Fluke 2635A, 2625A service manual General Troubleshooting Procedures, Preregulated Power Supplies

HYDRA

Service Manual

Table 5-1. Error Codes (cont)

Error

Error b

Error C

Description

A/D RAM test failure

Complementary patterns are alternately written to and read from each location of the 256 bytes of RAM internal to the 6301Y Microcomputer (A3U9).

A/D self test failed

The Analog Measurement Processor (A3U8) is programmed to do self test measurements.

5-4. General Troubleshooting Procedures

Hydra allows for some fault isolation using self-diagnostic routines and descriptive error codes. However, these features are somewhat limited and do not provide in-depth troubleshooting tools.

Hydra incorporates a semi-modular design; determining modules not related to a problem constitutes the first step in the troubleshooting process.

As a first step, remove the IEEE-488 Option (if installed) from the Data Acquisition Unit (2620A) or the Memory PCA from the Data Logger (2625A). Refer to Section 3 of this manual for removal procedures. If removal of either of these assemblies results in improved instrument operation, refer to Section 7 for IEEE-488 Option troubleshooting or later in this section for Memory PCA troubleshooting.

Measuring the power supplies helps to isolate a problem further. Refer to Table 5-2 and Figure 5-1 for test point identification and readings. If power supply loading is suspected, disconnect the Display PCA at A1J2. If this action solves the loading problem, proceed to Display Assembly Troubleshooting elsewhere in this section. Otherwise, refer to Power Supply Troubleshooting.

Table 5-2. Preregulated Power Supplies

PREREGULATED VOLTAGE

-9.0V -30V +9.25V -8.75V

MEASUREMENT POINTS

A1CR13-2 to A1TP1 A1TP4 to A1TP1 A1CR5 cathode to A1TP30 A1CR7 anode and A1TP30

RESULTING SUPPLY

VEE

VLOAD

VDD, VDDR

VSS

If the power supplies appear good, check the E clock signal to determine whether the Main PCA or the Display PCA is causing the problem. A correct display depends on the E clock signal. Missing segments, intensified digits, a strobing display, or a blank display can be caused by a faulty E clock.

Use an oscilloscope to check for the E clock at Microprocessor A1U4, pin 68. Look for a 1.2288-MHz square wave that transitions from 0 to 5V dc (VCC).

∙If this signal is present, the Display PCA is probably faulty. Referto Display Assembly Troubleshooting elsewhere in this section.

∙If the E clock is something other than a 1.2288-MHz square wave,isolate the digital section of the Main PCA by disconnecting theDisplay PCA at J2. Then check the E clock again, and refer to DigitalTroubleshooting elsewhere in this section for further problemisolation.

Refer to the Schematic Diagrams in Section 8 during the following troubleshooting instructions. Also, these diagrams are useful in troubleshooting circuits not specifically covered here.

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