the Power Amplifier is outputting 22.1V, 100V,
219V, and -219V. The third is the ac 220V range at 22.1V at 1 kHz, 22.1V at 100 Hz,
100V at 1 kHz, 100V at 80 Hz, 100V at 500 Hz, 219V at 1 kHz, and 219V at 50 Hz. The
output of the Power Amplifier input stage is measure to be less than 11V by connecting
MUX0 to the SDL line where it is measured by the adc circuit on the DAC assembly. A
failure indicates the Power Amplifier assembly (A16) is probably at fault.
3510 A16: 220V Amp Fault
The instrument is set to the dc 220V range with two modes of operation. The first is with
the Power Amplifier input voltage being the 6.5V reference voltage (BRF6, BSRF6)