A problem I notice on many TV's

[MRX37]

Sometimes, especally if there are bright areas in the picture, a TV's picture will distort a bit. The best example of this is straight bars that end up curving a bit when the picture gets brighter.

The 25" Samsung TV I found awhile back does this. It kinda annoys me as I've been using it as a computer monitor. When a window pops up, the sides of it are curved inwards, making it look slightly trapezoidal like.

I notice many TV's that do this, so I'm wondering if it's an actual problem, or just a characteristic of the design? I know TV's aren't designed as good as computer monitors are...

[zenith2134]

The bending of vertical lines occurs when the contrast and brightness are jacked up too high, and the HV supply lags making the picture 'bloom'.... Actually I have noticed this on many sets, old or new, and if the power supply's electrolytic filters are changed out it can make a world of difference.

[MRX37]

Well, I don't have the brightness set very high on it. The factory default is actually a bit higher then what I have it set at.

Are the power supply's electrolytic filters those large caps that need to be discharged before removing them?

[andy]

000

[MRX37]

Well, this TV is a few years old. It was made in 2001. If something's drifting out of spec, I wouldn't mind fixing it before it becomes a huge issue.

[MRX37]

Originally Posted by zenith2134

Actually I have noticed this on many sets, old or new, and if the power supply's electrolytic filters are changed out it can make a world of difference.

So are these the caps that are large and hold a high voltage even after the set is unplugged?

[RetroHacker]

Originally Posted by MRX37

So are these the caps that are large and hold a high voltage even after the set is unplugged?

They hold some voltage. Not a ton, like the picture tube. Discharge them before you remove them though, just to avoid an unpleasant zap.

And yes, this is pretty normal - replacing the filters should help, but you may not be able to get rid of it entirely.

-Ian

[MRX37]

Oh I know it wouldn't be perfect. I've never seen a "perfect" TV. but this tv is "good enough" and has very vivid color, and since replacing the filter caps wouldn't do any harm...

I might just do that.

[old_tv_nut]

Don't get your hopes too high about changing caps, but try it if you want to.

Also, a terminology problem - you've been saying "brightness", but it's the "contrast" you need to back off on to reduce the beam current and reduce this problem.

Edit: or "Picture" control if that's what it has

[zenith2134]

old_tv_nut... thats true... Interestingly enough, Sony's usually have better regulation IME, and they're the ones which call contrast 'picture' . Some older Zeniths used white level/black level, which is without a doubt the more accurate name for the controls...

If I wanted to stiffen up the supply, I would increase the capacitance on the related lytics 'slightly' so as to not burn up any diodes. Say 15-20% increase or so, couldn't really hurt...