Sony KV-13FS100 Product & Training Manual page 32

IK Pulse Waveform Diagrams
NOTE: Waveforms 6-4, 6-5, 6-6, 6-7, and 6-8 are a sequence of pictures illustrating where the IK are found, and
how they appear on an oscilloscope display. Reference these Waveforms during the following IK_AKB circuit
description. Note: Use IC545/pin 3 to trigger oscilloscope and lock signal on the display. All oscilloscope settings
are where taken using a X10 probe
The Waveform sequence description is as follows:
1) Waveform 6-4 shows the oscilloscope time-base starting point at the field rate. The IK pulse and IK
Feedback pulses occur during the vertical blanking areas. These areas are shown as gaps between each
field.
2) Waveform 6-5 is an expanded view of Waveform 6-4 showing one field and one vertical blanking area.
3) Waveform 6-6 is an expanded view of Waveform 6-4 showing the IK pulses to the CRT's from IC001/pins
31, 33, and 35. These pulses are located in the vertical blanking area just before active video. Two
consecutive pulses at a flat video level (or brightness level) can be seen.
4) Waveform 6-7 is a further expansion of Waveform 6-4, showing the IK Feedback pulses (IC1751/pin 5) in
the vertical blanking area just before active video (one field). Three small consecutive IK feedback pulses
can be seen.
5) Waveform 6-8 is a close-up shot of the IK feedback pulses.
Also shown in Figures 6-2 and 6-3 is the IK_AKB signal path. The purpose of the IK signal and AKB circuit is to
monitor and adjust the cathode bias on CRT's (Red, Green and Blue) for optimal white balance. The IK pulses
are output from IC001/pins 31, 33 and 35 (RGB Drive signals) initially when the unit is turned ON, and then
repeated for each field thereafter (reference Waveform 6-6). The pulses are output during the over-scan (or
vertical blanking) portion of the picture, so they are not visible on the picture tube. The IK pulses are shown in
Waveform 6-6 as two flat video levels just before active video. These pulses are sent to their respective color
cathode in a staggered order with red first, then green and blue to drive the tube at a flat raster level. They follow
the same path as the RGB signal described in the previous paragraph.
Once the IK cathode drive pulses are applied to each color cathode in sequence (red-green-blue), IC1751/pin 5
outputs a corresponding IK Feedback pulse proportional to the current draw of each cathode (feedback pulses
shown in Waveform 6-7). The IK feedback pulses are sent through CN1752/pin 2 and applied to buffer transistor
Q301. After buffer Q301, the IK feedback pulses are input to IC001/pin 51 and evaluated by the internal AKB
circuit. The AKB circuit determines if the drive to the cathodes needs to be adjusted for optimal white balance, or
if one of the CRT's is defective (No feedback pulse). The IK-AKB input IC001/pin 51 is also level protected using
D351 (3.3V).
Location of IK pulses just before active video on each field
Oscilloscope
Settings:
0.2V
5 s
µ
Horizontal Field & Vertical Blanking (IC001/Pins 31, 33 & 35)
Waveform 6-4
Oscilloscope
Settings:
0.2V
5 s
µ
30
6. Video/RGB
Location of IK Pulses just before active video.
One Horizontal Field and Vertical Blanking
(IC001/Pins 31, 33 & 35)
Waveform 6-5