Zenith TV 1994 model SM2568S picture compressed

[Jacques Carrier]

Hi fellow techs,

This 1994 25" Zenith TV model SM2568S has a complete picture which
occupies
about 40% of the CRT face plate.The picture is compressed and centered
about
the middle of the screen.(Wide black bar on top and wide black bar on
the bottom)
My coworker has a 1995 27" Zenith TV with the exact same problem.

Sometimes I get the full picture with 2 fine horizontal lines in the
middle.
All the caps around the vertical IC are OK.(ESR OK)The vertical IC
LA7838 has been resoldered.Is there something else I need to check
before I grab the scope?

Best regards,

Jacques

 

[Ken]

Hi fellow techs,

This 1994 25" Zenith TV model SM2568S has a complete picture which
occupies
about 40% of the CRT face plate.The picture is compressed and centered
about
the middle of the screen.(Wide black bar on top and wide black bar on
the bottom)
My coworker has a 1995 27" Zenith TV with the exact same problem.

Sometimes I get the full picture with 2 fine horizontal lines in the
middle.
All the caps around the vertical IC are OK.(ESR OK)The vertical IC
LA7838 has been resoldered.Is there something else I need to check
before I grab the scope?

Best regards,

Jacques

I believe I have the same set, and once encountered the same problem.
Unfortunately I too changed the vertical IC before I discovered a poor
solder joint on one of the caps for that chip. Look REAL close at your
PWB to see if you don't have the same problem.

 

[Jacques Carrier]

Thanks a lot for the tip Ken.

I resoldered all components around the vert. IC and the set is working fine!

Jacques