Is This Normal

[TinCanAlley]

Since I have the Avante open to fix the remote control board and volume pot, I figure I might as well address a couple other issues I've been noticing.

Since the set is 51 years old, this issue might just be a limitation of the technology, but I need to find out. Ignore the jailbars in the attached image. I've pretty much given up on fixing that. You'd think after 12 years I would have found someone that either knows what causes it or knows someone that does. I'm still looking. Anyway, the issue has to do with screen brightness during transitions. In the attached image, the screen was black with a logo on it. Then the video fades as most TV shows do at the point of either inserting commercials or transitioning scenes. On a Hitachi from 81 (the only other CRT TV I have), the screen stays black, but on the Avante it turns greyish green until an image comes back. Is that a fixable issue, or just the way it is?

[old_tv_nut]

Gray is normal on a set with less than 100% DC restoration (don't know if this applies to this particular model).

Green is not normal. Maybe just needs a slight G2 adjustment for good gray scale tracking?

Those jail bars are pretty ugly. Sorry I don't know the particular fix; guess I would play with grounds and lead dress.

[TinCanAlley]

Originally Posted by old_tv_nut

Gray is normal on a set with less than 100% DC restoration (don't know if this applies to this particular model).

Green is not normal. Maybe just needs a slight G2 adjustment for good gray scale tracking?

Those jail bars are pretty ugly. Sorry I don't know the particular fix; guess I would play with grounds and lead dress.

I'm assuming a CCII has the DC Restore. Any idea what board it would be on (Chroma, Video IF, Video Processor...)?

I'm confident the G2 is set properly. When fed a good signal, the set produces a very good image, brightness, contrast and color. While the whites aren't has pure as I'd like, no combination of the three color taps will give a pure white. The best I can do is a white that's a bit bluer (cooler) than it should be.

If you look back through threads from around 2013, you'll find many pages of back and forth trying to solve the jailbars. I was told it was ringing, but when I scope the brightness circuit and see the wave of ringing, many would say it doesn't look like it or that wouldn't cause your issue. It was like that for just about all possible ringing sources, so I just gave up.

Thanks for you input!

[vol.2]

Originally Posted by TinCanAlley

I'm assuming a CCII has the DC Restore. Any idea what board it would be on (Chroma, Video IF, Video Processor...)?

I'm confident the G2 is set properly. When fed a good signal, the set produces a very good image, brightness, contrast and color. While the whites aren't has pure as I'd like, no combination of the three color taps will give a pure white. The best I can do is a white that's a bit bluer (cooler) than it should be.

If you look back through threads from around 2013, you'll find many pages of back and forth trying to solve the jailbars. I was told it was ringing, but when I scope the brightness circuit and see the wave of ringing, many would say it doesn't look like it or that wouldn't cause your issue. It was like that for just about all possible ringing sources, so I just gave up.

Thanks for you input!

The color tracking could just be the way you set the balance up. To dial it in really good, I think it takes a colorimeter.

Typically, you can get very good tracking by going back and forth between 20 IRE and 120 IRE with the background and drive adjustments, starting from wherever the manual tells you to. You can use something like HFCR and a cheap meter from the 90s to dial it in, and then do a greyscale test.

In most cases, I find that the potentiometers they provide from the factory do not have an adequate number of turns to really dial in the color, and they will often skip over the sweet spots very easily. Especially the color transistions on the backgrounds tend to be extremely fussy because the color tracking at low light is a lot worse. However, a small mistake in the bias controls can translate into a larger error at higher IRE levels, forcing you to compensate and throwing off your tracking.

If you care about it, you should be able to get it better than "looks too blue" if you want.

As for the jailbars, I have had a lot of annoying jailbar issues I could never solve, but none of them looked that severe. I would maybe look at the value of the caps on the snubber and damper diode on the horizontal yoke, assuming that they exist, or something like that exists on your set. Those are there specifically to suppress ringing. Just a thought, and I am not really familiar with you set. I generally work on stuff later than 1975.

[TinCanAlley]

Originally Posted by vol.2

The color tracking could just be the way you set the balance up. To dial it in really good, I think it takes a colorimeter.

Typically, you can get very good tracking by going back and forth between 20 IRE and 120 IRE with the background and drive adjustments, starting from wherever the manual tells you to. You can use something like HFCR and a cheap meter from the 90s to dial it in, and then do a greyscale test.

In most cases, I find that the potentiometers they provide from the factory do not have an adequate number of turns to really dial in the color, and they will often skip over the sweet spots very easily. Especially the color transistions on the backgrounds tend to be extremely fussy because the color tracking at low light is a lot worse. However, a small mistake in the bias controls can translate into a larger error at higher IRE levels, forcing you to compensate and throwing off your tracking.

If you care about it, you should be able to get it better than "looks too blue" if you want.

As for the jailbars, I have had a lot of annoying jailbar issues I could never solve, but none of them looked that severe. I would maybe look at the value of the caps on the snubber and damper diode on the horizontal yoke, assuming that they exist, or something like that exists on your set. Those are there specifically to suppress ringing. Just a thought, and I am not really familiar with you set. I generally work on stuff later than 1975.

I started to research replacing the taps with pots, but I'm pretty new to this sort of thing and couldn't figure out where to cut out the circuits for the taps and insert the pot. I figure a pot that covered the range of the taps and that would allow me to finely adjust and not just pick between 3 set values.

I'm assuming the caps you're referring to aren't electrolytic, as I replaced every electrolytic when I got it and I recreated the inside of the canister so to keep it looking original. I have the SM and will try to find what you mentioned.

[vol.2]

Originally Posted by TinCanAlley

I figure a pot that covered the range of the taps and that would allow me to finely adjust and not just pick between 3 set values.

It should do so. I have never seen a set that had steps for the color controls as opposed to a continuously adjustable pot, if that's what you're saying this one has. I've only ever worked on Japanese sets, and never seen such a thing.

However, if the color controls are indeed steps (tap locations) instead of pots, I would also double check the schematic to make sure that adding a pot in a "normal" configuration wouldn't create an electrical issue. I can't imagine how it would do so, but then I've also never seen what you're describing.

I'm assuming the caps you're referring to aren't electrolytic

No, they absolutely wouldn't be. They would be high voltage ceramic caps of a low value probably. Something like 300-600pF at something like 1.5-3kV maybe. Again, I'm clearly not super familiar with the American sets from those days, but I would guess they must have some ring suppression on the H yoke; there's usually a damper diode on the primary of the flyback windings that feeds the yoke in my experiences. There can also be another one somewhere on the other side (snubber) that would look similar if it exists. If so, they may have caps in parallel. Those are supposed to suppress the ringing by smoothing out the electronic whacking of the deflection.

[TinCanAlley]

Originally Posted by vol.2

It should do so. I have never seen a set that had steps for the color controls as opposed to a continuously adjustable pot, if that's what you're saying this one has. I've only ever worked on Japanese sets, and never seen such a thing.

However, if the color controls are indeed steps (tap locations) instead of pots, I would also double check the schematic to make sure that adding a pot in a "normal" configuration wouldn't create an electrical issue. I can't imagine how it would do so, but then I've also never seen what you're describing.



No, they absolutely wouldn't be. They would be high voltage ceramic caps of a low value probably. Something like 300-600pF at something like 1.5-3kV maybe. Again, I'm clearly not super familiar with the American sets from those days, but I would guess they must have some ring suppression on the H yoke; there's usually a damper diode on the primary of the flyback windings that feeds the yoke in my experiences. There can also be another one somewhere on the other side (snubber) that would look similar if it exists. If so, they may have caps in parallel. Those are supposed to suppress the ringing by smoothing out the electronic whacking of the deflection.

I am determined to get this.....

I'm attaching 2 pics. In the one from the underside of the horizontal ouput, I'm assuming there is a high voltage cap and diode. The diode must be the damper diode and the cap is noted as "safety cap". In the second pic, it's the flyback connections from the HOT and there are two more safety caps. All the caps were replaced 12 years ago, except the ceramic on the underside of the HOT. The diode is original to the set.

Am I looking the the right place?

[TinCanAlley]

I should add that the set does have separate G2 controls for red, green and blue. You adjust those in setup mode to equal intensity and then go back to normal mode and with a black and white image, you adjust the taps to remove any color in the white areas of the image.

I should add that I've tried the setup switch and it does not produce a bright enough line for any of them, so I did it with a pattern generator and adjusted to get the best white lines. It was then I used a black and white image to adjust the taps. Maybe not the best way to do it, but I've been unable to figure out why the setup isn't working. I cleaned the switch and and checked the circuit, but I'm just not finding it. The CRT is good and the image is bright, just can't use the internal setup for the setup line(s).

[vol.2]

Originally Posted by TinCanAlley

I am determined to get this.....

I'm attaching 2 pics. In the one from the underside of the horizontal ouput, I'm assuming there is a high voltage cap and diode. The diode must be the damper diode and the cap is noted as "safety cap". In the second pic, it's the flyback connections from the HOT and there are two more safety caps. All the caps were replaced 12 years ago, except the ceramic on the underside of the HOT. The diode is original to the set.

Am I looking the the right place?

Assuming that it is the damper diode, I believe that it could cause the ringing if it's gone leaky. The cap could also do so if it's massively altered in value, or gone open or short. Those components get beat to hell by the deflection circuitry, so it's a fair thing to at least check them out of circuit. Both have to handle very high pulses, so sometimes I just replace them to be safe. One can easily and cheaply acquire new diodes that can handle much more abuse than they could make in the 70s. If you're placing an online order for parts, it would not hurt to buy those parts and replace them. It would be a few bucks tops for the parts, probably less than half of the shipping. If this is the only thing you are buying, then maybe just test the components first to see if anything looks fishy. The shipping from digikey or mouser for that handful of parts would be like $5 for slow USPS, so it wouldn't be worth it for me to buy them alone. Probably end up costing you like $10 for $2.50 worth of parts. If they do no help, that's wasted $10.

To determine what they are, I would have to get eyes on their position in the schematic as I'm not used to seeing those older sets. I watch Shango on youtube fix them, but I've never poured over a schematic for one.

Zeno or others on this forum could easily tell you what the suppression components in your set are without even looking at the schematics I believe. I wish I could be so helpful

[TinCanAlley]

Originally Posted by vol.2

Assuming that it is the damper diode, I believe that it could cause the ringing if it's gone leaky. The cap could also do so if it's massively altered in value, or gone open or short. Those components get beat to hell by the deflection circuitry, so it's a fair thing to at least check them out of circuit. Both have to handle very high pulses, so sometimes I just replace them to be safe. One can easily and cheaply acquire new diodes that can handle much more abuse than they could make in the 70s. If you're placing an online order for parts, it would not hurt to buy those parts and replace them. It would be a few bucks tops for the parts, probably less than half of the shipping. If this is the only thing you are buying, then maybe just test the components first to see if anything looks fishy. The shipping from digikey or mouser for that handful of parts would be like $5 for slow USPS, so it wouldn't be worth it for me to buy them alone. Probably end up costing you like $10 for $2.50 worth of parts. If they do no help, that's wasted $10.

To determine what they are, I would have to get eyes on their position in the schematic as I'm not used to seeing those older sets. I watch Shango on youtube fix them, but I've never poured over a schematic for one.

Zeno or others on this forum could easily tell you what the suppression components in your set are without even looking at the schematics I believe. I wish I could be so helpful

This works out perfectly. I needed to purchase a couple caps to try and fix the remote control board in the set, but spending 10 bucks for shipping on .60 worth of parts was not something I was looking forward to. Now I can purchase all the diode and cap replacements for the horizontal output section. That adds 8 more parts, so the shipping won't be so painful.

Off to Mouser site I go.

Thanks for all your help. I'll keep you informed.

[vol.2]

Originally Posted by TinCanAlley

Off to Mouser site I go.

Thanks for all your help. I'll keep you informed.

Ok. As I said, I'm not completely certain which diode you're looking at there. A schematic would be helpful, and then I'm not completely familiar with this old US made stuff and their topology.