JVC D Series Horizontal Smearing on the Composite Input

[vol.2]

You should also read this https://docs.google.com/document/d/1...it?usp=sharing

if you haven't before.

[BenM86]

Originally Posted by Alex KL-1

The "all-in-one" TV IC core can perhaps have different internal settings for each input, or simply the composite ones uses the comb filtering and that perhaps are not optimized (unlikely, but...)...
A lot of "perhaps" due to all these programmable IC's and it's features hidden for the users and even technicians; perhaps one bad choice for given model etc...

Difficult to pinpoit any direct culprit.

Originally Posted by vol.2

You should also read this https://docs.google.com/document/d/1...it?usp=sharing

if you haven't before.

Thanks! My particular model is a AV-32D302 with a Hitachi tube. And it uses the TB1253AN jungle chip and supposedly has a 3 line digital comb filter. I assume the comb filter is housed inside the jungle IC? Wonder if the IC has simply wore out.

[vol.2]

Originally Posted by BenM86

Wonder if the IC has simply wore out.

I seriously doubt it. It would be far more likely that some components somewhere are worn out or faulty.

Possibly it could have something to do with the settings, but I don't see how that could be true unless it was set wrong from the factory or someone has been in the settings and put something wrong. Normally it's setup correctly when it leaves the factory and the end-user doesn't have to mess with it.

It can be tempting to just try replacing a big IC because it seems like an easy thing to try, but it's very rarely the actual cause of failure in things like this.

When I have a big, difficult project like this, comparing voltages from the schematics is the number 1 way I make progress.

Doing this stuff can be really hard, and even after many years there are still some repairs I haven't figured out yet. It just be like that.

[BenM86]

Originally Posted by vol.2

I seriously doubt it. It would be far more likely that some components somewhere are worn out or faulty.

Possibly it could have something to do with the settings, but I don't see how that could be true unless it was set wrong from the factory or someone has been in the settings and put something wrong. Normally it's setup correctly when it leaves the factory and the end-user doesn't have to mess with it.

It can be tempting to just try replacing a big IC because it seems like an easy thing to try, but it's very rarely the actual cause of failure in things like this.

When I have a big, difficult project like this, comparing voltages from the schematics is the number 1 way I make progress.

Doing this stuff can be really hard, and even after many years there are still some repairs I haven't figured out yet. It just be like that.

I hear ya. It may end up being a juice not worth the squeeze situation. Overall the TV works almost perfectly. Probably easier to just find a S-VHS player with svideo out. The laserdisc is a little harder, good Elite units with good svideo out a super expensive. I may end up doing a recap one of these days just because and who knows that may help.

As far as the settings go, it's possible it's been messed with. D series TV's tend to trade hands often, so im sure the service menu has been accessed. The red push was already disabled when I got it, so someone has been in there at least once. I should at least sit down and make sure everything is set to factory based on the service manual just in case.

[vol.2]

Originally Posted by BenM86

As far as the settings go, it's possible it's been messed with. D series TV's tend to trade hands often, so im sure the service menu has been accessed. The red push was already disabled when I got it, so someone has been in there at least once. I should at least sit down and make sure everything is set to factory based on the service manual just in case.

I did have that thought. If you can do it safely, it's a good idea to make sure everything is correct. I wouldn't change any settings that aren't explicitly called out and explained in the service menu though; in my experience, many service menus contain options that are not documented for various reasons, and they shouldn't be messed with. Sometimes it has to do with some very basic operations that would never need to be changed, and sometimes they adjust things that weren't implemented in the circuit design (optional inputs and features).

There are absolutely settings in some service menus that will remove the picture, including the service menu text itself. If that happens, you're kind of screwed.

Again, I don't know JVC stuff too well, but I've run into it in other sets.

Recapping could help, but I'd recommend getting a good LCR meter (or an ESR meter if you want to save some money) and actually checking the caps you pull out rather than doing a shotgun. Sometimes shotgunning a set will end you up in worse shape than you started. This usually happens as a result of making mistakes (pulling up pads and traces, putting in caps backwards), but it can also happen because of less obvious mistakes such as using the wrong type of cap.

And that's why checking voltages is the way to go, because it points you to an issue in the operation of the circuit at a certain point. Once you discover a wrong voltage, you can scour the parts that would effect it and that should lead you to a problem. Sometimes there are multiple independent problems, or many problems caused by a cascade failure.

Whatever you're looking for seems like it's pretty specific though, because it's only on one input. Either the settings are wrong, or something touching only that input signal path is wrong. I like those chances.

But yeah, make sure the settings are correct first.

[BenM86]

Originally Posted by vol.2

I did have that thought. If you can do it safely, it's a good idea to make sure everything is correct. I wouldn't change any settings that aren't explicitly called out and explained in the service menu though; in my experience, many service menus contain options that are not documented for various reasons, and they shouldn't be messed with. Sometimes it has to do with some very basic operations that would never need to be changed, and sometimes they adjust things that weren't implemented in the circuit design (optional inputs and features).

There are absolutely settings in some service menus that will remove the picture, including the service menu text itself. If that happens, you're kind of screwed.

Again, I don't know JVC stuff too well, but I've run into it in other sets.

Recapping could help, but I'd recommend getting a good LCR meter (or an ESR meter if you want to save some money) and actually checking the caps you pull out rather than doing a shotgun. Sometimes shotgunning a set will end you up in worse shape than you started. This usually happens as a result of making mistakes (pulling up pads and traces, putting in caps backwards), but it can also happen because of less obvious mistakes such as using the wrong type of cap.

And that's why checking voltages is the way to go, because it points you to an issue in the operation of the circuit at a certain point. Once you discover a wrong voltage, you can scour the parts that would effect it and that should lead you to a problem. Sometimes there are multiple independent problems, or many problems caused by a cascade failure.

Whatever you're looking for seems like it's pretty specific though, because it's only on one input. Either the settings are wrong, or something touching only that input signal path is wrong. I like those chances.

But yeah, make sure the settings are correct first.

Well, the plot thickens. I have no idea why I didn't try this before. I went ahead and plugged the DVD player into the composite input which I had never done before, aaaand, its fine. So I guess there's nothing hardware wrong on the TV. I still dont understand why the issue is happening though.

Id be willing to believe the VCR and laserdisc are both just worn out, but then why don't they have the same artifacting on my other TV's? ill attach two comparison shots one with the episode 1 vhs and one with the episode 2 dvd. The vhs should of course be worse, but not THAT much worse. Same input, same settings on the TV and camera. And again, the VCR does not look this bad plugged into any of my hdtvs, just this one. Somehow im even more confused than I was before lol.

[vol.2]

Originally Posted by BenM86

Id be willing to believe the VCR and laserdisc are both just worn out, but then why don't they have the same artifacting on my other TV's?

It could be that the "HDTVs" simply have a greater tolerance for noise or excessive voltage in the signal.

Your VCR and Laserdisc players could be worn out, and the JVC could also have some weak components, and it's only when two weakened devices are combined that you see the greatest issues in the raster.

The DVD player is a newer device with a much cleaner signal.

Either way, you shouldn't be seeing all that smearing and ghosting, and there's either something wrong with both the Laserdisc player and the VCR, there's something wrong with the TV, or both.