Commodore 1084S-P1 - Electrical Settings; Chassis Settings; VG2, Cut-off Points, and White D Settings; Focusing Adjustment

CAUTION
1)
Safety
requirements
stipulate
that,
during
repair,
the
set
shouid
be
restored
in
its
original
state
and
that
parts,
indentical
to
the
specified
ones,
should
be
applied.
2) For safety reasons, the parts provided with the sign
should be replaced by identical parts (for code
numbers see electrical parts lists.
3) To avoid damages to ICs and transistors, flash-over
of the high-tension should be avoided.
4) Be careful when performing measurements in the
high-tension section and on the picture tube.
5) Never change parts when the set is still switched on.
6) Safety goggles must be worn during replacement of
the picture tube.
ELECTRICAL SETTINGS
1. SETTINGS ON THE CHASSIS
1.1 +128V supply voltage(3414)
- Apply video signal to the monitor.
- Set volume control 3295, brightness contro! 3662 and
contrast control 3658 to minimum.
- Set trimrhing potentiometer 3414 in mid—position.
(This is a presetting).
- Connect DC voitmeter to junction of resistor 3520 and
diode 6453.
~- Switch on monitor.
~ With trimming potentiometer 3414 set the DC voltage
at junction 3524/6453 to 128V.
1.2 Horizontalsynchronisation (3257)
- Apply video signal (cross—hatcn pattern) to the monitor.
- Short capacitor 2270. (This capacitor is connected to
pin 5 of IC 7270.)
- With trimming potentiometer 3257 adjust the picture
so that it is straight.
- Remove the short-circuit on 2270.
1.3 Picture positionsettings
General: For the following settings apply a video signal
(cross—hatch pattern) to the monitor.
1.3.1 East-west correction (3537)
- With potentiometer 3537 make the vertical lines on the
left and right-hand side of the screen as straight as
possible.
1.3.2 Picture width (3534)
- With potentiometer 3534 set the picture width for 14
blocks to 260 mm.
1.3.3 Horizontal picture centering (3264)
- With potentiometer 3264 set the correct horizontal
centering.
1.3.4 Vertical picture centering (3583)
- With potentiometer 3583 set the correct vertical
picture centering.
1.3.5 Picture height (3550)
- With potentiometer 3550 set the picture height for 10
blocks to 186 mm.
1.3.6. Vertical linearity (3573)
- Adjust the correct vertical linearity with Pre-set
potentiometer 3573 IF necessary repeat 1.3.5 and
1.3.6.
1084S-P1 SERVICE MANUAL
1.4 Setting of:
®@ VG2 (bottom knob on the line output transformer)
®
cut-off
points
of
the
picture
tube
(3107,
3117
and
3127)
® white "D” (3671, 3680)
- Set the brightness to 1/4 of its range and set the
contrast to minimum.
~ Set the potentiometers 3107, 3117, 3127, 3671 and
3680 in mechanical mid-position.
- Set VG2 potentiometer to minimum.
~- Set the signal generator in “pur” position and
introduce the respective colours red, green and blue.
- Using potentiometers 3107, 3117 and 3127 with the
corresponding colour pattern, set the voltage on the
picture tube pins 8, 6 and 11 to 100V.
- Apply a white frame and adjust the VG2 potentiometer
so that any colour among red, green or blue becomes
visible.
- Set the pattern generator to purity with the colour that
was first visible.
- Reset VG2 potentiometer to just visible light.
- Adjust the two remaining colours with their
corresponding purity colour to the same light output
using potentiometers 3107, 3117 or 3127.
- Return the signal generator to white frame and adjust
the potentiometers 3107, 3117 and 3127 so that an
optimum background colour is obtained.
- Using potentiometers 3671 and 3680 (with white
frame) adjust the background colour so that at
minimum brightness and maximum brightness the
background colour is the same.
1.5 Focusing (top knob on line outputtransformer)
- Apply white pattern to monitor.
- Adjust focusing so that the picture at 2/3 of the
diagonal lines (counting from center to four corners)
of the displayed screen is as sharp as possible.
1.6 Subcarrier oscillator(2613)
— Apply colour bar pattern to monitor.
- Connect 4700 resistor between point 11 of IC 7610
and earth.
- Adjust 2613 so that the colour picture on the screen is
stationary.
— Remove the 470Q resistor.
1.7 PAL delay line (3619, 5632)
- Apply DEM pattern from a pattern generator to the
monitor.
- Set brightness control 3662, contrast control 3658 and
colour saturation control 3654 to 3/4 of the range.
- Adjust 3619 so that the "venetian blinds” in the third
bar disappear.
- Then adjust 5632 until the "venetian blinds” in the first
and fourth bar disappear.
- Readjust 3619 as described above.
1.8 Chrominance suppression(5605)
- Apply colour bar pattern to the monitor.
~ Connect oscilloscope to pin 15 of IC 7640.
~- Set 5605 so that the chrominance signal is minimum.
(The chrominance signal is superimposed on the grey
steps of the luminance signal).
1.9 Audio balance (3298)
- Apply sinusoidal signal of 177mVrms (1KHz) to both
audio inputs L/R.
- Set volume control in mid-position.
- Replace the two loudspeakers with a 16Q resistor.
- Set 3298 so that the output level on both 16Q
resistors.is the same. eee