Motion Control; Audio Amplifiers - Elenco Electronics AK-200 Assembly And Instruction Manual

TAPE DECK ASSEMBLY
See Figures 5-3 and 5-5.
Tape Deck Assembly consists of three main parts:
1) Tape Drive Train - The Tape Drive Train contains
a motor which turns at a constant speed. The
motor is connected by a drive belt to a large
pulley which turns the capstan. When the AK-200
is in Play Mode, that is, with the Play button
pushed, the pinch roller clamps the tape against
the capstan. This causes the tape to be pulled
across the head at a constant speed.
At the start of tape play, the tape is winding onto
an empty take-up reel. As the tape builds up on
the take-up reel, it takes more tape to go once
around the reel. Since the tape is moving at a
constant speed, the take-up reel must turn faster
at the start of tape play than at the end. A belt
from the capstan drives a small pulley to turn the
take-up reel. This pulley, if it were rigidly
connected to the take-up reel, would drive the
reel much faster than required even at the start of
tape play. A slip clutch is therefore inserted
between the small pulley and the take-up reel to
allow the reel to turn at the different speeds
required to wind up the tape.
2) Push-button Controls - Three push-buttons
control tape play. Pushing any button places the
AK-200 in that mode until another button is
pushed.
Play - Pushing the PLAY button closes the ON
switch which supplies power to the motor, motion
control and audio amplifier electronics.
addition, the head and tape guide are moved into
contact with the tape and the pinch roller clamps
the tape against the capstan. You may then listen
to the tape through the stereo headphones.
Fast Forward - Pushing FAST FORWARD closes
the ON switch which, as in PLAY mode, supplies
power to the motor, motion control and audio
amplifier electronics. The head, tape guide and
pinch roller are not moved into contact with the
tape. The tape is therefore driven solely by the
take-up reel. Since there is little drag, there is
little or no slippage in the slip clutch and the tape
moves forward at high speed. FAST FORWARD
is used to space forward to a particular section of
tape or, after using the tape over, for rewinding.
Stop - Pushing STOP takes the AK-200 out of PLAY
or FAST FORWARD mode and stops the tape. After
opening the lid, STOP may be used again to pop up
the tape cassette for easy removal.
3) Heads - The purpose of the heads is to convert
the magnetization on the tape into an electrical
signal. The AK-200 has two playback heads.
Each head plays one of the four tape tracks when
the cassette is inserted one way and another
track when the tape is turned over.

MOTION CONTROL

When the two 1.5V batteries are new, they put out
their full 3V rated voltage. In time, as the batteries
are used, this voltage drops. If the battery voltage
was applied directly to the motor, the motor would
slow down as the battery voltage dropped. Tape
speed would then decrease, causing music to be off
key and voices to sound too low.
Control Section is therefore used to keep a constant
voltage on the motor and insure uniform tape speed.

AUDIO AMPLIFIERS

The audio amplifier section consists of two separate
amplifiers, one for each head, each amplifier driving
one of the stereo headphone speakers. The gain of
both amplifiers is set by the thumb wheel on the side
of the tape player.
frequencies from the head is lower than that of the
high frequencies. The frequency response of the
amplifiers is therefore set to emphasize the lows
In
and thus equalize the overall response.
-4-
The Motion
The amplitude on the low