Operating Principle - Panasonic Technics SL-1600M Service Manual

The state under which the strobe dots seem to be
stationary represents the correct number of revolu-
tions.
direction
This increases the speed of the turntable rota tion, and
the strobe dot pattern seems t o flow in the same
direction as the rotational direction of the turntable
platter.
direction
This decreases the speed of the turntable rotation,
resulting in a state opposite t o that in the
tion.
Note:
Strobe dot pattern.
The strobe illuminator/pilot lamp of this unit employs
the commercially available power source. The frequency
of such power source, when actually measured, has a
fluctuation of about 0.2%. As such a fluctuation of the
Cross section of motor portion and double insulator
Operation principles of the SL-1600
This unit, like the S L 1300 has a rational motor structure, and its drive control circuit is the B.F.G. type (Back
TECHNICAL EXPLANATION electromotive force frequency generator) which is constructed on a single integrated
circuit (IC) chip (AN630). The following is a block diagram of the IC (AN6303 for which the operating principle will
be briefly explained

Operating principle

The back electromotive force, which is generated by the
drive coil winding according to the rotation of the
motor, is detected and converted to a frequency signal
that is proportional t o the numder of revolutions.
Conversion is performed by a wave-shaping circuit and a
logic circuit (This is referred t o as the B.F.G. method).
This frequency signal is compared with a standard signal
by means of a frequency-voltage conversion circuit
which converts it to a voltage signal in order maintain a
constant number of revolutions.
necessary
direc-
Motor shaft (Center spindle)
Stator
I
\
Main base
After removing un-
www.vinylengine.com
power source affects the strobe illuminator, the strobe
dot pattern also seems t o fluctuate t o a certain extent.
But the unit is not affected by -the fluctuations of the
power source, since a D.C. motor is employed.
I f the desired speed can not be obtained b y the variable
pitch controls, turn the speed adjusting screws w i t h a
screw driver for further adjustments. (See Fig.
Position detecting rotor
Position detecting coil
frame
frequency components, with -the operational-amplifier
active filter, from this voltage signal, i t controls the cur-
rent flow in three differential switching circuits.
result, the f l o w of current in the drive coil winding is
always constant maintaining the correct rotational spe-
ed. Control of the rotational speed can be performed by
means of adjusting the standard signal generator circuit
according to the rotational speed adjustment cricuit.
9)
Dust cover
A r m base
As a