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Model 5245L
-130volts.
Note
that
the
-130volt supplyis the
source
for
shunt regulator A?CR2 which provides -56 volts
to the -15 volt regulator
circuit.
2-69. +l3-VOLT
AND +20-VOLT
SUPPLIES.
The
+13-volt
supply
(Q3, A?Q3,
and
A?Q4; see schematic
Figure 7-7)
is
similar to the -15 volt
supply des-
cribed
in
Paragraph
2-65.
The
only significant
dif-
ference
is
that t}te negative leg
is
grounded
while
the
positive Ieg provides the regulated output.
The
+20
volt supplyis
obtained
by adding a
Tvolt
source
to
the
+13
volt supply.
The
7
volt regulator consists of
Q4
and
A?Q5, both acting as emitter
follorvers. A
?
volt
zener
diode
and a
bias adjustment
circuit
provide
the
reference voltage
for this
supply.
2-70.
DECIMAL
PON.{T
ASSEMBLY
AB.
2-7L.
INPUT.
The decimal point
assembly
holds
eight neon lamps
which are located to the
left
of
each
digital display tube
on the
front panel.
Lamps are
designated
0
through?
from right toleft
as
seen
look-
ing at
the
front panel. The decimal point control signal
consists
of
+1 70
volts applied
to the
desired lamp input.
Control
is
suppliedeitherfromthe TIME
BASE switch
or
the lower
REMOTE CONTROL connector on
the
rear
panel.
2-72.
OUTPUT.
A
group
of
OR gates converts
the
decimal point control signal from decimal form
to
binary-coded
decimal
(BCD) form which
is
supplied
to the
DIGITAL
RECORDER
connector on
the rear
panel.
As an example,
suppose
decimal point 5 is
Iighted; a positive signal
passes
the
OR
gates
and
Iimiters to the
A, B,
and
C
output
lines,
thus
pro-
viding
a
0111 (in
the
order
DCBA) output
to
the
DIGITAL
RECORDER
connector. For circuit
details
refer
to the schematic diagram,
Figure
7-8.
2.73.
MEASUREMENT
I]NITS ASSEMBLY
A9.
2-74. INPUT.
The
measurement
units
assembly
holds
six
neon
lamps which
are
located
on
the
front
panel
at
the
right
end
of t}re counter
display.
Lamps
aredesignated MC, KC,
SEC,
mS,
pS,
and
*(asterisk).
As
with
the
decimal point assembly, the measurement
units control signal consists
of
+170
volts
applied to
the desired lamp
input.
Control
is
supplied either
from the TIME-BASE switch
or
the lovrer
REMOTE
CONTROL connector
on
the rear
panel.
2-15.
OUTPUT.
A
group
of
OR gates converts
the
measurement units control signal from decimal form
to
BCD
form,
just
as
is
done
in the decimal point as-
sembly. The digitwhich
is
printed
for
each
measure-
ment unit
is
given
in
a
table
along
with the
schematic
diagram,
Figure
7-8.
Print
wheels
are available for
Hewlett-Packard recorders sothat the correct meas-
urement
units
symbol
can
be
printed directly.
2-76.
LOW
FREQUENCY
pECTMAL
COUNTER
ASSEMBLY
A1O-A14.
2-77.
The low-frequency decimal counter
is
shown
in
Figure
2-t44.
Note
the
inclusion of clipper
diodes
CR9
through CRl3 which
permit only positive
pulses
02349-1
Section
II
Paragraphs 2-69
to
2-82
to
be delivered
to the
input
base
of
each
transistor.
Operation
of
basic
circuits is
discussed
in the Para-
graphs Iisted in Table
2-3.
Circuit
details are
given
in the
schematic
diagram, Figure
7-9.
Table
2-3.
Basic Operation Summary
of
Four-Binary
Counter
2-78.
5
MHz
DECIMAL COIINTER
ASSEMBLY
A15 A16
2-19.
The
5
MHz decimal counter operates
in
a man-
ner similar to the lowfrequency
counter
described in
Paragraph
2-76.
The
circuits
have been
modified by
the use
of:
a) high frequency
transistorsl
b)
reduced
time
constants
inthe interstage couplingnetwork;
and
c) steering
diodes.
The
input
circuit
to binary
A in-
cludes
steering diodes CRg, CR10, CR20,
and CR21.
These diodes gate the
input pulse so that
it
is
applied
only
to
the conducting
transistor. For
example,
if
the
binary
is
in the
"1"
state
(Q1
cut
off,
Q2 conducting),
CRg i
s
reversed biased
b
y
approximately 30 volts
while
CR10
is
slightlyforward biased.
The next input
pulseis therefore steered tothebase of the
conducting
transistor
Q2.
(See
Figure
?-L1.
)
2-80.
50
MHzDECIMAL
COUNTER
ASSEMBLY
A17.
2-81.
GENERAL.
The 50
MHz decimal
counter as-
sembly
is
shown
in
Figure
2-16.
Operation of basic
circuits
isdiscussed inthe Paragraphs listed inTable
2-3.
Circuit details
are given in the schematic dia-
gram,
Figure
7-13.
2-82.
GATED
INPUT.
Five AND gates route the
in-
put signal tothe propertransistorbase for
each
count:
feedback
is
not
used.
Each of these gates
is
labeled
to indicate the results of
an
input pulse
passed
bythat
gate
For
example,
the
first
input pulse
is
passed by
gate
A
(diode
gateA
is
forward biased bythe
negative
collectorvoltage of transistor
A),
This
negativepulse
turns off transistor
A which
turns
on
transistor
A.
In the
same way gate
A
passes
the
second
pulse
turn-
ing
on
transistor
A.
On
counts
2, 4, 6, 8,
and
0
(10)
the
input pulse passed by
gate
A
is
amplified
and ap-
plied to the inputs of gates
B, B,
and
C.
Gate
B
con-
ducts
whenboth
an
input pulse is
present
and
transistor
B is
not
conducting
(this occurs
on counts 2
and
8).
Gate
B
conducts when
both
an
input pulse
is
present
and transistors
B
and
e
are
both turned
off
(this
Area
Paragraph
Reference
Binary circuits
and
counting
logic
Resetting
Electrical
readout
Digitat display
Decimal point
Clipper
diodes
2-25 through 2-29
2-30
2-32
2-33
through
2-35
2-70
2-B
2-t5
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