Tracker-2800-2800S.pdf - 第83页
83 Linear Voltage Regulators Voltage regulators are comm only found in man y electronic assemblies. Some of the most popular integrated circuits of this t ype are three terminal devices li ke the 7805, a +5 volt DC regul…
82
Pin 2 –Input Pin 3 +Input Pin 6 Output
Figure 5-10. Signatures of an Op Amp (741) at 10V, 50, 60Hz with Common to Pin 4.
Pin 2 -Input Pin 3 +Input Pin 6 Output
Figure 5-11. Signatures of an Op Amp (741) at 20V, 10K, 60Hz with Common to Pin 4.
Troubleshooting OP Amp Circuits
Troubleshooting an op amp in-circuit may be very challenging. These circuits usually have numerous
connections that act as feedback or compensation loops. This results in almost an infinite number of
possible analog signatures. Use the comparison test method when troubleshooting op amps in-circuit.
In this case, components on a suspect board are compared to those on a known good board. The
Tracker 2800 can help locate the defective component quickly.
The op amp has three main terminals; + input, - input and output. An alternative way to perform ASA
on the op amp is to connect Tracker 2800's Common terminal to the op amp's output while making a
comparison with the red test probe to the “ + ” and then the “ - ” leg. This eliminates problems
encountered when probing op-amps that are isolated from power and common. When there is more
than one op amp in a package, compare one with the other. The dual op amp and quad op amps are
very common. This technique also works with comparators.
83
Linear Voltage Regulators
Voltage regulators are commonly found in many electronic assemblies. Some of the most popular
integrated circuits of this type are three terminal devices like the 7805, a +5 volt DC regulator. The
next figure shows the schematic and pin layout of the 7805 regulator. Different manufacturers
implement their products with different topologies and manufacturing processes. So it's not unexpected
that the same functionally equivalent component from different manufacturers may have different
signatures.
Figure 5-12. Diagram and Symbol of a Linear Voltage Regulator, 7805 Type
Input pin Output pin
15V, 1K, 200Hz with Ground Pin to Common
Figure 5-13. Signatures of a 7805 SGS Thompson Voltage Regulator
Input Output pin
15V, 1K, 200Hz range, Ground Pin to Common
Figure 5-14. Signatures of a 7805 Motorola Voltage Regulator
Review
Integrated circuits are complex devices that are built using basic electronic components.
84
The IC signatures resemble zener diodes.
There are many causes for IC failures and the Tracker 2800 can display its "health" as resistive
leakage, an open or a short.
Functionally identical pins on a single IC out-of-circuit will display the same signature.
The most common point for reference is ground, but V
CC
or another point might give a more
informative signature.
Different analog IC families exhibit different characteristic signatures.
Applications
Testing for faulty IC’s is one of the more common uses for the Tracker. A technician can compare IC’s
in or out of circuit.