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Model
5315A/
B
Service
8-58.
The
amplifier
assembly
provides
separate low
and
high
frequency
buffer amplifiers. The
low
frequency path
is
through
a dual-FET totem-pole configuration
made
up
of Q4A and Band
associated
compone nts.
R32
allows
a
slight
offset adj
ustment
to ba
lance the
circuit. The
high
frequen
cy buffer
ampli
fier, comprised of
C8, C12, C18,
R14,
R15,
R16, an Q3,
is
a simple ac-
coupl
e
d,
emitter-follower
with
dc biasin
g.
Its
output
is
combined
with
the low frequen
cy
amplifier and
appli
ed
to
one side of comparator U2. The
dc
level
from
the
Trigger
level
control
is
applied
to the ot
he
r input. The
complementa
ry
ECl outputs
of the
comparator are input to
a
differentia
l amplifier,
within transistor
array Ul.
Th
e
differential amplifier
serves
to
level
shift
the
Channel A signal
,
before
routing
it to the MRC.
The
MRC
requires
a
uniq
ue
logic
level
of <><+2.4
(logi
c
lowl,to
+3.0
volts
(logic
high).
8-59.
An
additiona
l
differential
pair,
within U3,
form a one-shot.
This
circuit
monitors
the
complementary output
of
U2,
and
drives
th
e Trigge
r
light
on A3.
CR1
keeps
U3
from
going
into
sat
urat
ion, which allows it
to
capture narrow pu
lses
from
the
comparator.
8-60.
OPTIONS THEORY (OPTIONS
002
AND
001)
8-61. A6 BaHery Ch.uger Assembly Option 002
8-62.
The 531
5A
Battery-Pack,
Option
002,
consists
of
a
6-volt
rech argea
ble lead-acid
batte
ry
and the
A6
Charger Assembly.
It
provides
up
to
4
hours
of
continuous,
portable
operation
be
-
tween charging
cycles, an
d
operates two
front
panel
annunicators
which
indicate
the
level of
battery charge
and activity
of charge
circuitry. The
overa ll
opera tion
of
the Battery-Pack
assembly
is
determined
by
the
position
of
~he
front
panel
STBY-ON
switch and the AC
line
cord,
as
descri bed
in
Table
8-2.
The
re
are
three
basic
fun ctional modes for
the A6
Charger
Assembly;
Battery
Charging
cycle,
Battery
Discha
rge
cycle, and an
Idle
mode.
The following
paragraphs
describe the
ope ratio
n
of
the
Charger
assembly
by funct iona
l
mode,
and
reference the
block
diagra
m
in
Figure
8-3. Immediately fo llowing
the
block
descriptio
n
is
the
detailed
circuit
theory,
which
refe rences the
A6
schematic
diagram,
Figure 8-9.
Tab
le
8-2.
Bauery-Pack
O peration
AC
Line
Cord
POWER Switch
!bitely-Pull:
Oper.il.tion
Connected
S
TBY
Two-ste
p battery charging
cycle active
with Charge
Light
annunciator
circui try operative.
Connected
ON
Counter
operat
es
from
AC
power;
charge
ci rc
uitry
provides
a
10
rnA
.trickle
charge to
battery
to
maintai
n
charge
level.
Disconnected
S
TBY
None.
Disconnected
O
N
Cou nter operat
es
fr
om
battery power;
Discharge light
annu
nciator, Auto
-Shut
Down,and
DC-Io-DC
converter
circuitry
operative.
8-63.
Battery
Charging
Cycle
8-64. The
c
hargi
ng
cycle
provides
a 2·step constant
cu
rrent
charge,
utilizing a 500
mA
current
regu
lator
and/
or
a
10
mA
cu rrent regulator connected
in pa
ra
llel. Both regulators operate off the
unregulated
+DC
voltage
from
the
main power
su pply.
The
10
mA reg ulato
r
runs con
ti
nuously.
The 500
mA regulator
cycles
on and
off, controlled by
a
Charge
Compato
r
which monitors
the
voltage
level
of the battery.
Both the
charge
comparator
and
the
SOO mA regulator reference are
controlled by
the
2.5V
reference
regulator.
The
500
mA
regulator
is
automatically
disabled when-
ever
the line
cord is
connected and
the
POWER switch
is
in the
ON
posi
ti
o
n
by
the
+5V line from
motherboard power
supply.
At the beginning of
the cycle,
the
total
curren
t through the
batte ry
is
500
mA,
which
is
th
e
combination
of
the
500
mA
(typically
490
rnA)
and the
10
mA
regulators.
When
the
batte ry vol
tage reaches
near
full
charge,
the charge comparator disables
the
500 rnA
B·9
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