EZ Digital FG-7005C Operation Manual - page 21
5. OTHERS
5-1. Introduction
Because of the great versatility of this Sweep/Function Generator, it would be
impossible to include all of its possible applications in this manual, However ,many
of the primary applications are described in detail to allow the user to adapt the
procedures to other applications. The instrument has vast numbers of applications
as a signal source in electronics design labs, classrooms, service shops and
production facilities to test or analyze audio, radio, digital, communications, medical
electronics, sonar, industrial electronics, subsonic, ultrasonic and many other
electronic devices and circuits.
5-2. Troubleshooting By Signal Substitution
When troubleshooting dead audio equipment, localize the trouble by injecting an
audio signal from Sweep/Function Generator to substitute for the normal signal.
Starting at the nearest speaker and moving toward the audio input area, Step By
Step, sound will be heard from the speaker for each stage that is operating normally.
When signal is applied to the defective stage, no sound will be heard from the
speaker.
CAUTION
MAKE SURE THE DC OFFSET MATCHES THE NORMAL OPERATING VOLTAGE AT
EACH POINT OF SIGNAL INJECTION. IMPROPER DC OFFSET COULD BIAS A
NORMALLY OPERATING STAGE TO CUT OFF AND MAKE IT APPEAR DEFECTIVE.
IMPROPER DC OFFSET COULD ALSO DAMAGE CERTAIN CIRCUITS. A COUPLING
CAPACITOR MAY BE USED TO BLOCK THE DC OFFSET AND ALLOW THE SIGNAL TO
FLOAT AT THE DC LEVEL OF THE POINT OF INJECTION IF DESIRED.
The signal amplitude should also simulate the normal signal levels used in the
circuit where signal is being injected. This technique is equally applicable to non
audio equipment. Just connect an oscilloscope, voltmeter, or any other device,
which will indicate the presence or absence of output. Inject the type of signal
normally used by the equipment being tested. This instrument can generate almost
any type of signal normally required in the 0.05 Hz to 5 MHz range. If the equipment
under test, It can generate unique sounds or signals by means of sweep that should
be easily distinguishable from any other signals that may be present.
5-3. Troubleshooting By Signal Tracing
This technique is similar to “Troubleshooting by Signal Substitution” except that the
signal is injected at the input of the equipment under test. An oscilloscope is then
used to check for output at each stage, starting nearest at the input area and
moving toward to the output area. Each stage, which has no output, is presumed to
be defective.