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Originally Posted by roundscreen
Even with weak contrast the k 7 has a nice picture. What was the reason that the ground was missing to the controls? Broken wire or a trace on the board?
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Somebody has removed a ground connection from the tuner board. I have replaced it.
Meanwhile I found the reason for the low contrast. This set works with a shunt regulator and a beam current control: the high voltage coil is connected with the contrast automatic via a diode. When high voltage increases, a negative pulse is given on the grid of the tube for contrast control and keeps the peaks of the video signal low. In this unit, there is a beam current control potentiometer. I have adjusted this potentiometer and so I got full contrast. In the attachment is a screenshot, now with full contrast (correct: with contrast control in middle position).
A convergence failure was also fixed (no horizontal parable voltage and therefore no convergence at both sides of the picture).
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Originally Posted by roundscreen
Are you working on the east German set?
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No. This set belongs to a friend of mine. But he made the photos for me.[/QUOTE]
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Originally Posted by roundscreen
Also why is the 21cyp22 yoke and convergence assembly turned to the left? Vary interesting.
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I think that somebody has disassembled the set and assembled it again without knowing the correct size of the yoke.
Eckhard