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5.6 The Lamp Driver and Power Supply (LDPS) card
(PL8 on the Motherboard)
The lamp driving parts of this card consist of 10 identical
circuits
drive capability of
tailed
elsewhere
Four
a
single
suppression
through
T14
relays are mounted on this card and the fourth is on the Motherboard,
as RLl,
and controls the illumination of the 'Throw Darts! and
'Remove
Darts'
The +5
of T21,20,19,17
output transistors and are mounted on the heatsinks.
to the 5 volts is made by RVl,
will
increase
determined
circuitry and will maintain the output within 50 millivolts from
no load to 4 amps.
Overcurrent
T15 and T16.
through R17 and R33 is sufficiently high to cause the voltage drop
across
Once conducting they latch themselves on and cause T17 and T18 to be
held OFF.
seconds and then reconnecting will the power supply circuit be reset
for
normal
Over
T22 and SCRl.
the 5 volt line, rises to.around
and five SCRl.
either the overcurrent protection circuit will trip or fuse
slow..
A
further
is provided by zener diode D15 of 5.6 volts, which
the 5 volt line.
and
(notably
further
circuits,
diode
and
associated
captions.
volts
power
supply
and 18 in that sequence.
the
voltage.
by
the
reference
protection
Normally those are off and only when the current
Only by disconnecting power from the machine for about 5
operation.
voltage
protection
Normally there are OFF but if the monitored voltage,
Having
fired, the 5 volt line is pulled down and
small
overvoltage
associated
components)which
The specific lamps they drive are de-
in
the
signal
description
identical except for the addition of
across
the
drive
components)
are
regulator
an
anticlockwise
The stability of the 5 volt supply is
voltage
derived
is
provided
by
is
provided
i-5.5 volts then T22 will conduct
protection
lists).
transistor,
relay
drives.
is
an
amplifier
The latter being the
Adjustment
movement
from
the
circuitry
by
the
'crowbar'
for
very
fast
is
strapped
have
a
Three
consisting
of
which
around
circuit
transients
across
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