Sharp 28JW-73H - Intermittent Flicker

[Alasdair Campbell]

Hi,

I'm trying to research a fault a friend's TV has. A picture paints a
thousand words, so two shots follow this brief description.

Sharp 28JW-73H / 29JW73H (GA200 Chassis)

After the TV has been turned on for a few minutes a strong green and
yellow flicker appears on all inputs. I will have the opportunity to
preform a visual fault finding investigation in the next couple of days,
but in the meantime does this fault ring any bells with the engineers in
this forum?

The photo shows a bar, but in real-time, the bar is not visible, just a
stomach churning flicker at high freq. There is no vertical rolling
visible either.

I will be able to open up the TV in the next couple of days and check for
obvious faults, and am capable of replacing them, however if anyone
recognises the type of fault straight away I would be glad to glean some
of your wisdom.

best,

Alasdair

Photos:

http://www.alasdaircampbell.com/flicker.jpg
http://www.alasdaircampbell.com/flicker2.jpg

 

[Yukio YANO]

Hi,

I'm trying to research a fault a friend's TV has. A picture paints a
thousand words, so two shots follow this brief description.

Sharp 28JW-73H / 29JW73H (GA200 Chassis)

After the TV has been turned on for a few minutes a strong green and
yellow flicker appears on all inputs. I will have the opportunity to
preform a visual fault finding investigation in the next couple of days,
but in the meantime does this fault ring any bells with the engineers in
this forum?

The photo shows a bar, but in real-time, the bar is not visible, just a
stomach churning flicker at high freq. There is no vertical rolling
visible either.

best,

Alasdair

Photos:

http://www.alasdaircampbell.com/flicker.jpg
http://www.alasdaircampbell.com/flicker2.jpg

I assume we are talking about CRT Display !

A problem with the Degaussing Circuit ?? affecting the Electron
Beam,only. Not the Power Supply and the Sync , and Video circuits

After a few seconds the Degaussing circuits should shut down.
In this case , it does not ! and would apparently affect all inputs.

It looks like my CRT Monitor, a few seconds into Warm-up when the
Degaussing Circuit is still Active !

The Flicker is due to the fact that your scan rate isn't the same or
close to the
Power Line Frequency ???

Yukio YANO

 

[Alasdair Campbell]

I assume we are talking about CRT Display !

Yes, sorry for not making that clearer.

A problem with the Degaussing Circuit ?? affecting the Electron
Beam,only. Not the Power Supply and the Sync , and Video circuits

After a few seconds the Degaussing circuits should shut down. In this
case , it does not ! and would apparently affect all inputs.

It could be degaussing related, as when power is applied from cold, the
problem takes a few minutes to appear. After successive power cycles, the
problem is immediate. Perhaps that's a red herring though.

It looks like my CRT Monitor, a few seconds into Warm-up when the
Degaussing Circuit is still Active !

The Flicker is due to the fact that your scan rate isn't the same or
close to the
Power Line Frequency ???

Yukio YANO

Which board in a modern CRT controls the scan rate?

Alasdair