Hi,

following your great advice my friends, I replaced the capacitor in the
vertical circuit (c455, near the IC LA78xx) and now the image distorion
at the top is gone. I ran the set for over an hour, it *seems* fine.

However, here is the puzzle: the TV set was off (unplugged and open up)
for two days while I was looking for thge right component. I think I
identified the capacitor very precisely, the defect was stronger when I
sprayed cold frozen gas (canned air) on c455, and it was almost gone
when I heated the entire area with a hair drier.

But, after replacing the capacitor, first time I turned the TV ON, I
saw the image distortion for a few seconds, and since then it is
gone!!! I wonder myself if I fixed it indeed, or there is something
else (cold joint, another component, etc.) and it will come back in a
few days.

Could the vertical IC be so smart, that it tries to compensate for the
distortion, and when I turned the TV ON with the new capacitor, it
tried to compensate for a defect that wasn't there, and after a few
seconds it realized there is no need to compensate and the image is
fine since then???


Sorry for the long and detailde description, but I don't know what to
think now...

"chibitul" bravely wrote to "All" (14 Jul 05 17:13:41)
--- on the heady topic of "Panasonic TV model CT-20G11U image distortion:
solved, but new puzzle"

ch From: "chibitul"
ch Xref: aeinews sci.electronics.repair:53216

ch Hi,

ch following your great advice my friends, I replaced the capacitor in
ch the vertical circuit (c455, near the IC LA78xx) and now the image
ch distorion at the top is gone. I ran the set for over an hour, it
ch *seems* fine.
ch However, here is the puzzle: the TV set was off (unplugged and open
ch up) for two days while I was looking for thge right component. I think
ch I identified the capacitor very precisely, the defect was stronger when
ch I sprayed cold frozen gas (canned air) on c455, and it was almost gone
ch when I heated the entire area with a hair drier.

ch But, after replacing the capacitor, first time I turned the TV ON, I
ch saw the image distortion for a few seconds, and since then it is
ch gone!!! I wonder myself if I fixed it indeed, or there is something
ch else (cold joint, another component, etc.) and it will come back in a
ch few days.

ch Could the vertical IC be so smart, that it tries to compensate for the
ch distortion, and when I turned the TV ON with the new capacitor, it
ch tried to compensate for a defect that wasn't there, and after a few
ch seconds it realized there is no need to compensate and the image is
ch fine since then???


ch Sorry for the long and detailde description, but I don't know what to
ch think now...


Could be the new electro was slightly unformed and what you saw was it
settling down to the normal alive state. An electrolytic capacitor is
like a Stradivarius, if it isn't used it dies.

A*s*i*m*o*v

.... A stereo system is the altar to the god of music.

chibitul:
Many times... when you find ONE bad capacitor, there could be more.
If the problem continues.... upon cold turn on after the set has been
off overnite then the problem is still lurking.
If you do not have an ESR meter to test them, then you will have to
substitute/replace other suspected bad capacitors to find them. There
are only a half dozen or so in the vertical output circuitry so this is
not a big task. Heck, to save time, just replace all of them in that
area of the circuitry.
electricitym
..
..

chibitul:
Many times... when you find ONE bad capacitor, there could be more.
If the problem continues.... upon cold turn on after the set has been
off overnite then the problem is still lurking.
If you do not have an ESR meter to test them, then you will have to
substitute/replace other suspected bad capacitors to find them. There
are only a half dozen or so in the vertical output circuitry so this is
not a big task. Heck, to save time, just replace all of them in that
area of the circuitry.
electricitym
..
..