Sony KV-27EXR25
Started out having an annoying issue where when displaying a Bright
Image (lots of white in the picture) the screen would "neck in" in the
middle of the screen, almost like adding severe pincushion.

Annoying but dealt with it..

Now it has the a blanking issue where the picture will not come up for
5-10 minutes after being turned on. When it does come in, it blinks
in top/bottom half of the picture for 20-40 seconds then finally locks
in. Occasionally I notice on quick picture changes, the screen will
drop out for a second. But then comes right back. Still has the
pincushion issue though.

Any good ideas / URL to an FAQ? I'm good with electronics but never
worked on TVs.

Thanks!
Lance

On 28 Sep 2004 20:12:16 -0700, (Lance) wrote:

Sony KV-27EXR25
Started out having an annoying issue where when displaying a Bright
Image (lots of white in the picture) the screen would "neck in" in the
middle of the screen, almost like adding severe pincushion.

Annoying but dealt with it..

Now it has the a blanking issue where the picture will not come up for
5-10 minutes after being turned on. When it does come in, it blinks
in top/bottom half of the picture for 20-40 seconds then finally locks
in. Occasionally I notice on quick picture changes, the screen will
drop out for a second. But then comes right back. Still has the
pincushion issue though.

Any good ideas / URL to an FAQ? I'm good with electronics but never
worked on TVs.

Thanks!
Lance


Have you tried turning up the screen control a little? The picture
will be blanked if the CRT cathode current isn't high enough. As the
CRT ages it's sometimes necessary to readjust the screen control. I
generally adjust it about mid way between where it blanks and where
you start to see retrace lines.
Andy Cuffe

May be a weak CRT, beam current no longer able to supply needed flow at
specific brightness levels. AKB circuit not able to compensate for the
changes in CRT demands when going from the dark images to the bright. ETC,
there are many issues mostly all related to the supplies and control
circuits for the video output devices and CRT specifically. Including the G2
supply. Agree with Andy's post about advancing the Screen Bias a bit to see
what effect you get, then troubleshoot the symptom, posting results of your
in-depth diagnostics.
"Andy Cuffe" wrote in message
...
On 28 Sep 2004 20:12:16 -0700, (Lance) wrote:

Sony KV-27EXR25
Started out having an annoying issue where when displaying a Bright
Image (lots of white in the picture) the screen would "neck in" in the
middle of the screen, almost like adding severe pincushion.

Annoying but dealt with it..

Now it has the a blanking issue where the picture will not come up for
5-10 minutes after being turned on. When it does come in, it blinks
in top/bottom half of the picture for 20-40 seconds then finally locks
in. Occasionally I notice on quick picture changes, the screen will
drop out for a second. But then comes right back. Still has the
pincushion issue though.

Any good ideas / URL to an FAQ? I'm good with electronics but never
worked on TVs.

Thanks!
Lance


Have you tried turning up the screen control a little? The picture
will be blanked if the CRT cathode current isn't high enough. As the
CRT ages it's sometimes necessary to readjust the screen control. I
generally adjust it about mid way between where it blanks and where
you start to see retrace lines.
Andy Cuffe

Okay, being a 27" then i assume it's not a widescreen, but my recent
experiences MAY apply anyway...

Seems with the early widescreens they weren't all that good at manufacturing
the tubes and they are prone to cathode to gnd shorts (and probably other
kinds of failures).

Symptoms on my set were every now and again the picture would pincushion,
accompanied by a full green raster like you'd shorted the green drive
transistor on the neck board (assuming this TV has one, i'm comparing that
to a Hantarex MTC900/E!) and then the set would shut itself down and you'd
have to leave it off for a considerable amount of time before it would come
back on. Initially hours, then days. Problem happened once in a blue moon
(maybe once in six months), then more often, then to the point of not being
able to use the set.

I did some investigation and found out about the short. At the time i had no
tube rejeuvenator so it had to go to a repair shop. They didn't either
unbeleivably, so they condemned the set. Irony of it was that a friend lent
me a rejeuvenator about two months later. I also found out about a mod where
in theory you could isolate the guns from ground and run a seperate
transformer for them (or something like that), but they weren't prepared to
do that, and TBH, i wasn't too keen either!!

Anyway that was just before xmas two years ago (timing eh!?), fast forward
to last week and me mates Sony had to go in to be looked at for
pincushioning and a very green picture with raster visible (although not
shutting down). Guess what? Tube needed a shot on the rejeuvenator. This
time (i've since moved) we've found a repair shop of the old kind. Lovely
old guy in a lab coat. Prepared to try all the old methods before condeming
and trying to pursuade you to buy a new set and to top it all, first time he
looked at it it only lasted a couple weeks, then went wrong again so when me
mate popped it back he absolutely insisted that if he hoes a job, he does it
right or not at all, and thus refused to accept payment (although a nominal
fee was given to him anyway as this approach is so damn refreshing these
days!).

Admittedly that set is now on last chance saloon as it won't survive a third
shot on the rejeuvenator!

Anyway, this long post was really to demonstrate that Sony TVs of a
particular age (don't know how old this KV-27EXR25 is) were definately very
prone to crt failure. Particularly true of the early widescreens.

Have to say, it's put me off wasting my money on Sony for life. Together
with a Sony video that lasted three years.

Martin.



"Art" wrote in message
...
May be a weak CRT, beam current no longer able to supply needed flow at
specific brightness levels. AKB circuit not able to compensate for the
changes in CRT demands when going from the dark images to the bright. ETC,
there are many issues mostly all related to the supplies and control
circuits for the video output devices and CRT specifically. Including the
G2 supply. Agree with Andy's post about advancing the Screen Bias a bit to
see what effect you get, then troubleshoot the symptom, posting results of
your in-depth diagnostics.
"Andy Cuffe" wrote in message
...
On 28 Sep 2004 20:12:16 -0700, (Lance) wrote:

Sony KV-27EXR25
Started out having an annoying issue where when displaying a Bright
Image (lots of white in the picture) the screen would "neck in" in the
middle of the screen, almost like adding severe pincushion.

Annoying but dealt with it..

Now it has the a blanking issue where the picture will not come up for
5-10 minutes after being turned on. When it does come in, it blinks
in top/bottom half of the picture for 20-40 seconds then finally locks
in. Occasionally I notice on quick picture changes, the screen will
drop out for a second. But then comes right back. Still has the
pincushion issue though.

Any good ideas / URL to an FAQ? I'm good with electronics but never
worked on TVs.

Thanks!
Lance


Have you tried turning up the screen control a little? The picture
will be blanked if the CRT cathode current isn't high enough. As the
CRT ages it's sometimes necessary to readjust the screen control. I
generally adjust it about mid way between where it blanks and where
you start to see retrace lines.
Andy Cuffe

On 28 Sep 2004 20:12:16 -0700, (Lance) wrote:

Sony KV-27EXR25
Started out having an annoying issue where when displaying a Bright
Image (lots of white in the picture) the screen would "neck in" in the
middle of the screen, almost like adding severe pincushion.

Annoying but dealt with it..

Now it has the a blanking issue where the picture will not come up for
5-10 minutes after being turned on. When it does come in, it blinks
in top/bottom half of the picture for 20-40 seconds then finally locks
in. Occasionally I notice on quick picture changes, the screen will
drop out for a second. But then comes right back. Still has the
pincushion issue though.

Any good ideas / URL to an FAQ? I'm good with electronics but never
worked on TVs.

Thanks!
Lance

A couple of things i've heard with the kv-27exr25:

pincushion issue may be a bad pin return coil, supposedly a common
problem. Bad news, if you let it go it screws up other things (pin
amp circuits).

Other common problem is the STR-S6301 voltage regulator. Replacing it
may solve a lot of problems.

Since they're about 13 years old, it may be a good time to get a new
TV. 27" models are flat screen, component video input, and cheap
these days.

Not sure what sony service centers charge to fix a TV these days.

Anyone know what a pin return coil repair would cost ?

Any chance at getting a hint as to where or what the "screen control"
pot looks like?

I have a diagram of the major components in this TV but no mention of
a "Screen" anything... Focus, H Stat, V Stat, AGC...but no "Screen"

Would it be near the flyback?

Boy does time fly, the date inside the TV is 1991.

Thanks.

Andy Cuffe wrote in message . ..
On 28 Sep 2004 20:12:16 -0700, (Lance) wrote:

Sony KV-27EXR25
Started out having an annoying issue where when displaying a Bright
Image (lots of white in the picture) the screen would "neck in" in the
middle of the screen, almost like adding severe pincushion.

Annoying but dealt with it..

Now it has the a blanking issue where the picture will not come up for
5-10 minutes after being turned on. When it does come in, it blinks
in top/bottom half of the picture for 20-40 seconds then finally locks
in. Occasionally I notice on quick picture changes, the screen will
drop out for a second. But then comes right back. Still has the
pincushion issue though.

Any good ideas / URL to an FAQ? I'm good with electronics but never
worked on TVs.

Thanks!
Lance


Have you tried turning up the screen control a little? The picture
will be blanked if the CRT cathode current isn't high enough. As the
CRT ages it's sometimes necessary to readjust the screen control. I
generally adjust it about mid way between where it blanks and where
you start to see retrace lines.
Andy Cuffe

On 4 Oct 2004 17:49:49 -0700, (Lance) wrote:

Any chance at getting a hint as to where or what the "screen control"
pot looks like?

I have a diagram of the major components in this TV but no mention of
a "Screen" anything... Focus, H Stat, V Stat, AGC...but no "Screen"

Would it be near the flyback?

Boy does time fly, the date inside the TV is 1991.

Thanks.



On a Sony TV it's usually located on the little circuit board on the
end of the picture tube. It will be labeled either screen, or G2.
Andy Cuffe

Andy, thank you...

Ok so I FINALLY found the little pot. Turning it up helps the issue
"a little" bit. The screen comes in now after only a 5 minute
delay...but still blinks out on fast transitions dark/light. Also,
now when fed from a good (hot?) signal source like a DVD, the REDs of
the image seem over blown and smeared. But only some times and don't
notice it when using an antenna.

Exactly what did that little pot turn up? I think what it controls
must be weak because the pot is now turned all the way up (was only
1/2 turn from max from factory) and I still don't see the "scan lines"
from being over driven as described by someone else.

Could this and the pin cushioning on bright images be linked to the
same thing, like a weak capacitor issue. If I'm going to need a
service manual I do believe I'll look into a new TV for Christmas...

Thank you for any help and all the help thus far.


-----
Lance


Andy Cuffe wrote in message . ..
On 4 Oct 2004 17:49:49 -0700, (Lance) wrote:

Any chance at getting a hint as to where or what the "screen control"
pot looks like?

I have a diagram of the major components in this TV but no mention of
a "Screen" anything... Focus, H Stat, V Stat, AGC...but no "Screen"

Would it be near the flyback?

Boy does time fly, the date inside the TV is 1991.

Thanks.



On a Sony TV it's usually located on the little circuit board on the
end of the picture tube. It will be labeled either screen, or G2.
Andy Cuffe