When a commercial comes on that has a large white background.. my tv
will make a buzzing sound and the picture will distort a bit. As soon
as the scene changes to something with more color it stops? Whats
wrong?

Herat:
There might be nothing wrong with your TV..... does it happen on ALL
channels?
Do you have CABLE, Satellite, Antenna???
Does your TV have the same problems with a video tape or dvd?
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


"Herat" wrote in message
om...
When a commercial comes on that has a large white background.. my tv
will make a buzzing sound and the picture will distort a bit. As soon
as the scene changes to something with more color it stops? Whats
wrong?

Herat:
There might be nothing wrong with your TV..... does it happen on ALL
channels?
Do you have CABLE, Satellite, Antenna???
Does your TV have the same problems with a video tape or dvd?
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


"Herat" wrote in message
om...
When a commercial comes on that has a large white background.. my tv
will make a buzzing sound and the picture will distort a bit. As soon
as the scene changes to something with more color it stops? Whats
wrong?

It may be normal; some TVs do an imperfect job of separating video from
audio. The signal coming into the TV may be a bit too strong, if it's cable
or a strong local station.

"Herat" wrote in message
om...
When a commercial comes on that has a large white background.. my tv
will make a buzzing sound and the picture will distort a bit. As soon
as the scene changes to something with more color it stops? Whats
wrong?

It may be normal; some TVs do an imperfect job of separating video from
audio. The signal coming into the TV may be a bit too strong, if it's cable
or a strong local station.

"Herat" wrote in message
om...
When a commercial comes on that has a large white background.. my tv
will make a buzzing sound and the picture will distort a bit. As soon
as the scene changes to something with more color it stops? Whats
wrong?

I have cable. Ive never noticed if it was on certain channels or not.
Is it just something im gonna have to live with? Its not a major
problem or anything. Its just slightly annoying sometimes

Thanks

"Herat" wrote in message
m...
I have cable. Ive never noticed if it was on certain channels or not.
Is it just something im gonna have to live with? Its not a major
problem or anything. Its just slightly annoying sometimes

Thanks

If the signal coming in is too strong, I believe there are attenuators you
can put in. As a quick fix, try connecting the 75-ohm cable to the 300-ohm
input, or something like that, in order to get a weaker signal.

I have seen this in many types of TV sets, especialy the lower cost
sets. This type of effect occurs when the there is a very high amount of
picture illumination, and the beam current causes an increased load on
to the high voltage. Because of the high voltage not being able to
supply enough current, it drops, thus the raster size will also change.
At the same time, the horizontal output stage that is supplying the high
voltage and scans, is not able to put out more power. Since the scans
are also part of this circuit, the gain of the scans will go down under
excessive load, thus causing some pin distortion, and may even cause
some lack of width. In areas of the screen where the illumination is a
bit lighter, there may be less of the scan distortion. This will then
cause some bending of the raster at the edges.

The buzz in the sound can be caused, because when all of the above is
going on, the supply voltages from the secondary side of the flyback
transformer will also drop. These voltage sources are rectified to DC
and filtered. They are usually used to operate the IF, tuner, and
pre-audio stages. If these stages are under-supplied, they may get
noisy, and unstable. If there is some noise generation in the video, it
may not be very visible under high brightness conditions, but noise may
be heard in the sound. Under abnormal conditions, the decoupling caps
may not be able to do their best at keeping the noise down in the B+
distribution to the various stages.

One work around is to lower the contrast setting a little. This will
make the picture a bit less punch, but it should reduce this effect.

In the higher end sets, there is more attention given to the design of
the power supply, high voltage supply, and the scan circuits. They use
more extensive feedback techniques for keeping the scans well regulated.
They also use more a complex design to keep the high voltage and main
power supplies more stable under excessive, and rapidly varying load
conditions.

If you go in to any of the large showrooms where there are a lot of TV
sets, one thing you can do is start winding the contrast control up and
down on the set when there are bright scenes on. Take care to observe
the distortions in the picture. What you do not want is to have the
raster changing size, and there to be some loss of sharp beam focus.


--

Jerry G.
======

"Herat" wrote in message
om...
When a commercial comes on that has a large white background.. my tv
will make a buzzing sound and the picture will distort a bit. As soon
as the scene changes to something with more color it stops? Whats
wrong?