Date : 10/02/98 R7621127
Sync+Vertical Deflection
R7621127
22
Technical description
- the slider voltage of P1.
The slider voltage is limited both sides with R77 / R87. The user / service engineer
can only determine the high or low freq. mode in some window, the mid range of
frequencies.
As is discussed in the UN HOR DEFL board the two parts of the scan coil windings
are in series in the
lower freq mode
range and in parallel in the "
higher freq mod"
.
The "H FREQ MODE" voltage is obviously sent to the deflection circuits to activate
the relays.
Since the flyback time in the second range is half the flyback time of the lower range
the microprocessor must be informed on the actual range the projector is running.
The
"H FM"
is consequently sent to the microprocessor - controller board.
The
TRACKING HOR FREQ
in the schematics, is proportional with the line
frequency and will be used to track some waveforms with the line frequency.
e) Line flyback pulse simulation
The phase of the
HS
squarewave output, pin 4 of the TDA2595, is determined by the
position of the pulse applied to pin 2
(LFP)
. Delaying this pulse with respect to the
drive pulse of pin 4 will mean that the drive pulse will be shifted back in the time for
about the same amount of the delay.
The width of this pulse also is the width of the SC (Sandcastle) which exits at pin 6.
This pulse is generated by means of two one-shots in IC7. The first one generates
a pulse starting at the end of the scan (= positive transition of the squarewave) and
with a duration determined by the time constant of the one- shot. This duration is
relevant for the delay.
The second one-shot is triggered at the negative transient of the first pulse thus the
output pulse starts with the end of the first pulse. The duration of this pulse will be
the duration of the SC pulse.
As the
TRACKING HOR FREQ
voltage is not at the correct dc level, nor has the
correct range (efficiency), the voltage is put to a suitable range with an OPAMP and
Q5 in the feedback loop. The output is dropped with Z1 and drives simultaneously Q11
and Q9. The delay, this is the width of the output pulse at pin 6 of the one shot in IC4,
is regulated by Q9.
The width of the pulse at output pin 10 is regulated with Q11.
f) Phase alignment :
The HOSC squarewave is not suitable for driving the MOSFETs in the horizontal
deflection. Two one shots will derive a drive pulse with the correct width and position
by means of an adjustable delay (=phase) with respect to the (reference) input sync
signal.
The adjustment range over the entire frequency range must be proportional with the
line period.
The range in
absolute
value must be much lower for the higher frequencies than
for the lower frequencies. The
relative
value (percentage) must be the same. This
is obtained by tracking the phase range with the line frequency by means of an
automatic system (feedback) as described hereafter.
The
PH CONTR"
voltage from the BELLA IC401 on the subunit is sent via R405 to
contact 8 of the J402 connector. The optional ORBITING module can here overrule
the PH CONTR if the projector is switched as a SLAVE.
Summary of Contents for GRAPHICS 1209S
Page 4: ...BARCO PROJECTION SYSTEMS GRAPHICS 1209S 90 00972 230V AC 90 00977 120V AC SAFETY NOTICE...
Page 9: ...BARCO PROJECTION SYSTEMS GRAPHICS 1209S 90 00972 230V AC 90 00977 120V AC GENERAL INFORMATION...
Page 28: ...BARCO PROJECTION SYSTEMS GRAPHICS 1209S 90 00972 230V AC 90 00977 120V AC SERVICE SHEETS...
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