THORENS TD125 - Page 18

THE SOLID STATE CONTROL
SYSTEM AND HOW IT WORKS.
The TD 125 turntable is fitted with a Solid State Control
System. This replaces the mechanical linkage which is
normally necessary to maintain different record speed:
The Solid State Control Circuit consists of a transi
The necessary power for the synchronous motor is
produced by a push-pull amplification stage. To main-
tain
the
optimum
torque
from
the
motor
at
any
fre-
quency, a pair of frequency stepped switches are linked
torized Wien bridge oscillator, normally used in meas-
turing instruments, and the frequency of this oscillator
can be varied in definite steps so that the speed of the
16 pole synchronous motor can be changed. An additio-
nal fine frequency adjustment may be effected by
means of a potentiometer, thus providing an electronic
speed control within the range of + 2%.
13
Fig. 8
together thus providing different phase shift motor con-
densers.
The speed of the synchronous motor is therefore con-
trolled by the generated frequency. The desired record
‘speed will be provided by the precise frequency varia-
tion of the control generator.