1. Home
  2. Electronics Repair
  3. Panasonic TV model CT-20G11U image distortion: solved, but new puzzle

Panasonic TV model CT-20G11U image distortion: solved, but new puzzle

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...

Reply to
chibitul
Loading thread data ...

"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.

Reply to
Asimov

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 . .

Reply to
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 . .

Reply to
electricitym

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.