57
PM3394, FLUKE & PHILIPS
ch2
ch1
CH1! 200mV~
CH2! 100 V= MTB10.0us H xx
1
2
T
c h2
c h1
C H 1 ! 20 0 m V ~
C H 2 ! 10 0 V = M T B 1 0 .0 us H xx
1
2
T
DQP Circuit Corner Focus Correction
Focus at the sides of a Wega flat screen picture tube was accomplished
with the Dynamic Focus Circuitry. Focus at the corners is corrected using
a Dynamic Quadrapole circuit. Although they are independent circuits, a
failure in one will make it appear as if the other is also defective. There-
fore, both the Dynamic Focus and DPQ circuits must be tested when
there is poor focus on a portion of the screen. The DQP circuit is also
used to correct for mis-convergence at the perimeter.
Circuitry
IC5511 manufactures the corner focus correction signal that is amplified
and applied to four coils placed at the neck of the CRT. There are two
signals marked Para 1 and Para 2 that output IC5511/pins 4 and 6. They
are amplified and applied to the four QP coils.
At power ON, Q5008 and Q5505 use C5027 to momentary disable the
DQP amplification in IC5504. This is so the beam will be unaffected by
incorrect voltages at start up.
Q5502, Q5507 and IC5502 monitor the horizontal width (AFC-PLS from
Q5030) and corrects for focus if the width changes momentarily. This is
accomplished by changing the DC input voltage of IC5504/pin 2 propor-
tional to the width of the picture.
The waveforms in the following scope shot are made by IC5511/pin 4 and
applied to the QP coils at CN5509/pin 6.
DQP-- Signal Processing
Channel
Name
Location
Voltage
1
DQP negative signal
IC5511/pin 4
0.4Vp-p
2
Amplified DQP- signal
CN5509/pin 6
130Vp-p
Time base = 10usec/div
The waveforms in the following scope shot are made by IC5511/pin 6 and
applied to the QP coils at CN5509/pin 4.
DQP-- Signal Processing
Channel
Name
Location
Voltage
1
DQP positive signal
IC5511/pin 6
0.4Vp-p
2
Amplified DQP + signal
CN5509/pin 4
300Vp-p
Time base = 10usec/div
By comparing both output waveforms, we can see the resultant DQP cor-
rection signal (difference of the two waveforms) is not that complex.
Содержание KV-32XBR400
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