Fluke 5720A Introduction, Interpreting Diagnostic Fault Codes, 2700 A7 8255 Control Word

Troubleshooting 5

Introduction

5-1. Introduction

Information in this section begins with guidance in using self-diagnostics fault codes to isolate a faulty module. The descriptive text helps to quickly locate the source of a fault. Further on, under Component Level Troubleshooting, techniques for isolating faulty components or circuits are described. The Component Level Troubleshooting is only for qualified service personnel who do not wish to replace a faulty module through the Fluke Module Exchange Program. (Refer to Section 1 for module exchange instructions.)

Warning

To avoid electric shock, disconnect all cables from the output and sense binding posts and do not touch binding post during self diagnostics.

5-2. Interpreting Diagnostic Fault Codes

Run self diagnostics by pressing the "Setup Menus" then the "Self Test & Diags" softkey.

Note

Self test diagnostics of the analog circuitry are carried out with the 5700A/5720A Series II binding posts open circuited. (Cables and test equipment left connected to the binding posts have no effect.)

Test routines connect specific points to the SDL or RCL line and measuring for an expected voltage and tolerance. The SDL and RCL lines are routed to the adc circuit on the DAC assembly for measurement.

Fault code descriptions generally indicate the instrument’s test configuration, point being measured, expected voltage, and probable assembly which is at fault. In some cases, an addition manual measurement may be required to determine the faulty assembly. These manual measurements are Noted with the related fault code description. In all cases it is assumed that the Motherboard assemblies are fully operational. Power Supply faults assume that other, non-power supply related assemblies are not loading down the Power Supply.

2700 A7: 8255 Control Word

The diagnostics software reads the control word of the 8255 IC on the Current/Hi Res assembly. A failure indicates the Current/Hi Res assembly (A7) is probably at fault.

2701 A7: 8255 Port a Fault

The diagnostics software writes and reads data to port A of the 8255 IC on the Current/Hi Res assembly. A failure indicates the Current/Hi Res assembly (A7) is probably at fault.

2702 A7: 8255 Port B Fault

The diagnostics software reads port B of the 8255 IC on the Current/Hi Res assembly. A failure indicates the Current/Hi Res assembly (A7) is probably at fault.

2703 A7: 8255 Port C Fault

The diagnostics software reads port C of the 8255 IC on the Current/Hi Res assembly. A failure indicates the Current/Hi Res assembly (A7) is probably at fault.

5-3