Help needed troubleshooting Sony KV-25XBR TV

[Bearcat]

OK, I know it's an old set, but I'm trying to keep it alive until the
digital sets drop to a reasonable price - besides, I have another set
for parts and the service manual, what I lack is trouble shooting
experience. The problem seems to come and go at short intervals, the
picture's colors are completely off - white text is black, the picture
is a lot darker than it should be, skin colors are very red. Here's a
link to a couple of pictures from a digital camera, one that's good,
and one that's bad. I probably should have paused the source so the
input was identical, but I didn't think of that until just now. The
service manual has a lot of good detail, but with no real experience
troubleshooting tv's, I'm betting there's someone out there that can
take one look at these pictures and say "Oh, there's problem abc with
the xyz circuitry" that I can then find the details of in the service
manual and track down the problem. Given the sheer number of discrete
components in this set, odds are it's something that a new part and a
few minutes with a soldering iron would fix.

http://f1.pg.photos.yahoo.com/ph/[email protected]/album?.dir=/21c9

I've read the repair FAQ and the problem comes and goes very quickly,
no "fading" in and out of the problem, so I'm hopefull that it's not
just a bad CRT. At the same time I don't know enough about colors to
be able to say "It's full on red" (that doesn't seem to be the case,
otherwise why white text goes full black?)

Please take a quick look at the pictures and get me going in the right
direction!

Thanks!!

 

[RonKZ650]

Yahoo won't let me look at the pictures, but the main problem that causes your
symptoms is bad solder connections. As you are looking from the back of the
set, the board to your farthest left is the video board. Look for any
rectangular shaped parts that solder to the board with about 5 solder
connections. This is generally the problem. The KV25XBR is not an easy design,
good luck. At least it's *really light to carry* a *portable* Well maybe not

Ron

 

[Jerry G.]

I agree with you 100%. This is an older model, and it is also a very
complex set to troubleshoot. Considering the age of this set, there may be
many parts that are getting warn down. I think this set must be about 20
years now. I think they came out around 1984 to 1986. It is one of the first
XBR sets made!

--

Greetings,

Jerry G.
=====


Yahoo won't let me look at the pictures, but the main problem that causes
your
symptoms is bad solder connections. As you are looking from the back of the
set, the board to your farthest left is the video board. Look for any
rectangular shaped parts that solder to the board with about 5 solder
connections. This is generally the problem. The KV25XBR is not an easy
design,
good luck. At least it's *really light to carry* a *portable* Well maybe not

Ron

 

[Jerry G.]

You better find a better way to display your photos. The general people here
do not have a password to look at your pictures!

The message displayed is:

The File You Are Looking For Is Inaccessible.

Please sign in and try again or check with the owner of the file.



Going by your description, and lack of experience, the logical thing to do
would be to have someone that is experienced with Sony sets to troubleshoot
it for you. These sets are fairly complex, and are sometimes a challenge for
the most experienced techs. Many times the small TV service shops will
jobber out their more complex problems to the factory service reps, when
they get a very difficult fault condition, or one that requires a
specialized set-up to work on.

Going by your description, I would check the G2 bias to the CRT, high
voltage section, and the bias voltages to the CRT guns. The original Sony
service schematic should usually give an average value for these. This is
just to start with. I would guess you looked for the possibility of any cold
solder connections.

Your description seems to be one of where the CRT is changing brightness
intermittently. There are many things that can cause this type of fault. It
would be difficult to fix your set "remote control style" over emails.



--

Greetings,

Jerry G.
=====


OK, I know it's an old set, but I'm trying to keep it alive until the
digital sets drop to a reasonable price - besides, I have another set
for parts and the service manual, what I lack is trouble shooting
experience. The problem seems to come and go at short intervals, the
picture's colors are completely off - white text is black, the picture
is a lot darker than it should be, skin colors are very red. Here's a
link to a couple of pictures from a digital camera, one that's good,
and one that's bad. I probably should have paused the source so the
input was identical, but I didn't think of that until just now. The
service manual has a lot of good detail, but with no real experience
troubleshooting tv's, I'm betting there's someone out there that can
take one look at these pictures and say "Oh, there's problem abc with
the xyz circuitry" that I can then find the details of in the service
manual and track down the problem. Given the sheer number of discrete
components in this set, odds are it's something that a new part and a
few minutes with a soldering iron would fix.

http://f1.pg.photos.yahoo.com/ph/[email protected]/album?.dir=/21c9

I've read the repair FAQ and the problem comes and goes very quickly,
no "fading" in and out of the problem, so I'm hopefull that it's not
just a bad CRT. At the same time I don't know enough about colors to
be able to say "It's full on red" (that doesn't seem to be the case,
otherwise why white text goes full black?)

Please take a quick look at the pictures and get me going in the right
direction!

Thanks!!

 

[David]

Read the faq at www.repairfaq.org first. Then if you are completely
sure of what you are doing, look for failed solder connections to the
glass pack delay line in the comb filter circuit and repair the
failing solder connections to the degauss thermister (since you have
it apart and they will be bad if not repaired before).

Unable to view the pictures, but have repaired several of those where
it loses all luminance to the image, you only see the color part of
the picture.

Be aware that it is an old set and the flybacks in the model are prone
to failure with age, if it does fail time ot replace the set as it is
common for the power supply to be damaged when the flyback goes out.

David

 

[Bearcat]

Thanks for everyone's replies, sorry the pictures weren't accessable.
The FAQ has helped me on this set before, I had to replace the HOT and
HV xformer. That was on my 1st of these sets, I actually have 3 of
them now, the 1st I bought new, the other two I picked up from friends
who just happened to have the same set. The one I'm fixing is one of
the ones I picked up, the electrolytic caps in the power supply had
gotten old and it took a long time to power on. I'll check the video
delay line on it. I need to get this set (#2)working as set #1 (#3 is
just for parts - if for no other reason that the case is a hot coral
pink color!) is starting to act up. Just to take advantage of everyone
here, it's sympton is that the picture "collapses" with a rainbow
flash, then reappears just as quickly as it happens. It seems to
happen fairly randomly, no apparent connection to time powered up or
anything. Any ideas on what might be up with it?

Thanks!!

Bearcat