JVC D Series Horizontal Smearing on the Composite Input

[BenM86]

Originally Posted by vol.2

Smearing to the right of bright objects is an incredibly common and ubiquitous symptom that can point to a wide range of faults.

Worst case the tube is shot and the smearing is caused by excessive voltages driving the video output IC too hard.

Essentially, the output IC will have a maximum voltage range it can operate in, for example some voltage that represents the most dark thing on the screen (positive voltage) and something else that represents the brightest thing on the screen (ideally close to zero in most cases). If the tube is too worn out, you will have to increase that range because the cathodes will require you push a more negative-going voltage to achieve a bright enough picture to see. When that happens, you can see smearing to the right as the video IC goes into "clipping."

The effect is very similar to audio clipping, but it often manifests in the video in this stretching out of the video to the right of the brightest objects because the brightest objects represent the most negative-going voltages on the raster.

Otherwise, it's capacitors somewhere. If I had to guess in the power supply or the deflection area. I don't know JVC set too well, but if it was my set and I was serious about it, I would just go through and test them all. It would probably take a couple evenings.

You can also check voltages on the schematic and see if anything is off. That would lead you to most faults of the kind you are looking at.

If it was an issue with the output or with the tube wouldn't it be the same across all the inputs?

Originally Posted by Alex KL-1

I can add some ramblings...
Some processing IC will have less effective bandwidth intentionally for composite inputs, for not interfering with chroma and vice-versa. A simple filtering near the HF range (end range) will smear the signal. Since the mentioned effect not occurs with S-Video for example, this is potentially the culprit.
Unless the opposite occurs; eg. a composite input with more sharpness enhancement, just for making up the composite lesser performance. So, it calls for more HF signal amplitude and can make the effects that vol.2 mentioned in great detail. This is harder when the set uses a simple transistor video output; generally these have too high collector output resistor value (15k being common for a lot of models; better sets have it less than 8k2 and even 4k7) and smears details due to limited slew rate it can resolve.
LATE EDIT: or the sources, with the know difficulties to join the Y to the C signal and smears due to that (some sources are better than others for it).

Interesting. So possibly just an issue with how the set was designed?

Originally Posted by zeno

My post from a few days ago on an MGA. only a few bucks to try.


Its probably the filter cap on the 200 V line. Its a top ten problem on
ALL sets. Symptoms are any combination of, or one of the following.

Pix goes from dark to light across the screen.
Pix just "not right",
Poor color, can look like bad CRT
Bright white raster with retrace lines.
Jail bars on left fading as you go right.
Streaking of brite content.
Cant turn brite down.
AND others that dont come to mind !

Zeno

Bottom line is change it on any SS set you are fixin !

Certainly seems like an easy thing to try. Could it affect just the composite input?