MFJ MFJ-554 User Manual

MFJ-554 Instruction Manual Classroom Code Practice Oscillator

INTRODUCTION

The MFJ-554 is the finest keyed oscillator on the market. Its professional
quality is well suited for demanding classroom use and abuse. The MFJ-554's
unique design removes any harsh key clicks. Making the MFJ-554 a perfect
complement to any keyer paddle. This unit enhances classroom instruction of
Morse Code by delivering a full watt of power to the internal 3 inch speaker.

Key clicks can be especially annoying in high output units where they tend to
bounce around the room. The MFJ-554 produces a true pure sinewave so you'll
hear the clearest sounding tone you have ever heard from a code practice
oscillator. You'll get low distortion CW--typically less than .2% total harmonic
distortion from its BTL (Bridge-Tied-Load) amplifier.

FRONT PANEL

Power (On/Off) ...............................Power Switch

Volume............................................Volume Control

Tone................................................Tone Control

Pwr..................................................Power Indicator

Key Input.........................................1/4" Phone Jack

REAR PANEL

Power ..............................................2.1mm Coaxial Jack

Ext. Speaker....................................3.5mm Speaker Jack

OPERATION

The MFJ-554 requires a 12V source for power operation. The power jack
accepts a 2.1mm coaxial type plug with the outside sleeve as the ground pole and
the inside as the positive pole. Apply power to the unit by plugging a power
adaptor to the jack on the back of the unit labeled "Power". With the switch in
the Off position (out), connect a keyer paddle to the "Key Input" of the MFJ-

554. The Key Input requires a 1/4" mono or stereo plug with a 2-conductor wire
from the keyer. The sleeve is connected to ground and the other wire is
connected to the tip. Once the power and keyer have been attached, the MFJ­554 is ready to use. Push in the power switch to the On position and verify that
the indicator labeled "Pwr" is lit.

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MFJ-554 Instruction Manual Classroom Code Practice Oscillator

WARNING:WARNING: Do Not Place The Output Speaker Of This UnitDo Not Place The Output Speaker Of This Unit

In Close Proximity To Your Ears. TheIn Close Proximity To Your Ears. The
Amplification On This Unit Is Very High AndAmplification On This Unit Is Very High And
Could Cause Damage.Could Cause Damage.

The volume control for the MFJ-554 is located on the front of the unit. To
increase the output volume, push in the power switch to the On position, key the
keyer and turn the knob labeled "Volume" in the clockwise direction. The tone
control is also located on the front of the unit. With the volume at a comfortable
level and the keyer keyed, adjust the tone by varying the knob labeled "Tone".

To use the MFJ-554 with the optional external speaker, plug a speaker, with a

3.5mm plug, into the jack labeled "Ext. Speaker". This jack is located on the
back of the unit.

The MFJ-554 comes with a trimpot to generate a symmetrical rise time and fall
time of the input signal. This feature eliminates the unwanted key clicks that are
normally heard from keyers. The setting on this trimpot (R20) is made at the

factory and should not be changed.

To add even more output to your unit, the MFJ-281 ClearTone speaker is
available to all MFJ customers.

TECHNICAL ASSISTANCE

If you have any problem with this unit first check the appropriate section of this
manual. If the manual does not reference your problem or your problem is not
solved by reading the manual you may call MFJ Technical Service at 601-323-
0549 or the MFJ Factory at 601-323-5869. You will be best helped if you have
your unit, manual and all information on your station handy so you can answer
any questions the technicians may ask.

You can also send questions by mail to MFJ Enterprises, Inc., 300 Industrial
Park Road, Starkville, MS 39759; by Facsimile to 601-323-6551; or by email to
[e-mail]. Send a complete description of your problem, an
explanation of exactly how you are using your unit, and a complete description
of your station.

PARTS LIST

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