Luxman PD-375 - PCB and Switch Adjustments; Full-Auto Mechanism Circuit Alignment; PCB Alignment Procedures; Adjustment of SW-07 (Main Cam SW)

PD-3
FULL-AUTO MECHANISM CIRCUIT ALIGNMENT RROCEDURES
There happen to be eccentric record discs among those which are available in markets
and in case these eccentric ones are used for playing, the wave form will be as per Fig.
1 when the rester lever slit passes through the light axis of the sensor.
f\ of
L GE L
Fig.1
When eccentricity is remarkable, the wave form reads as per Fig. 2 and mis-operation
shall be caused as for EP discs.
H Sensor output
Schmidt Trigger Circuit
Level "H"
Schmidt Trigger Circuit
Level "L"
Sensor output L
Fig.2
As return action is made on EP discs when output of schmidt trigger circuit comes to
be "L" from "H", mis-operation shall be caused at the portion of the enlarged curve in
Fig. 2.
So,
prevent
from
mis-operation,
make
the
hysterisis
as
wide
as
possible
and
adjust
output
level of the sensor to it.
Widening of the hysteresis in schmidt trigger circuit will be efective to prevention of
outcoming noises, etc.
Adjustments of the hysteresis and output level of the sensor are made respectively by
the VRO2 and VRO1 as far as the ‘present circuit is concerned.
In the actual procedures firstly adjust the hysteresis and secondly output level of
the sensor.
The hysteresis is not always same since threshold value of IC's varies depending on IC's
to be used.
So, at first adjust "H" level of schmidt trigger circuit to (x-0.8)V by the VRO2 when
output
of
the
sensor
is
"H"
(saturated
state,
provided
to
be
xV),
and
at
this
point
"L"
level (provided to be yV) of schmidt trigger circuit shall be decided.
Secondly adjust "L" level of output of the sensor to (y-0.6)V by the VRO1.
Above is all for adjustment.
Remarks:
As
to
"H"
level
difference
by
0.8V
is
made
between
threshold
values
of
the
sensor
output
and
schmidt
threshold,
and
as
to
"L"
level
difference
by
0.6V
between
the
threshold
values.
Those
values
are
decided
in
consideration
of
changes
in
temperature,
humidity
and
time
process
and
other
drifts
as
well.