Sony TV KV-32XBR95S,horizontal light bands

[Dan]

My sony XBR is quite old (92 vintage) but still love the great picture.
Recently it developed the problem of horizontal bands of light and dark
across the entire screen which only appear in light scenes. If the picture
is dark, there are no bands and the intensity or how visible the bands are
is in direct proportion to how bright the picture is. It appears that the
bands are a distortion in the vertical sync. Thought it could be a power
supply related problem because of the sensitivity to brightness level. I do
have the service manual for the TV. Any suggestions on where to start
looking would be greatly appreciated.

Thanks in advance,
Dan

 

[James Sweet]

My sony XBR is quite old (92 vintage) but still love the great picture.
Recently it developed the problem of horizontal bands of light and dark
across the entire screen which only appear in light scenes. If the picture
is dark, there are no bands and the intensity or how visible the bands are
is in direct proportion to how bright the picture is. It appears that the
bands are a distortion in the vertical sync. Thought it could be a power
supply related problem because of the sensitivity to brightness level. I do
have the service manual for the TV. Any suggestions on where to start
looking would be greatly appreciated.

Thanks in advance,
Dan

Sounds like a classic case of jailbars, find the capacitor that filters
the B+ to the video amp, usually it's a 250v lytic on the neck board but
I haven't had that symptom on a Sony so it may be elsewhere.

 

[Dan]

James,
Thanks for your quick response. I should point out that the banding seems to
be a function of the horizontal scan lines being either widely separated or
closer together--you can actually see the difference in the width between
the scanning lines as opposed to normal where you can not easily see the
scan lines. That's why I thought it was associated with vertical scan signal
rather than a video problem.
Dan

 

[kip]

That Model is know for many bad filter caps
and a mulitude of bad solder joints .
A heavy weight set worth fixing.

kip

 

[Dan]

Kip
Any suggestions on which filter caps are suspect in this case? Can I test
them with a cap ESR meter that I have?

Dan

 

[kip]

Yes use the ESR meter...also look for swollen caps
in the power sections and around the flyback area.
Caps are cheap ....Go to it.
kip

 

[Skype_man]

May just be bad solder at the vertical IC. Sky.

 

[Dan]

Thanks for all of your suggestions--will have at it and let you know how I
make out

 

[Dan]

Thanks for all of your suggestions--will have at it and let you know how I
make out

 

[Dan]

One last question--TV must have heard that I was about to repair it--is now
working fine. The symptoms normally started a short time after warming up
but then sometimes disappeared. Today no symptoms. Question--is this more
likely a poor solder connection than a bad filter cap. Thought once a cap
went bad it would stay bad.

 

[[email protected]]

Once a cap goes bad it stays bad?
If a capacitor is marginal, in other words just barely outside of
tolerance for ESR and in process of drying out, the temperature will
affect how the capacitor acts in circuit. It is not uncommon for it to
appear to work when it is warmed up when it is just outside of
specification.

That being said, your specific symptom is more than likely solder
connection related. The set will need carefully inspected for bad
solder connections to all the low voltage regulators, the vertical ic,
along with potential solder problems inside the tuner and IF can.

 

[[email protected]]

No, lytics heal sorta when the temp goes up. Many sets in the shop need
a cooldown before we can see a symptom.

If you are indeed seeing rarifications in the scan lines head for the
vertical, and if included, the N-S pincushion ckt or the dynamic
convergence circuit. Of course you are still looking for electrolytics,
most likely.

JURB

 

[Dan]

Actually my symptoms only appear when temp goes up. Always start after set
is on for some time and then may disappear after a time. Never appear when
set is first turned on.

For the past 2 days, no symptoms, even after extended operation but I have
not done anything to fix it.

Once again, thanks for all of your helpful responses. I'm a newbie on this
list and it is the most responsive and helpful list I have ever posted to.