kt
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Oct 30, 2003, 7:07 AM
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Toshiba vertical problem
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 I am working on a Toshiba 27". Have a horizontal line in center of screen with vertical retrace lines above it for about 6". Have replaced vert output IC301, video/vert IC501. Voltages on both IC's are off. The output of IC301 should be 14v, I have 4v. All supply voltages have been checked and are good. Pin 7 should be 1.2v, I have a -.02 or something like that. Voltages on IC501 at the vertical circuit portions are also low. Traced back to vert signal detect transistor, and voltages are good there. I had replaced IC301 previously, but a slip of my probe shorted it and R327. After replacing R327, I had 10v on the output of IC301, but pin 6 only had 14v instead of 27v. The screen then showed a 1.5" band of video with no retrace lines. Concluded I had shorted the IC, so I replaced it again. Now the voltages and appearance of the screen are back to what I started with. Something seems to be bringing down the output of vert IC301 from 14v to 4v, and also bringing down voltages on the vertical circuit pins of IC501 (26, 27, 28), which are connected through resistors to the output of vert output IC301.
Have checked diodes and transistors and they check good.
Any help greatly appreciated.
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