Troubleshooting 35
Signature Analysis
The easiest and most efficient method of troubleshooting microprocessor based instruments is signature analysis (SA).
The SA technique is similar to signal tracing with an oscilloscope in linear circuits. Part of the microprocessor memory is
dedicated to signature analysis and a known bit stream is generated to stimulate as many nodes as possible within a circuit.
However, because it is virtually impossible to analyze a bit stream with an oscilloscope, a signature analyzer is used to
compress the bit stream into a four character signature. By comparing the signatures of the IC under test to the correct
signatures for each node, faults can be isolated to one or two components.
Signature analysis tests are provided for some of the digital circuits on the front panel board, the secondary interface circuits
on the main circuit board, and for models 664xA & 665xA, the GPIB (primary interface) board. The GPIB primary
interface SA tests are given in Table 3-3, SA tests for the front panel are given in Table 3-4, and the secondary interface SA
tests are given in Table 3-5.
References are made to the appropriate SA table from the troubleshooting flow charts or procedures. The following general
rules apply to signature analysis testing.
1.
Be sure to use the correct test setup connections for the specific test.
2.
Note the signatures for Vcc (+ 5 V) and common on the IC being examined. If an incorrect signature is the same as that
of Vcc or common, that pin (or point in the circuit) is probably shorted to Vcc or ground.
3.
If two pins have identical signatures, they are probably shorted together.
4.
If two signatures are similar, it is only a coincidence.
5.
If a signature is incorrect at an input pin, but is correct at its source (e.g., output of previous IC), check for printed
circuit track or soldering problems.
6.
An incorrect signature at an output could be caused by a faulty component producing the output. It can also be caused
by an input short circuit in another component on the board.
Note
After completing an SA test, you must exit the SA mode by turning off power and performing a power-on
reset.
Summary of Contents for 6541A
Page 12: ...12 Verification Figure 2 1 Basic Test Setup CV TESTS CV TESTS ...
Page 18: ...18 Verification Figure 2 3 CC RMS Noise Measurement Test Setup ...
Page 30: ......
Page 32: ...32 Troubleshooting Figure 3 1 Top View with Cover Removed for 655xA 665xA Models Sheet 1 of 2 ...
Page 33: ...Troubleshooting 33 Figure 3 1 Top View with Cover Removed for 655xA 665xA Models Sheet 2 of 2 ...
Page 37: ...Troubleshooting 37 Figure 3 2 Overall Troubleshooting Flow Diagram Sheet 1 of 4 ...
Page 38: ...38 Troubleshooting Figure 3 2 Overall Troubleshooting Flow Diagram Sheet 2 of 4 ...
Page 39: ...Troubleshooting 39 Figure 3 2 Overall Troubleshooting Flow Diagram Sheet 3 of 4 ...
Page 40: ...40 Troubleshooting Figure 3 2 Overall Troubleshooting Flow Diagram Sheet 4 of 4 ...
Page 51: ...Troubleshooting 51 Figure 3 5 No Display Troubleshooting ...
Page 52: ...52 Troubleshooting Figure 3 6 OV Will Not Fire Troubleshooting ...
Page 53: ...Troubleshooting 53 Figure 3 7 OV At Turn On Troubleshooting Sheet 1 of 2 ...
Page 54: ...54 Troubleshooting Figure 3 7 OV At Turn On Troubleshooting Sheet 2 of 2 ...
Page 55: ...Troubleshooting 55 Figure 3 8 Output Held Low Troubleshooting Sheet 1 of 2 ...
Page 56: ...56 Troubleshooting Figure 3 8 Output Held Low Troubleshooting Sheet 2 of 2 ...
Page 57: ...Troubleshooting 57 Figure 3 9 Output Held High Troubleshooting ...
Page 58: ...58 Troubleshooting Figure 3 10 DAC Circuits Troubleshooting ...
Page 60: ...60 Troubleshooting Figure 3 13 Serial Down Troubleshooting Sheet 1 of 2 ...
Page 61: ...Troubleshooting 61 Figure 3 13 Serial Down Troubleshooting Sheet 2 of 2 ...
Page 62: ...62 Troubleshooting Figure 3 14 Secondary Down Troubleshooting Sheet 1 of 2 ...
Page 63: ...Troubleshooting 63 Figure 3 14 Secondary Down Troubleshooting Sheet 2 of 2 ...
Page 64: ...64 Troubleshooting Figure 3 15 Slow Down Programming Troubleshooting ...
Page 65: ...Troubleshooting 65 Figure 3 16 Isolator Board Circuits Troubleshooting ...
Page 80: ......
Page 87: ...Principles of Operation 87 Figure 4 4 Output Power and Control Circuits ...
Page 94: ......
Page 136: ......
Page 145: ...Figure 6 1 Power Supply Interconnection Diagram for All Models ...
Page 146: ...Figure 6 2 AC Power Distribution Diagram for 655xA 665xA Models ...
Page 147: ...Figure 6 3 GPIB Board Assembly Diagram sheet 1 of 2 ...
Page 148: ...2 3 4 1 6 5 7 8 Figure 6 3 GPIB Board Schematic Diagram sheet 2 of 2 ...
Page 149: ...Figure 6 4 Front Panel Board Assembly Diagram sheet 1 of 2 ...
Page 150: ...Figure 6 4 Front Panel Board Schematic Diagram sheet 2 of 2 ...
Page 152: ...Figure 6 5 A1 Main Board Assembly Diagram for 654xA 664xA Models Only ...
Page 160: ...Figure 6 6 Left Tunnel Circuits Schematic Diagram for 654xA 664xA Models Only sheet 2 ...
Page 162: ...Figure 6 7 Right Tunnel Circuits Schematic Diagram for 654xA 664xA Models Only sheet 2 ...
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Page 168: ......