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Troubleshooting Digital Logic ICs
Comparison testing is a very powerful and effective test strategy when troubleshooting digital
logic using TSA. The Tracker 2700's Alt feature makes this technique quick and simple. Instead
of having to remember the specific signatures of a good component, all that's needed is to have
a reference component or board along side the one that's suspect. This section gave many
examples of signatures from TTL, Schottky TTL and CMOS logic families. Although from first
inspection, these signatures appear to be complex, remember that each of the ICs in the
examples had really only four unique signatures (buffer input, buffer output, power supply VCC
and power supply ground). We can use this characteristic to develop an effective model for
troubleshooting digital logic chips.
Figure 7-9. Tracker 2700 With Test Leads Setup For Comparing 2 ICs
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