PV152
2-19
PRO1200 CIRCUIT DESCRIPTION
CIRCUIT DESCRIPTION
These waveforms are carried to the module via connec-
tors J6 / J7 / J8. These connectors carry the split
(clamped) parabolic waveforms at horizontal and verti-
cal frequency and opposite polarity.
Each correction consists of an orthogonal spot correc-
tion
(*X)
and a diagonal spot correction
(*Y).
To facili-
tate the correction a separate center or ‘screen axis’ and
corner ‘screen corners’ is provided.
The 12 Bella’s for these corrections are found on sheet 1
of the schematics. As the waveforms have opposite po-
larity, the supply voltages for these Bella’s are +3.2V and
-1.8V taken from the convergence board.
The “corner” and “axis” corrections are added per color
and then passed on to the power amplifiers. These power
amplifiers are fully integrated hybrid amplifiers supplied
with + / - DYN.
The supply voltages for these amplifiers are
+30V
(+ DYN)
and
- 17V
(- DYN)
.
Output current flows in 150 Ohm damping resistor across
the stigmator coils and a series feedback resistor of 4.7
Ohm. The voltage developed across this resistor is sent
back to the inverting input of the amplifier for stability.
Note that the jumpers J3 and J4 can be removed in
order to isolate the power stages of the astigmatism and
thus to investigate whether an excessive load on the
supply voltages of the whole convergence board is caused
by one of these amplifiers (or caused by another power
amplifier of this convergence module).
809-10451
Technical description ‘CONVERGENCE DRIVER’ module
Introduction
(Page 6-24 to 6-30)
The Surface Mounted Devices (SMD) technology applied
in the driver module makes servicing of the module dif-
ficult and requires correct tools. The description of the
schematics is limited to the essential functions.
Two trigger pulses are generated to trigger the sawtooth
generator and the dynamic boosting of the power sup-
ply of the end stages. The sawtooth waveforms are
clamped to ground level during one part of the scan-
ning (left/right or top/bottom) and adjusted in ampli-
tude for a linear correction on the scan for red and blue
color (except when the “convergence on green “ option
is mounted).
Multipliers produce parabolic waveforms which undergo
the same kind of flow for the non linear corrections. A
combination of the clamped signals, and a modulation
on either a sawtooth or parabola is needed for the cor-
ner convergence. All the waveforms for one color are
summed with an OPAMP and amplified by a DC amplifier
in the OUTPUT module.
Trigger Pulse generation
Pulse 1 and 2
(Page 6-30 Sect. D-4)
The HDR_CONV is speeded up and inverted by Q603. The
negative pulse at the collector triggers monoflops IC9
and IC19.
Pulse 1:
(trigger of the sawtooth generator).
The width of the positive output pulse at pin 13 of IC9
is adjusted with P1. The pulse train at the output pin
13 is integrated with R34/C620 and applied to one in-
put (+) of the OPAMP IC15. The voltage across C620 is
proportional to the width of the pulse and the line fre-
quency. The output of this OPAMP determines the cur-
rent of the current source Q9. This current adjusts the
width of the pulse at the output pin 7 of IC19. The time
constant of this one shot is designed to be a little less
than the time period. That time constant needs to be
tracked with the line frequency and this is realized as
follows. The opposite polarity output pin 7 is integrated
by R677 / C663 and applied to the inverting input of
the same OPAMP.
The pulse at pin 7
(Pulse 1)
starts consequently just
before the end of the scanning and is used to trigger
the horizontal sawtooth generator.
Pulse 2:
(dynamic boosting of power supply).
The pulse output at pin 13 triggers on the positive go-
ing transient the second monoflop in IC9. The width of
the output pulse at pin 5 is adjusted with P2. Through
the buffer Q5 the pulse is available for boosting the
supply voltage of the power end stages. Note that this
pulse 2 is also added via D38 to pulse 1.
Horizontal axis convergence
(Page 6-24 Sect. C-2)
Horizontal sawtooth generator.
C602 is charged by the current source Q2. In order to
stabilize the amplitude the charging current is tracked
with the line frequency as follows. The sawtooth is buff-
ered and an average value of the amplitude is obtained
by integration with IC3 / C7 . The resulting output volt-
age adjusts the charging current of the current source
Q2. The amplitude is set by the voltage at the other
input of the OPAMP, thus by R2 / R602.
The sawtooth is inhibited by the clamper Q22 when the
current consumption of the power end amplifiers is too
big (see Power Output stages).
OPAMP IC3 (5-6-7) amplifies the sawtooth in order to
