Philips PM 3266 - Page 118

123
The
output
on
D221
7/pin
2 is
the
inverse
of
the
signal
on
D221
1
/pin
3.
After
receiving
a
high
level
on
its
clear
input
(pin
4)
the
flip-flop
D2208
comes
into
the
reset
condition
and
J
Q
output
(pm
1)
becomes
low.
This
results
in
the
input
of
the
100
ms timer
becoming
low
and
C2208
rapidly
output
15 of
D2213
low.
In
turn,
the
500
ms
timer
receives
this
low
input
and
C2209
IS
discharged
via
V2207
and
the
output
of
this
timer
becomes
low.
This
reset
action
is passed
to the
succeeding
timers
in
a similar
manner.
The
D
flip-flop
D2208
receives
a
clear
command
under
the
following
conditions:
a.
If
the
oscilloscope
is
switched
on,
the
circuit
comprising
R2314,
C2231,
V2251
and
inverter
D2217/7,
6
generates
a
positive
pulse for
550
ms.
This
pulse
is
necessary
to
give
certain
flip-flops
in
the
storage
section
a
defined
preset
value
after
switching
on
the
instrument.
D
flip-flop
D2208
received
the
550 ms clear
pulse
on
pin 4
via
diode
V2252.
b. In
the WRITE
mode,
a clear
pulse
comes
1200
ms after
flip-flop
D2208
has
been
set. This pulse
comes
via
D2207/8,
9, 10,
D2207/12,
13,11
and V2205.
c. In the
FAST
mode,
a clear
pulse
comes
1
00 ms after
the
sweep of
the
selected
time-base
has
ended.
This
pulse
is
received
via
02207/5,6,4,
02207/12,13,1
1 and
V2205.
NOT
BUSY
SIGNAL
If the
"not busy"
line (BUSY)
is
low, it
prevents
parts of the
storage
logic from
responding
to
a change in
the
combination
of
the
mode
pushbuttons
S24A,
S24B, S24C. This
line remains
low
if
an erase/prepare
-
write
-
transfer
cycle
is
occurring.
The
"not
busy" signal
comes from
the
inverting
output
(pin
2)
of 0 flip-flop
02208
via diode
V2224.
In the WRITE
mode: for
1200
ms after
tg
the cathode of 02224
is low
and thus
the
"not busy"
line is
also low.
In the
FAST
mode: from
tg until
100 ms after
the end
of the
time-base
sweep the
"not
busy" line is
also low.
ETB
AND BTB
PULSE
GENERA
TOR
The End
of
Time-Base
(ETB)
and
Beginning
of Time-Base
(BTB)
pulse generator
consists
of
02223, a
low-voltage
to high-voltage
translator,
followed
by NANO
gates
02214/5,6,4 and
02214/1,2,3 ANO
gate 02209/1
2,13,1
1,
and inverter
02212/14,15.
The generator
produces
in the FAST
mode an
output
pulse on
02212 pin 15
at the end of
the selected
time-base,
and an
output pulse
on
02209 pin 1
1 at the
beginning of the
selected
time-base.
The generator
is only
operative
in
the
FAST
mode
because pin 1
5 is
made high in
this mode.
If the main
time-base
is selected
for
horizontal
deflection, then
input pin
5
of 02223
is high,
and input
pin
1
1
is low during
the MTB
sweep.
If
the
delayed
time-base is
selected for
horizontal
deflection,
then input
pin
5 of 02223 is
low,
and input pin
12
is low during
the
0TB sweep.
02223
forms
an interface
between
the
time-base logic and
the storage
logic.
The
output
pulses from
02223 are
selected
by the logic
gates and shaped
by the
differentiators
C2227, R2267
(ETB
pulse) and
C2232,
R2243
(BTB
pulse).
At the end of
the
time-base sweep,
a positive
pulse with
a fast risetime
is present
across
R2267; the
negative-
going pulse at
the
start of the
time-base
is not used.
At the beginning
of the
time-base
sweep, a
positive pulse with
a fast risetime
is present
across R2243;
the
negative-going
pulse
at the end of
the time-base
sweep is not
used.
AUTO-ERASE
TIMER
The auto-erase
timer comprises
the
monostable
multivibrator
02227, transistor
V2216 and timing
capacitor
C2217.
In the FAST
mode,
this circuit
generates pulses
with an adjustable
interval
(3
...
8 s). These
pulses have the
same
result
as
the operation
of the ERASE
pushbutton.
The repetition
time of the
pulses is
adjustable with the
VIEW
TIME
potentiometer
R16.
This
potentiometer produces
a voltage
that charges
timing
capacitor
C2217,
which
is
connected to
the trigger
input
(pin
8)
of
the monostable
multivibrator
02227.
The
multivibrator
is
able to trigger
if
pin 6 is made
low; i.e.
in the FAST
mode. If
the
voltage on the
timing
capacitor has
reached
a
certain value,
02227
is triggered
and
produces
a positive
pulse
at output pin 10
for
1
ms. Transistor
V2213
now
becomes
conductive for 1
ms
and gives an
erase
pulse to pin 3 of
0 flip-flop
02208.
Transistor V2216
also
becomes
conductive
and
discharges
timing
capacitor
C2217.