MFJ MFJ-5012 User Manual

MFJ-5012 MFJ Portable Signal Tracer/Injector Owner's Manual

INTRODUCTION

The multi-purpose MFJ Portable Signal Tracer/Injector is used to quickly find

defective stages in all kinds of signal amplifier s, radio receivers, and transmitters.
This includes home theater systems, hi-fi amplifiers, public address systems,
guitar amplifiers, AM/FM/ TV receivers, CB radios, Ham transceivers, cordless
phones, police scanners, shortwave receivers and cell phones.
It can also be used to find opens and shorts in cables and wires. It can identify and
locate individual wires in multi-conductor cables. It's perfect for trouble shooting
and repairing the cabling and wi ring in computer networks, telephone s, home t hea ter ,
stereos, sound systems, public address systems and almost any system that uses
wiring and cablin g.
The MFJ Portable Signal Tracer/Injector accomplishes these functions with a
harmonic rich variable level signal source, an AM detector and a variable gain
audio amplifier.

CONTROLS AND CONNECTORS

MFJ-5012 MFJ Portable Signal Tracer/Injector Owne r's Manual

2. Signal Level: This kn ob tu rns the signal ge nerator on and controls the amount

of signal injected into the device under test.

3. AM Detector: This switch turns the detector on and off.

4. Audio In: The audio signal from the device under test enters through this

terminal.

5. Ground: The ground of the device under test is connected to this terminal. 6.

Signal Out: The output of the signal generator is located at this terminal. 7.
Speaker: Audio from the device under test is heard through the speaker.

The MFJ-5012 is power by a 9 volt battery. The battery connector is accessed by
removing the four screws on the cover. There is a holder mounted in the bottom
of the box for the battery

OPERATION

There are two basic ways or techniques to test amplifier stages in a device using the
MFJ Portable Signal Tracer/Injector. These two techniques are reflected in the
name itself. The first way is by signal tracing. This is accomplished by
checking for a signal and/or a signal increase at each stage of the device under
test. The second technique is signal injection. This is done by introducing a
signal at each input stage of the device under test and checking for an outpu t.

Signal Tracing

The signal tracing technique is applying a signal to the main input of the _device

Wider lest (DUT) and then checking for the pr esence of the si gnal at the input a n d
output of each stage. When a stage with an input and no output is found,
chances are the problem area has been located. W ith the DUT and MFJ-5012 off
(both level controls and AM detector), connect the DUT ground to the MFJ5012
ground terminal. Connect a wire or something you can probe with to the Audio In
connector and connect the Signal Out connector to the input of the DUT. Keep all
connections as short as possible, especially the ground connection. Turn the
Audi o Level c ontrol a nd the Si gnal Le vel cont rol on. Place both controls in the
12 o'clock position. This is just a starting point; you will have to adjust these
controls to accommodate the device that is being tested. Next t u r n t h e D U T o n . U s e
the "probe" to check the input and output to each stage from the main in put to
the final output U se the first stage t o adjust the level controls. At each amplifier
st ag e an i nc r ea s e i n si gn a l l e ve l sh o ul d oc c ur . Continue to use the Audio Level control
as needed.

Note: If you are testing a device that's using amplitude mod ulation, make sure the

AM Detector is on.