Question about Televison & Video
In one 21"color CRT tv vertical linearity is lost suddenly and picture is streched from upper side and compressed from bottom side (no rolling and we can see the movie but streched.
In vertical section preset could not change the error.Vertical IC 7830.
I replaced 1000Uf and 220 UF capacitors with new one but didnt solve.(i donthave oscilloscope )what can i do now.Thanks in advance
Vertical linearity is more of a DCV bias issue rather than feedback or AC coupling. Hence it would be more apt to suspect resistors rather than capacitors. Of course, it is also possible that the large IC that drives the Vertical output maybe at fault (least likely) but often would have trimpots for adjustment. Most current designs do away with trimpots and rely on self correcting (feedback loop) which is simply a resistor in the 100k range. In certain instances, it could be a thermistor or resistor or diode limiter attached to the yoke itself.
Best would be to use a service manual or at the very least a schematic diagram with voltage readings and compare actual on PCB against schematic.
If you could post back the make & model or preferably the chassis number of the TV, might be able to comment back known common vertical issues.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
Good luck and kind regards.
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Posted on Jun 06, 2008
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Posted on Jan 02, 2017
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