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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Snowy Picture on LG Plasma TV



 
 
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  #1  
Old January 16th 09, 05:11 AM posted to sci.electronics.repair
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Posts: 3
Default Snowy Picture on LG Plasma TV

My LG plasma (42px50) has a "snowy" background. By "snowy" I mean
that a constantly changing random pattern of isolated pixels flash - a
little like the old days when you would see static on the screen if
your antenna wasn't positioned properly. This isn't as pronounced as
that, but the idea is similar. This applies across all inputs (cable
box, DVD, etc.) I have component cables from the DVD and HDMI from
the cable box. I have tried replacing the cables and the cable box,
but he problem is consistent. Even during that momentary black screen
that occurs when switching between inputs, the snow remains. It seems
clear to me that this problem is not coming from the components or
from the cables, but must be with the tv itself. Even when I select
an input that is not connected to any device, the snowy picture
continues.

Does anybody know why this might be happening or what I can do to
correct it? Thanks.
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  #2  
Old January 16th 09, 05:25 AM posted to sci.electronics.repair
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Posts: 387
Default Snowy Picture on LG Plasma TV

Randy wrote:
My LG plasma (42px50) has a "snowy" background. By "snowy" I mean
that a constantly changing random pattern of isolated pixels flash - a
little like the old days when you would see static on the screen if
your antenna wasn't positioned properly. This isn't as pronounced as
that, but the idea is similar. This applies across all inputs (cable
box, DVD, etc.) I have component cables from the DVD and HDMI from
the cable box. I have tried replacing the cables and the cable box,
but he problem is consistent. Even during that momentary black screen
that occurs when switching between inputs, the snow remains. It seems
clear to me that this problem is not coming from the components or
from the cables, but must be with the tv itself. Even when I select
an input that is not connected to any device, the snowy picture
continues.

Does anybody know why this might be happening or what I can do to
correct it? Thanks.



A noisy or oscillating powersupply?
  #3  
Old January 16th 09, 04:40 PM posted to sci.electronics.repair
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Posts: 3
Default Snowy Picture on LG Plasma TV

On Jan 15, 9:25*pm, Sjouke Burry
wrote:
Randy wrote:
My LG plasma (42px50) has a "snowy" background. *By "snowy" I mean
that a constantly changing random pattern of isolated pixels flash - a
little like the old days when you would see static on the screen if
your antenna wasn't positioned properly. *This isn't as pronounced as
that, but the idea is similar. *This applies across all inputs (cable
box, DVD, etc.) *I have component cables from the DVD and HDMI from
the cable box. *I have tried replacing the cables and the cable box,
but he problem is consistent. *Even during that momentary black screen
that occurs when switching between inputs, the snow remains. *It seems
clear to me that this problem is not coming from the components or
from the cables, but must be with the tv itself. *Even when I select
an input that is not connected to any device, the snowy picture
continues.


Does anybody know why this might be happening or what I can do to
correct it? *Thanks.


A noisy or oscillating powersupply?


How would I test for this? The TV is plugged into a power strip which
is plugged into the wall.
  #4  
Old January 17th 09, 04:37 AM posted to sci.electronics.repair
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Posts: 387
Default Snowy Picture on LG Plasma TV

Randy wrote:
On Jan 15, 9:25 pm, Sjouke Burry
wrote:
Randy wrote:
My LG plasma (42px50) has a "snowy" background. By "snowy" I mean

cut
A noisy or oscillating powersupply?


How would I test for this? The TV is plugged into a power strip which
is plugged into the wall.

Inside the tv.
Your incoming power is converted to 1 or more
internal supply voltages.
Check with an oscilloscope.
  #5  
Old January 17th 09, 07:22 AM posted to sci.electronics.repair
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Posts: 201
Default Snowy Picture on LG Plasma TV


This could be internal power supply noise. If you are experienced at
TV service you can use a scope and go through all the power supply
distributions to see if any of them are noisy.

Another cause could be a defect somewhere along the digital signal
path. There could be some system clocking errors, or some noise
generation taking place.


Jerry G.



On Jan 15, 11:11*pm, Randy wrote:
My LG plasma (42px50) has a "snowy" background. *By "snowy" I mean
that a constantly changing random pattern of isolated pixels flash - a
little like the old days when you would see static on the screen if
your antenna wasn't positioned properly. *This isn't as pronounced as
that, but the idea is similar. *This applies across all inputs (cable
box, DVD, etc.) *I have component cables from the DVD and HDMI from
the cable box. *I have tried replacing the cables and the cable box,
but he problem is consistent. *Even during that momentary black screen
that occurs when switching between inputs, the snow remains. *It seems
clear to me that this problem is not coming from the components or
from the cables, but must be with the tv itself. *Even when I select
an input that is not connected to any device, the snowy picture
continues.

Does anybody know why this might be happening or what I can do to
correct it? *Thanks.


  #6  
Old January 20th 09, 06:54 PM posted to sci.electronics.repair
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Posts: 17
Default Snowy Picture on LG Plasma TV

Randy wrote:
My LG plasma (42px50) has a "snowy" background. By "snowy" I mean
that a constantly changing random pattern of isolated pixels flash - a
little like the old days when you would see static on the screen if
your antenna wasn't positioned properly. This isn't as pronounced as
that, but the idea is similar. This applies across all inputs (cable
box, DVD, etc.) I have component cables from the DVD and HDMI from
the cable box. I have tried replacing the cables and the cable box,
but he problem is consistent. Even during that momentary black screen
that occurs when switching between inputs, the snow remains. It seems
clear to me that this problem is not coming from the components or
from the cables, but must be with the tv itself. Even when I select
an input that is not connected to any device, the snowy picture
continues.

Does anybody know why this might be happening or what I can do to
correct it? Thanks.


Does it do this on the menus also?,
if you go to the menu and select white wash or invert does
it seem to disappear ?, could your 'snow' be 'sparkles' ? if
so sounds like its the same fault mine had and it turns out
to be lots of 33uf caps on the power inverter board.
The board with four little transformers on, three in a row
at the top and one in the middle.

Test with an ESR meter and change, but I now need a manual
to set a couple of voltages to make it go away completely.

I'm told the board in these LG sets are the same on used in
Philips Plasmas?,
 




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