set 05 2017

Transcoding-Atari 2600 Rev. 17 for NTSC (Polivoks with American Board) – Part 1

Recently I spoke here in Skooter Blog on a Atari 2600 the Polivoks with American Board Rev. 17, I acquired, with the intention of installing a against 2600Tim RGB Worhington.

But before that removed the transcoding the Polivoks had made him, in other words, I modified it to work with the NTSC signal just like the original islands of the USA, instead of PAL-M signal that he worked on the factory made the Polivoks transcoding.

Remove the transcoding is needed to be able to install the 2600RGB? I am not sure. Might not be really necessary, for two reasons:

  1. PAL-M and NTSC are only different when it comes to RF signal, Composite video, S-Video and others where we have a luminance signal and chrominance separated, with the chrominance signal being encoded differently in the two systems. But when we speak of RGB signal, the three color components are separated, There is no encoded chrominance signal. In terms of resolution and refresh rate, PAL-M and NTSC are equal.
  2. The 2600RGB It also has its own color palettes, so that it wouldn't make any difference to original console palette. The chip itself Atari (AUNT) does not produce a RGB signal, which is generated directly by the 2600RGB.

I could, therefore, jeopardize the installation of 2600RGB without making the transcoding. But I had two other good reasons not to try:

  1. The label of the transcoding Polivoks is glued on top of the AUNT, the chip that needs to be removed to install the 2600RGB, in which the AUNT will be bound. Would be difficult to find room under the metal protection from interference to the 2600RGB and also for the plate of Polivoks. At least it would be necessary to put some extensions in the label.
  2. To install 2600RGB you need to unsolder the original crystal oscillator and mount it on the plate, with Struts, so that the 2600RGB don't bump it. If we're going to have to remove the crystal oscillator PAL-M anyway, Why don't you take the opportunity to replace him with a crystal oscillator NTSC?

Despite my motivation has been the 2600RGB, even those who do not will install a against can eventually prefer de-transcode your consoles Atari 2600, for some reasons we will see throughout this article.

Well, before I go into the details of how I did the transcoding, worth telling a little of the history of these color systems and Atari 2600 transcoded to PAL-M by Polivoks. In this way, readers will be able to make a conscious choice for de-transcode or not their consoles. Then I'll discuss the advantages and disadvantages of doing this-transcoding. Por fim, detail the process that ran.

As far as my knowledge, This is the first article on the Internet detailing this process in a Atari 2600 the Polivoks with American Board Rev. 17. There are articles about the Rev. 16 and earlier, and also on the Brazilian plates, but nothing found on the Rev. 17, but also detail further.

The NTSC, PAL and PAL-M

The NTSC system (National Television System Committee) It was created in the US in 1941, originally without color support, and was used for analog TV transmission. The NTSC system uses resolution of 525 lines and 60 image fields per second. The choice for 60 image fields per second was not random. The U.S. power grid works with alternating current teetering on a frequency of 60 Hz. Give way, avoiding flickering in the image.

No Brasil, where we also have a network of energy working on 60 Hz, the NTSC standard was adopted in the broadcasts in black and white, so that American TVs could be used in Brazil without restrictions.

In 1953, a new NTSC standard was created to work with colors. The new system needed to be compatible with the old, so that the black and white TVs continued working with color transmissions, only without displaying colors. So, It was decided to carry the color information (chrominance) on a sub-carrier of 3,579545 MHz, so she could be separated from the chrominance signal by colored televisions, and ignored by black and white televisions.

The vast majority of countries with electricity networks 60 Hz adopted the NTSC standard, including Japan, that uses the NTSC system with minor modifications (NTSC-J). But in Europe the electric power grid works with frequency of 50 Hz, What prevented the adoption of NTSC as he is. So, the PAL system (Phase Alternating Line), initially in Germany, in the early 60.

The PAL system has a lower refresh rate, with 50 image fields per second, and a higher resolution, with 625 lines. Furthermore, the PAL eliminates some problems of NTSC regarding the color rendition. The NTSC TVs need a tint control to compensate for these failures, something dispensable in PAL systems.

The vast majority of countries that use electric power networks 50 Hz adopted PAL systems. Are several variants such as PAL-B, PAL-G, PAL-D, PAL-K, and PAL-I. In South America, Paraguay, Uruguay and Argentina use a system called PAL-N, also with 625 lines and 50 image fields per second.

The natural way to Brazil would adopt the NTSC color system, like other countries with electric network 60 Hz. But instead, the Brazil opted to create your own system: the PAL-M.

Despite the name PAL-M, the Brazilian system is much more like the NTSC than with any of the variants of PAL. It also uses 525 lines and 60 fields per second, while retaining compatibility with the black and white TVs, However the sub-carrier carrying the chrominance signal is 3,575611 MHz. As a result, an NTSC signal appears in black and white in a TV PAL-M, and a PAL-M appears in black and white on a NTSC TV, both with sound.

The PAL-M combines the best of both worlds: the best color rendition of the PAL system with higher refresh rate (60 fields per second) NTSC system. Technically, PAL-M is superior to NTSC and other variations of PAL. Superior to NTSC by accounts of the best color coding and superior to PAL on the higher refresh rate, that provides a more fluid image.

But the motivation for the adoption of the PAL-M was not only the technical superiority. The color TV arrived in Brazil during the military regime, in time of great economic growth and protectionism. The adoption of a unique system made it impossible to import tv sets, What was desirable under the pretext of strengthening national industry. Whilst Brazilian manufacturers took some advantage with this decision, on the other hand the Brazilian TVs also could not be exported, to be incompatible with other systems.

This also ended up applying to video equipment, as video games. Our first VCRs, for example, reproduced NTSC tapes, transcoding the video to PAL-M, because our VHS tapes were distributed in the NTSC system. But, recording TV content the tape was in standard PAL-M. Only subsequently emerged which also reproduced directly in video cassettes NTSC for TVs compatible, and recorded NTSC if the source were NTSC.

Only there for years 90 is that began to appear the Brazilian TVs that work with the NTSC system, In addition to PAL-M. The PAL-N also ended up being incorporated. These changes probably aimed at export to our neighbors in South America. And vice versa in the case of the TVs manufactured in neighbors. It ended up solving the problem with the imported video games. Today we don't have to worry about transcoding, at least in the case of consoles from the USA.

The Atari 2600 PAL-M the Polivoks

The Atari 2600 born in the USA and, of course, work with the NTSC color system. Give way, to bring an Atari for Brazil and call in a brazilian TV, at the end of the year 70 and early 80, the result was a frustrating image in black and white.

For the Atari 2600 work in color in Brazil was need transcodes it to PAL-M. Transcoding to PAL-M consists of making changes to the system, including changes in the Board and component changes, for the system to pass the issue a signal compatible with the PAL-M system.

The first batches of Atari 2600 arrived in Brazil at the hands of retailers of Mappin/Mesbla network. It is said that they supported the transcoding of these consoles to PAL-M and sold the devices already transcoded. I can't say exactly how this transcoding was made, because I've never seen a console of those.

The Atari 2600 came to Brazil officially by the Polivoks. Initially they were importing the plates were ready the U.S. and transcoding in Brazil. Later they began to manufacture their own boards.

The circuit board of the Atari 2600 has undergone several updates over the course of your existence. I can't tell you exactly which revisions have reached Brazil, but I have in hand the review 17 and I have also seen reports of people with the review 16 and the review 13.

On the Islands that saw the review 16, transcoding the Polivoks was made through a plate somewhat large, It was glued on and held virtually all the space on the three CIs major, and under the metal protection. Furthermore, the original crystal oscillator 3,579545 MHz was replaced by a crystal oscillator 4 MHz. Possibly other modifications were made in the Board and components. A picture of this label can be seen in the picture below, taken from the website of the Victor Trucco. She is identified as PCI-317 and connected to the console by 5 fios.

Atari Board 2600, Rev. 16, with transcoding of Polivoks

Atari Board 2600, Rev. 16, with transcoding of Polivoks

In the review 17, the Polivoks has reduced the size of the label of transcoding. She went on to have fewer components and be connected to the motherboard with only 4 fios. Furthermore, the original crystal oscillator 3,579545 MHz became replaced by a crystal oscillator 3,575611 MHz, exactly the subcarrier frequency of PAL-M.

I don't know if the change was just to reduce costs or if there was some other modification, because I believe that I have never seen an Atari 2600 the Rev. 16 transcoded into operation. I don't know if there was any change in the quality of transcoding or color palette.

The label of PAL-M can be seen in the pictures below, of my two Atari Rev. 17. Note that the colors of the wires are different on both consoles.

Atari Board 2600 with the paddle that transcodes to PAL-M the Polivoks

Atari Board 2600 with the paddle that transcodes to PAL-M the Polivoks

Atari Board 2600 with the paddle that transcodes to PAL-M the Polivoks

Atari Board 2600 with the paddle that transcodes to PAL-M the Polivoks

The label of transcoding to PAL-M the Polivoks, glued on top of the AUNT

The label of transcoding to PAL-M the Polivoks, glued on top of the AUNT

The label of transcoding to PAL-M the Polivoks, glued on top of the AUNT

The label of transcoding to PAL-M the Polivoks, glued on top of the AUNT

The label of transcoding to PAL-M the Polivoks, glued on top of the AUNT

The label of transcoding to PAL-M the Polivoks, glued on top of the AUNT

When the Polivoks started to manufacture their own boards, Strangely she kept the label of PAL-M separated instead of incorporating it into the main PCB, as seen in the photos below, taken from the website Pakéquis.

PAL-M Board in Atari 2600 the Polivoks plate

PAL-M Board in Atari 2600 the Polivoks plate

Atari PCB 2600 the Polyvox

Atari PCB 2600 the Polyvox

With little sign of transcoding, or Atari 2600 passes display a signal compatible with the PAL-M system, and displays colors in Brazilian TVs. And that's how we play our Atari 2600 in years 80 and beginning of years 90. But it is worth noting that the fact that a sign be compatible with PAL-M does not imply that the original color palette is preserved. In the case of Atari 2600, the palette generated on systems converted to PAL-M is different. The colors are not the same NTSC system.

I particularly think the colors of PAL-M well uglier, with lighter green pulling Brown, Beige by pressing yellow/orange, medium green getting very dark, pulling red to magenta, among others. Although this has been the palette with which I played in my childhood, I can't like her today.

It is important to note that I am referring to colors generated by transcoding with the plate lower, used in Brazilian and American plate plates Rev. 17. I can't tell you how are the colors with the larger transcoding card, used in Rev. 16 and earlier. She might have different colors.

Worth-transcode the Atari 2600?

As I mentioned earlier, from the mid 90 the Brazilian TVs began to be made compatible with the PAL-M and NTSC systems, so transcoding is no longer needed. But it's worth removing transcoding from an Atari 2600?

Because I have good reasons both to transcode the Atari 2600 back to NTSC and not-transcode, and keep it in PAL-M. I will list them below.

Reasons to keep the Atari 2600 transcoded to PAL-M

  1. The current TVs continue supporting PAL-M. As I mentioned, the TVs manufactured in Brazil since the late 90 already support the NTSC standard and transcoding is no longer needed. But that doesn't mean they are no longer endure the PAL-M. To this day the TVs support and probably will continue supporting the system PAL-M. So it's not really needed-transcode.
  2. Keep the originality. When I speak of install mods It may even seem somewhat ironic that I give value to maintain originality. But the fact is that I like to keep my equipment as they were designed. In my childhood I listened too colleagues say: “If this were my bike/moped I took the stickers.”, “If this was my car I took the ice and let the wheels exposed”. And I was always the guy who disagreed with all of this on the grounds take originality. And don't even talk to me about cars relegated. An engineer spends years to design a comfortable car, insurance, stable… to see a Zé Ruela and demote the car, leaving as comfortable as a wagon. Some argue that de-transcode is to return the console to the originality, After all, the Polivoks who did the modification in the original plate. But on the other hand, the Polivoks was Atari's official representative in Brazil, so any changes that they have made, For more gambiarrenta to be, It's still an official modification. I do mods only when the gain is really great. That's why all my other consoles have never been modified by me. And even in the case of Atari 2600, I still have my other two consoles transcoded, and they will remain so.
  3. Keep the palette PAL-M. As I said earlier, the palette of an Atari 2600 transcoded to PAL-M is different from the original palette. I think the palette PAL-M well ugly, But taste is taste and can be someone like. And there's also the nostalgia factor. Someone may want to play with the same palette that played in childhood. I do not question, but the nostalgic purists, We do not accept play Atari 2600 without being via RF in a TV tube, You may also prefer to keep the palette PAL-M.

Reasons to transcode the Atari 2600, back to NTSC.

  1. Bring back the original palette. The original NTSC palette is much prettier than the palette generated on the Islands transcoded. Nay, She is the palette with which developers have created games. If you want to see the game as they were designed, necessarily need a NTSC palette.
  2. Leave the console as originally designed by Atari. Atari designed the console to work in NTSC. The only difference between an Atari and a Brazilian American plate is made by Polivoks transcoding. Removing the transcoding, the systems are identical. Even the Polivoks casting is faithful to the American housing (Darth Vader model), with the serigraphy in English.
  3. Install mods that require the console in NTSC. As I said, I don't know if this is the case with the 2600RGB, but there are several other mods composite video and S-Video that assume that the system is in NTSC. Trying to apply such mods transcoding systems for PAL-M does not work. So, remove the transcoding becomes a necessary step.

Next Chapter…

Initially it was to be a single article, but as I realized he's getting big, I decided to break into two parts. 🙂

Agora que você já sabe as vantagens e desvantagens de remover a transcodificação, e pode decidir se vale ou não a pena fazer este procedimento. In part 2 deste artigo descreverei com muitos detalhes como removi a transcodificação no meu Atari 2600 the Polivoks with American Board Rev. 17, com resultado excelente. Until then…

Permanent link to this article: https://www.skooterblog.com/2017/09/05/de-transcodificando-atari-2600-rev-17-para-ntsc-polyvox-com-placa-americana-parte-1/

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