Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Jacques Carrier
 
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Default Zenith TV 1994 model SM2568S picture compressed

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
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Ken
 
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Default

Jacques Carrier wrote:
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.
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Jacques Carrier
 
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Ken wrote in message ...
Jacques Carrier wrote:
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,




Thanks a lot for the tip Ken.

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

Jacques



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.

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