All white raster on Sony Wega TV

[Sparky]

This TV was working before we recently moved it -- without dropping the
175 lb beastie! Now with no inputs the raster is all white instead of
all black as it used to be. The brightness and picture controls (as
well as all of the other menu items) appear to operate and display normally
but the background raster remains a saturated white instead of black as it
used to. Unlike the main picture, the PIP picture has reasonable contrast but
it has no color, only black and white. You can see a just a tiny bit of
detail in the main picture. Since the PIP picture displays video and I have a
raster, I'm looking for problems in the luminance path for the main picture,
not the CRT grids or anything else CRT related. Looking at the schematic
makes me suspect that the PIP control is shot but all else is likely okay. Any
opinions on what may be wrong with the TV and where I might be able to source
a replacement circuit board?

Thanx!

Russ

 

[[email protected]]

This TV was working before we recently moved it -- without dropping the
175 lb beastie! Now with no inputs the raster is all white instead of
all black as it used to be. The brightness and picture controls (as
well as all of the other menu items) appear to operate and display normally
but the background raster remains a saturated white instead of black as it
used to. Unlike the main picture, the PIP picture has reasonable contrast but
it has no color, only black and white. You can see a just a tiny bit of
detail in the main picture. Since the PIP picture displays video and I have a
raster, I'm looking for problems in the luminance path for the main picture,
not the CRT grids or anything else CRT related. Looking at the schematic
makes me suspect that the PIP control is shot but all else is likely okay. Any
opinions on what may be wrong with the TV and where I might be able to source
a replacement circuit board?

Thanx!

Russ

You are not going to source a replacement circuit board. The tv needs
troubleshot and repaired to the component level.

 

[Michael Kennedy]

This TV was working before we recently moved it -- without dropping the
175 lb beastie! Now with no inputs the raster is all white instead of
all black as it used to be. The brightness and picture controls (as
well as all of the other menu items) appear to operate and display
normally
but the background raster remains a saturated white instead of black as it
used to. Unlike the main picture, the PIP picture has reasonable contrast
but
it has no color, only black and white. You can see a just a tiny bit of
detail in the main picture. Since the PIP picture displays video and I
have a
raster, I'm looking for problems in the luminance path for the main
picture,
not the CRT grids or anything else CRT related. Looking at the schematic
makes me suspect that the PIP control is shot but all else is likely okay.
Any
opinions on what may be wrong with the TV and where I might be able to
source
a replacement circuit board?

Thanx!

Since you say it was dropped, I'd look for cracks in the cirucit board and
also look for cracked solder joints.

- Mike

 

[Russ Panneton]

Since you say it was dropped, I'd look for cracks in the cirucit board and
also look for cracked solder joints.

- Mike

The mystery is that the TV malfunctions now but was NOT dropped during
the move. Pulling the back of and tapping everything inside didn't
expose any connections that are sensitive to mechanical vibration. More
troubleshooting to follow as I get the time...