Philips PM 3266 - Page 162

167
3.4.16.
Adjustment
of
storage
section
3.4. 16.
1.
INTRODUCTION
The
voltage
levels
that
must be
adjusted
are
indicated
VI
till V8.
These
voltage
levels
are
indicated
in
Fig.
3.29.
for
the
NON
STORE
and
VARIABLE
PERSISTENCE
modes
and
in Fig. 3.30.
for
the
FAST
mode.
The
voltage
levels
can be
measured
with
an
oscilloscope:
when measuring
voltage
levels on
the
front
mesh
take
care
that
the measuring
oscilloscope
and
attenuator probe
can withstand
the 500 Volt
pulses.
3.4.
16.2. NON
STORE
MODE
(MEMOR Y
OFF)
The Collimator
2 voltage
V6
must be adjusted
in the VARIABLE
PERSISTENCE
mode.
3.4. 16.3.
VARIABLE
PERSISTENCE
MODE
1.
Turn
the PERSISTENCE
control
(R16)
fully counter clockwise
so that
the dynamic
erase pulses
on the
front
mesh are
switched
on. Adjust
these pulses to
approx.
+8
Volt by means
of R2423.
Adjust
the storage
level VI
on the front
mesh to 0 Volt by means
of R2577.
Adjust
the
erase
pulse
voltage
V2 on the front mesh
to
+10
Volt
by means of R2427.
2.
Adjust the
voltage on collimator
2 to the lowest
possible value
by means of R2523.
The
borders of
the illuminated
area on the CRT
screen
must
be just invisible.
3. Turn
the PERSISTENCE
control (R16)
to its
first
clockwise stop
(not
in
the MAX position) so that
the
dynamic
erase pulses on
the front mesh are switched
off.
Depress the ERASE
pushbutton
(S25) and
decrease
by means of R2427 the
erase pulse voltage V2 so
that the
CRT screen is just
black.
Repeat this procedure in order to obtain optimum result.
4. In
the MAX WRITE
position the storage
level
is
increased a little and
the
background illumination
on
the CRT
screen
can be adjusted to the desired
value by means of
R2414.
5. The illumination
of
the
left
half and the right half of the CRT screen must be equal. This must
be
adjusted by
means of R2549.
R2549
determines the cathode current of the left and the right flood gun
system.
6.
Adjust
by means of R2404
the pulse voltage V7 on collimator
3
in such
a way that the
background
illumination
over the whole
screen area is divided as equal as possible after the ERASE pushbutton has
been
depressed.
3.4.16.4. FAST MODE
Before
starting
this adjustment the writing gun must be adjusted well in the NON STORE mode.
The adjustment of
the
writing
gun is alright
if:
1.
One cycle of
a
sine wave
signal of 50 MFIz and 6 divisions height can be written in.
2.
The modulation pulse
on G1 of the CRT
during
the writing in cycle is 80 Volt.
When measuring
this take care of dangerous voltages.
3. The defocusing in
horizontal direction
on
the left half and the right half
of the CRT
screen
is
minimal
and symmetrical.
The adjustable
voltages must be adjusted as follows:
1. Adjust voltage
level V2 on the front mesh by means
of R2429
to
+5
Volt.
Adjust
voltage level V3 on
the
front mesh
by means
of
R2419 to 0 Volt.
Adjust voltage level
V4 on the fast mesh by means of R2408 to
+2
Volt.
Adjust
voltage level V5 on the fast
mesh
by means of
R2412
to
+1
Volt.
2. Depress the ERASE pushbutton and check if the CRT screen is
black if
the instrument stands waiting
for writing
in
a
signal. If this
is not the case, voltage level
V3
on
the front
mesh
must
be
decreased
by
R2419 till
the screen is just black.
3. Depress the ERASE
pushbutton and write
one cycle of the 50 MHz/6 div. signal in.
Voltage
level V5 must be decreased
by R2412 if after the transfer
pulse the screen is illuminated with
max. intensity or
if parts
of
the
written in signal are visible on a
background
with
a too high
intensity.
Voltage
level V5 must
be increased if after
the
transfer
pulse the background intensity
is alright and the
written
in signal is hardly visible.