Fluke 5720A service manual 3605 -42S Supply Fault, LH Com Ground Fault, 3607 -5lH Supply Fault

Troubleshooting 5

Interpreting Diagnostic Fault Codes

Crossing assembly (A17) is faulty. If the voltage is within tolerance, the diagnostic circuit on the Oscillator Output assembly (A13) is faulty.

3605 -42S Supply Fault

The instrument is dormant and the -44 S supply is out of tolerance. Measure the unregulated -44 S voltage on the Filter/PA Supply assembly (A18). COM = TP22, HI = TP9. The voltage should be -45V to -75V. If the voltage is out of tolerance, the Filter/PA Supply assembly (A18) is faulty. If the voltage is within tolerance, measure the regulated -44 S on the Regulator assembly. (A17) COM = TP9, HI = TP16. The voltage should be -42.0V to -45.6V. If the voltage is out of tolerance, the Regulator/Guard Crossing assembly (A17) is faulty. If the voltage is within tolerance, the diagnostic circuit on the Oscillator Output assembly (A13) is faulty.

3606 LH Com Ground Fault

The Current/Hi Res assembly (A7) connects LHCOM to the SDL line where it is measured by the adc circuit on the DAC assembly for 0V ±50 mV relative to RCOM.

3607 -5lH Supply Fault

The instrument is dormant and the -5 LH supply is out of tolerance. Measure the unregulated -5 LH voltage on the Filter/PA Supply assembly (A18). COM = TP3, HI = TP6. The voltage should be -8V to -16V. If the voltage is out of tolerance, the Filter/PA Supply assembly (A18) is faulty. If the voltage is within tolerance, measure the regulated -5 LH on the Regulator assembly. (A17) COM = TP10, HI = TP15. The voltage should be -4.7V to -5.3V. If the voltage is out of tolerance, the Regulator/Guard Crossing assembly (A17) is faulty. If the voltage is within tolerance, the diagnostic circuit on the Switch Matrix assembly (A8) is faulty.

3608 +5rLH Supply Fault

The instrument is dormant and the +5 RLH supply is out of tolerance. Measure the

+5 RLH voltage on the Regulator/Guard Crossing assembly (A17). COM = TP10, HI = TP14. The voltage should be +4.9V to +5.5V. If the voltage is out of tolerance, the Regulator/Guard Crossing assembly (A17) is faulty. If the voltage is within tolerance, the diagnostic circuit on the Switch Matrix assembly (A8) is faulty.

3609 +8RLH Supply Fault

The instrument is dormant and the +8RLH supply is out of tolerance. Measure the +8RLH voltage on the Regulator /Guard Crossing assembly (A17). COM = TP10, HI = TP17. The voltage should be +10V to +20V. If the voltage is out of tolerance, replace fuse F1 on the Regulator/Guard Crossing assembly. (A17) If the voltage is within tolerance, the diagnostic circuit on the Switch Matrix assembly (A8) is faulty.

3610 +PA Supply Fault

The instrument is configured to the dc 220V range. The Power Amplifier is set for 22.1V, 219V, and -219V and the +PA supply is measured for the nominal +180V and +360V ±10% by connecting MUX1 to the SDL line which is measured by the adc circuit on the DAC assembly. In order to identify the faulty assembly the +PA supply will have to be measured. Power off the instrument and remove the Power Amplifier assembly from the chassis.

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