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Classroom Code Practice Oscillator
VEC-254 Owner's Manual
Classroom Code Practice Oscillator
1
INTRODUCTION
The VEC-254 is the finest keyed oscillator on the market. Its professional
quality is well suited for demanding classroom use and abuse. The VEC-254's
unique design removes any harsh key clicks. Making the VEC-254 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 VEC-254 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 VEC-254 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
adapter 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 VEC-
254. 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 VEC-
254 is ready to use. Push in the power switch to the On position and verify that
the indicator labeled "Pwr" is lit. VEC-254 Owner's Manual
Classroom Code Practice Oscillator
2
WARNING: Do Not Place The Output Speaker Of This
Unit In Close Proximity To Your Ears. The
Amplification On This Unit Is Very High And
Could Cause Damage.

The volume control for the VEC-254 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 VEC-254 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 VEC-254 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.

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 VECTRONICS at 601-323-5800.
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 VECTRONICS, 1007 HWY 25 South,
Starkville, MS 39759 or by Fax to 601-323-6551. 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
VEC-254 Owner's Manual
Classroom Code Practice Oscillator
3
P/N DESCRIPTION
REFERENCE
100S-2100
100 RESISTOR
R17
100S-3100
1K RESISTOR
R4,R11,R14
100S-3390
3.9K RESISTOR
R7
100S-3470
4.7K RESISTOR
R2,R13
100S-4100
10K RESISTOR
R1,R6,R8,R12,R16
100S-4270
27K RESISTOR
R5
100S-4470
47K RESISTOR
R9,R10
100S-5150
150K RESISTOR
R3
100S-5330
330K RESISTOR
R15
130-5100
100K TRIMPOT
R20
155-3100-1
1K POT
R22
155-4100-1
10K POT
R21
200S-1110
.01
µ
F CAPACITOR
C6
200S-1122
.022
µ
F CAPACITOR
C2,C3
200S-1210
.1
µ
F CAPACITOR
C4,C5
203-1470
470
µ
F, ELECTROLYTIC CAPACITOR C7,C8
203S-3110
1
µ
F CAPACITOR ELECT
C1
300S-0914
1N4148 SWITCHING DIODE
D1,D2,D3,D4
305-7002-SM 2N7002
TRANSISTOR
Q1
307-1020
+8V VOLTAGE REGULAR
U2
311-0040-SM LM324 OP AMP
U1
311-27052
TDA7052AN AUDIO AMP
U3
320-1002
3mm RED LED
CR1
410-0169
3" 8 SPEAKER
SPK1
504-0022
2P2T PUSH BUTTON SWITCH
SW1
601-0012
1/4" PHONE JACK
J3
601-5005
3.5mm CLOSED STEREO JACK
J2
601-6021
2.1mm COAXIAL, POWER JACK
J1

VEC-254 Owner's Manual
Classroom Code Practice Oscillator
4
SCHEMATIC