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` PR-8210-A
5-9
LSPS
Voltage
vs.
current
characteristic
of the laser
tube is anagolous
to that of a voltage regulator like
thyratron.
An
ignition voltage of 7 to ЭКУ must
be applied between
its anode and kathod to ionize
the Neon gas filled in the laser tube.
Once the laser has started to light. less voltage
is required to mainiain the lighting compared with
ignitting term.
And the voltage between the anode
and the kathod
is settled to a constant voltage of
1,150vdc.
It doesn't
depend
on
the
value
of
current flow.
АП
Laser
Power
Supply
circuit
except
laser
tube
and
ballast
resistor
is concentrated
ол
the
LSPs board (VWR-0111.
Voltage multiplying recti-
fier
which
has
been
employed
in PR-7820
and
VP-1000
is not empioyed
in this model. Instead of
that. an ignition transformer is adopted to obtain
the ignition voltage.
Both
this transformer
and à
secondary
voltage doubler
are enclosed
їп а case
with resin mold.
and mounted
on LSPS board as
IG block.
In this ignition form, IG block is only activated
until the laser starts lighting. іп the player stand-by
term as the laser-lighting is not necessary and in tbe
lid opening term as the laser should not be lighting.
it is easy to turn the laser off by electrical control-
ing of the LSPS.
Therefore.
the laser tube is pro-
longed
it's life, also а beam
shutter
mechanism
becomes unnecessary.
Laser
tube
and
LSPS
circuit
are
shown
in
Fig. 37.
When
the
PLAY
key
is depressed
after the
power is turned on, LASER ON signal is applied to
pin 12 of the LSPS from CONT board. It turns the
output
of the inverter
consist
of 91 to "high".
therefore
the
darlington-connected
Q4.
95
are
turned on. Consequently, the multi-vibrator consist
of Q2, Q4, Q5, DS, 06, R14,
R17, C9 and C10
starts to oscillate. The oscillation frequency is con-
cerned
by the time constant of R14/C9 and R16;
C10, and is about 20kHz. The output of the multi-
viblator
passes
through
the darlington-connected
Q6, 07, and drives the primary winding of the igni-
tion transformer.
DC voltage of around 8 to 10kV
(peak value) appears on the output of secondary
voltage doubler,
and is impressed to the anode of
the laser tube.
On the other hand, around 2,100Vde appears
on the output of the voltage doubler with 775Vac
inputs. That voltage is varied by the line voltage.
Q10 is turned on by LÁSER ON signal, then dis-
charge current is ready to flow. On the order of
3ms or less while ignition voltage is impressed, the
laser tube starts lighting, and the discharge current
38
flows.
Due
to
tnis. Q9
is reverse-biused
by the
voltage-drop on R31,
Q3 is turned on.
and oscila-
tion of the multi-vibistor is stopped.
Accordingly.
the operation of IG block ts stopped.
At the same time, the
discharge eurreni is stabi-
lized
to 5mA
by Q10. СТ, CS, ВТ connected
in
series
between
coilector
and
emitter
Q10
operate
for reducting
the ripple or. the discharge
current and the serge voltages. R1 to RG connected
in parallel
among
each
Cl
to C6 of the voltage
doubler equahze the voltage applied on each capa-
сот,
and
prevent
reverse-charge
for those by the
discharge current when the power is
ed off.
When
the laser doesn't
start
üghting
notwith-
standing impression
of ignition voltage by deterio-
"һе
laser
заре. Q9 is turned
off by the
output
of
the
level
detector
consist
of
D7,
08,
Cll.
C12,
Qs.
etc.
And
the
oscillation
of the
multi
ibia
is stopped. 09:
ine
ration
«
turned on again on
of 1 sec
os jess, the oscilauen
of the
multisiblacor will
re-start, and the operation of the
GY
ignitting will be repeated.
Fig. 37
LSPS block diagram
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