HP 5245L Service Manual

Model
5245L
e. Switches +1?0
volts
as first
step
in
generating
lamp
control
voltages
(distinguishes
between CHECK
and
not-CHECK
positions).
Further
srvitching is done
by
A3, final
svitching by
A2.
2-53.
The
level
control
designated
-LEVEL+
on the
front
panel
adjusts the dc
input
trigger level
from
-0.
3 volts dc
to +0.3
volts dc. Refer
to schematic
diagram
Figure
7-3 and
7-4
for circuit details.
This control
allows
the trigger
level
for input
signals
to
be
adjusted above or
below
ground
potential.
The
level
control range
is increased
to
t3
volts
dc when
the input
sensitivity
switch is
set
at 1 volt
rms,
and
is
increased
to
+30
volts dc
for the
10
volt
rms setting.
The
murimum
countercloclsvise
position
(PRESET)
closes
a switch
which
automatically
sets
the trigger
level
at
ground
potential
for
all
attenuator
positions.
2.54.
TIME-BASE
SwITCH
ASSEMBLY
A2.
2-55.
The
time-base
switch
assembly
(designated
TIME-BASE
on front
panel)
is a
lO-position
switch
(EXT,
10s,
ls,
.
1s, 10ms,
lms,
.
1ms, 10ps, 1ps,
.
1ps).
Refer
to the
schematic
diagram, Figure 7-4,
for
cir-
cuit details.
Srpitch functions
are
listed
belorv.
a.
Produces
gate
controls
4,
2tr 22r
23r 24r 25r26,
27, 28,
and 29
using
switched
-15
volts from
A1
(SENSITIVITY
switch).
b.
Produces
all decimal
point
control
voltages
using
switched +1?0
volts
from
A3
(FUNCTION
switch).
Decimal
point
control
voltages
are connected
to appro-
priate
input
terminals
on
decimal
point
assembly
A8.
c. Produces
aII measurement
units
control voltages
using
switched +1?0volts
from
A3. Measurement
unit
control
voltages
are
connected
to
appropriate input
terminals
on measurement
units
assembly
A9.
d. Generates
resetpulsesby
momentarily
supplying
-15 volts
while switch is
between
detent
positions.
This
resets
all counter
circuits
if
time-base
selection is
changed
during
a measurement
operation.
Reset
out-
put
is
connected
to manual
reset
input
of
sampling
control
assembly
(pin
9 of
A23).
e. Connects
time-base
selected frequency from A21
(function
control assembly)
to
EXT
connector
on front
panel
when switch
is
not
in
EXT
position.
Disconnects
selected frequency
from
EXT
connector
when
switch
is
in
EXT
position.
2.56.
FUNCTION
SWTTCH
ASSEMBLY
A3.
2-57. The
function
switch
assembly
(designated
FIJNCTION
on
the
front
panel)
is a
1O-position
switch
(MANUAL
STOP;
MANUAL
START;
FREQUENCY;
PERIOD
A\TERAGE
for
1,
10,
100, lK, 10K,
and 100K
periods;
and REMOTE
OR
TIME II.{T).
Refer
to
the
schematic
diagram,
Figure
7-5,
for
circuit details.
Switch
functions
are listed
belorv.
02349-1
Section
II
Paragraphs
2-53
to 2-bg
a. Produces
gate
controls
?
through
13
by
switch-
ing
-15
volts from
po\r/er
supply.
b. Contributes
to
generationof
gate
controls
1 thru
6
and
21
thru 29.
c. Contributes
to
generation
of
decimal
point
and
measurement
units controls
from
switched +170
volts
from
A1
(SENSITIVITY
switch).
d.
Produces
start
and
stop
input
voltages
(-
15
volts)
to
gate
flip-flop
in
the
gate
control
assembly
(pins
13
and 14 of
A23)
when
switched
to
MANUAL START
and
MAI.{UAL
STOP.
e.
Shorts sample-rate
trigger
pulse
to
ground
at
pin
4 of
A23
when
switched
to
either
MANUAL
START
or MANUAL STOP.
This inhibits
operation of the
sample
rate
and
holdoff
multivibrators,
thereby
pre-
ventingthe reset
amplifier
from
operating
in MANUAL
functions.
This arrangement
allows
the accumulation
of counts in
the
DCA's over
several
gate
openings
during
MANUAL
operation.
Reset
is
still
possible
in
the MANUAL
function by use of
the RESET
push
button on
the front
panel.
f. Opens
thetransfer-pulse
linebetween
the
STOR-
AGE switch on
the
rear
panel
and
the decimal counters
when
switched to
either
MANUAL
START
or
MANUAL
STOP. This
prevents
display
storage operation.
g.
Opens
inhibit-signal line
between
the
DIGITAL
RECORDER
connector
on
the rear
panel
and
pin
12
of A23
when
switched
to either
MANUAL
START or
MANUAL
STOP. This
prevents
undesired
triggering
of
the
holdoff
multivibrator
which could
inhibit
the
gate
flip-flop.
h.
Generates
reset
pulses
by momentarily supply-
ing
-l5volts
while
switch
is
between
detent
positions.
This resets
all
counter
circuits
if function
selection
is changed
during
a
measurement operation. Reset
output
is connected
to
manual reset input of
sampling
control
assembly
(pin
9
of A23).
2.58.
MODE
S\MITCH ASSEMBLY A4.
2-59.
The mode
switch assembly
(designated
MODE
on rear
panel)
is a
three-position
switch
(EXT
STD
FREQ
1
MHz,
INT
STD
FREQ,
SCALER).
Refer to
the schematic diagram,
Figure
7-6,
for circuit de-
tails.
Switch functions are
listed
below:
a. Connects
external 1-MHz standard to trigger-
circuit
of the oscillator assembly
(A26)
when
in EXT
STD
FREQ
1
MHz
position.
b. Connects output ofinternal
oscillator to trigger-
circuit of oscillator assemblywhen in INT STD FREQ
position.
2-13

HP 5245L Specifications

General

Brand	HP
Model	5245L
Category	Cash Counter
Language	English