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Does the RF modulator on a heavy sixer come apart?


MaximRecoil
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That is, without breaking anything? It looks like the metal housing snaps together, but in order to get it apart, I'd have to remove it from the PCB first. I don't want to remove it from the PCB just to find out I can't open it up without damaging something though.

 

Also, what components are in there? I'm guessing there is at least one or more electrolytic capacitors, and if so, I'd like to replace it/them.

 

My heavy sixer has great colors and sharpness, but it has more RF interference in the picture than my 7800 (which has dull colors), and more than my other five 2600s as well (3 light sixers, 2 4-switch woodgrains). Those all have good colors (not quite as good as the heavy sixer; the 2 4-switch ones had very poor colors until I did that official Atari Field Service Manual resistor modification to them), with the 4-switch ones having the least amount of RF interference patterns, and the 7800 having the least of all.

 

I've already replaced all of the electrolytic capacitors that I can see, as well as the "chicklet" capacitors on the switch panel. Now I'm wondering if there are capacitors in the RF modulator which might be out-of-spec and causing this.

 

Just to be clear, I'm not talking about white snowy static interference, which is indicative of a weak signal, bad connection, or very strong interference such as when someone turns on a vacuum cleaner. I'm talking about subtle, semi-random, constant shadowy motion within the colors of the graphics; some colors show it more than other colors, and it isn't there at all in black backgrounds. All RF video signals have this type of RF interference to one extent or another, but some consoles have much less of it than others. The NES front-loader's RF signal is the cleanest I've ever seen, for example, though it still has ever-so-slight interference.

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Be aware that sometimes RF modulators are aligned and tuned by bending the coils and repositioning parts. Been a while since I opened up a VCS modulator but I think you'll find ceramic disc caps in there, they don't go out of tolerance as quickly as electrolytics.

 

I'm also willing to bet the NES has a more complex and comprehensive modulator than the VCS.

 

Anyways, what parts do you plan to replace?

https://atariage.com/2600/archives/schematics/Schematic_2600_RFSections_High.html

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Found this pic.. says its from the 7800 but sure as hell looks the same as a vcs modulator.

http://blog.kevtris.org/blogfiles/fpga2600/7800mod2.JPG

 

Thanks. There are no electrolytic capacitors in there, and I'm not worried about ceramic disc capacitors. The NES RF modulator has a few/several electrolytic capacitors, some for the composite output (which is in the same housing as the RF modulator circuitry) and some for the RF modulator section.

 

I'm beginning to think there's no fixing the RF interference without redesigning the motherboard and/or RF modulator. I suspect it gets into the RF signal from within. Just to refresh my memory, I just tried Missile Command on all 7 of my Ataris:

 

RF interference from most to least:

 

- Heavy sixer

- Two light sixers

- One light sixer

- Two 4-switch woodgrains

- 7800

 

The 7800 has the least by far, while the rest of them are pretty close to each other. I wonder if it's because of the 7800's significantly less-saturated colors. If I switch the heavy sixer to B&W mode, most of the RF interference goes away, bringing it down to the level of the 7800. Like with the 7800, the only RF interference that's there on the heavy sixer in B&W mode is faint patterns with very little motion. Turn on the color and the RF interference comes "alive", i.e., full of motion. Also, that one light sixer with less RF interference than the other sixers, also has the worst colors of the four (the heavy sixer has the best colors). So it seems that the chroma signal is more affected by the interference than the luma signal is.

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Well. Yes. That makes sense.

 

They way I see it (and my attitude toward it) is always remember its 40 year old electronics - and parts will fall out of tolerance. These consoles were made for the TV sets of the time, too, and they likely depended upon some slack and less sensitivity to mask some noise and signal defects. Note I didn't say CRT, but TV set. And that means the tuner and color processing circuitry in vogue at the time was likely a factor in how the VCS made colors and all that.

 

Also these ancient 'tronics are probably more sensitive to environmental conditions like humidity than we think. And mixed signal ICs of the 70's can't be the most noise-free components either. All electronic parts are going to age at slightly different rates. The image quality of any given batch of 100 VCS units is going to vary and diverge more and more with time.

 

Lots of factors at work. And not all of them have been fully examined. Let alone understood. And it also bears mentioning that it will take more and more skill to repair and adjust these older consoles. Component level repair, electronics theory going beyond a battery and a lightbulb. Repair and troubleshooting knowledge gained through formal training. Knowledge going beyond swapping parts just because they're in the block that does what someone thinks it does. And then you need all the test equipment and knowledge to use it. And all this hubbub and fretting! It's maddening!

 

All in all I fear that most folks will give up and find their classic fix via another entirely different method.

 

Back in the fall of 1977 when I got my first VCS I clearly recall hooking it up and seeing gorgeously saturated and razor sharp images. And through the rose colored nostalgia goggles we all have (actually less brain cells to remember the subtle defects), a properly tuned and configured emulator comes pretty damed close to replicating the early images as I remember them. Key point being as remembered. The two technologies, side by side, produce images with different characteristics and are worlds apart on some aspects.

 

In thinking about the Flashbacks and other mini-consoles with built-in games, I wonder why they're going with emulation & simulation as opposed to simply copying the chips? The chips in the VCS are certainly simple. Yes?

 

I think it has to do with image clarity and working entirely in the digital domain and matching the output (of the mini-console) to modern display devices. Working entirely in digital domain has a huge number of advantages. Enough to outweigh the disadvantages. Understand that in a mini-console with HDMI, the only analog-style signal present is the AC coming into the power adapter. Scratch that if it's USB powered - you got your solid steady DC right there. The signal, Game Program, processing, game logic, controller input, video and audio out are 100% digital and stay that way all the way through firing (or twisting) of the pixels on the display panel. And even then they are activated in discrete steps, in a matrix fashion. Sound? Yup. That speaker cone is moving digitally too. Blow up a ship, and it will vibrate the exact same amount from one explosion to the next. It will do exactly what the software tells it to do. Same pattern, amplitude, duration, all that.

 

That affords unprecedented control of what the game looks and sounds like. All this totally unimaginable in the 1970's. My whole point being is that we're being exposed to more and more digital content that is highly repeatable and rather flawless within the scope of things. Movie theaters are awesome now with matured DLP. Smartphones exceed standard HD. Blu-ray and 4K are here, have been here. And I think classic gaming needs to move more this way, through emulation in software or in FPGA.

 

We shouldn't expect the same level of performance from classic consoles. We can mod them. And have done so. And have gotten closer to how we remember them as kids of the 80's. But in order to be satisfied again we must work entirely in the digital domain. Analog be gone!

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I'm beginning to think there's no fixing the RF interference without redesigning the motherboard and/or RF modulator. I suspect it gets into the RF signal from within.
Likely yes. Gotta come from someplace.
But consider, the units were interference-free when new I assume.. Right? So what would have changed in the intervening years? Certainly not the design of the motherboard.
Could the type of TV set and its tuner be different? Could parts be aging? And the right way to fix those 2 issues is to acquire a TV set that "likes" the VCS output. And/or replace aged components.

Conducting video mods is essentially making a revision to the mainboard. While not changing electrical traces directly or anything, you are indeed redoing the output. More than enough to warrant a new revision number or letter. And if it works, great!

 

 

RF interference from most to least:

 

- Heavy sixer

- Two light sixers

- One light sixer

- Two 4-switch woodgrains

- 7800

 

The 7800 has the least by far, while the rest of them are pretty close to each other. I wonder if it's because of the 7800's significantly less-saturated colors.

 

Interesting to note that the list progresses in the same order as the models/units were manufactured. Could it simply be that the later 7800 has parts that are more stable, and a more conservative and tolerant design?
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Movie theaters are awesome now with matured DLP.

 

I hate it. I love film projectors on the other hand.

 

By the way, the picture from my Ataris, and all other video sources, look a lot better to me today on my 32" manufactured-in-2006 (and still like new) CRT than they ever did when I was a kid. My current TV has beautiful, bright, perfectly adjusted color, contrast, and sharpness, and it was that way new out of the box. The TV isn't even anything special (a $250 RCA from Wal-mart), but the technology was at its peak of maturity in 2006, and they had gotten really good at making them.

 

But consider, the units were interference-free when new I assume.. Right? So what would have changed in the intervening years? Certainly not the design of the motherboard.

 

I doubt they had much, if any, less interference when new. They definitely wouldn't have been 100% interference-free, because I don't think that's even possible for an RF signal. Even the NES front-loader, which has the cleanest RF output I've ever seen, has some interference if you look closely enough. The Atari 2600 I bought new in 1985 ("Vader" model) never looked great back then, though it was good enough, because nothing looked great on home TVs back then. The only other video sources aside from consoles/computers were over-the-air TV broadcasts and VCRs, both of which were delivered via RF, and neither of which were impressive (for most people anyway; some enthusiasts had LaserDisc players and a TV with composite input, and those looked a lot better).

 

Even as a kid I wondered why the picture on arcade machines was so clean compared to what I saw on TV sets. I remember being about 7 years old and staring up at the screen of a Pole Position machine, and being amazed at how crystal clear and sharp it was. "How did that do that?" I asked people. "It looks like a regular TV tube, but that can't be a regular TV inside." I didn't know anything about different types of video signals backs then.

 

Interesting to note that the list progresses in the same order as the models/units were manufactured. Could it simply be that the later 7800 has parts that are more stable, and a more conservative and tolerant design?

 

Yes, but they also get progressively worse in color. My heavy sixer has brilliant colors, some of the most saturated/vibrant colors I've ever seen from any video source, while the colors of the 7800 are a joke. They are only a small step above black & white. I'd have to reduce the default color saturation setting on my TV by more than half before my heavy sixer's colors would look as dull as the 7800's colors.

 

If whatever is causing the RF interference is affecting the chroma signal more than it does the luma signal (which are separate on a TIA, which is why you can get S-video from them natively), then it stands to reason that the more saturated the color is, the more RF interference you'll see.

Edited by MaximRecoil
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But consider, the units were interference-free when new I assume.. Right? So what would have changed in the intervening years? Certainly not the design of the motherboard.

 

I've thought about this a bit and actually quite a bit has changed that could cause these issues today. Think about how much the radio spectrum has changed and its use in our day to day lives? We now use RF in many other ways outside of just broadcast TV. We now have more radio interference throughout our homes than what could ever have been thought of BITD. Hell I even noticed additional interference now happening on my consoles I hadn't modded that used to exhibit excellent RF picture such as my Intellivision and Colecovision. Over the past year those have had to be modded with composite AV so they look good and are essentially playable again.

 

BTW...not sure about the rest of you but I noticed a lot of this interference in my 2600s and the like started around the same time they converted all the electric meters in my neighborhood to digital. Those new digital meters attach wirelessly back home for monitoring so that the traditional meter reader isn't required anymore. And the new meter happens to be installed just opposite the wall of my game room. Coincidence? Perhaps....

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Here's a good example (heavy sixer):

 

BF1Ee0t.jpg

 

The RF interference is in the form of faint, shadowy diagonal lines (and there is some motion to them, sort of a scrolling motion, but not in a uniform speed and direction). That mostly applies to green. The interference takes on other patterns in other colors, sometimes shifting back and forth between one pattern to another, and sometimes just being patternless (random) motion.

 

By comparison, this is from my Atari 7800:

 

kOI8wzf.jpg

 

Crappy colors, but not much RF interference and not much, if any, motion to what little interference there is.

 

Click on the pictures to view them fullsize. The automatic resizing that this forum software imposes on embedded pictures wider than 600 pixels is adding a moire effect which isn't really there.

Edited by MaximRecoil
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