Video Output: Atari 2600 vs. 7800

[MaximRecoil]

Do any of you who have both a 2600 and a 7800 notice a difference in video characteristics? Mine are both unmodified (thus, RF-only), and they are quite a bit different. My 2600 (which is a "light sixer", model no. CX-2600) has significantly more vibrant/saturated colors than my 7800. They both have the same level of "sharpness" to the video, which is quite good for RF. However, my 2600 has interference, which is especially noticeable on light-colored backgrounds (you can't really see it on black backgrounds, which means you'd never notice it playing Space Invaders, but you'd notice it during the higher levels of Missile Command), while my 7800 has much less visible interference; being closer to direct composite video in appearance.

 

I don't use an RF switch for either console, but rather, an RCA-to-F adapter on the 2600, and an F-to-RCA adapter on the 7800.

 

The 7800 has its OEM AC adapter, while the 2600 has an aftermarket copy of the OEM AC adapter (Model No. DV-9500, 9 VDC, 500 mA, made in Taiwan), which is what came with it (I bought it used a few years ago).

 

I would like to reduce the interference if possible. Does anyone have any ideas how to do so? I was thinking of starting by getting a new OEM AC adaptor from Best Electronics, because I've seen / heard of cheap AC adapters causing interference in other consoles. I was also thinking of replacing all of the electrolytic capacitors.

 

I tried to take a video of both for comparison, but the difference isn't really noticeable because a moiré pattern showed up in the video (which you don't see in real life of course) which obscured the interference patterns.

 

 

 

 

[+save2600]

Differences abound between the output of all the Atari systems. Lots of topics on this if you search, but yes - the 7800 has the weakest RF output of them all unfortunately.

 

Composite and S-video mods will help some, but the 7800's output will still suck comparatively.

[sidney]

I can offer no technical expertise on this at all but I notice that my 2600 has a clearer picture than my 7800 (both through RF and both through the same tv with the same settings- though obviously not at the same time!) I should say though that my 2600 is a jr version, I don't know if that makes a difference.

I find the 2600 sticks to the channel better than the 7800 which needs occasional picture tweaking during play.

[MaximRecoil]

Differences abound between the output of all the Atari systems. Lots of topics on this if you search, but yes - the 7800 has the weakest RF output of them all unfortunately.

 

Composite and S-video mods will help some, but the 7800's output will still suck comparatively.

 

My 7800 is better in terms of interference (it has much less of it), but its colors aren't as good. I'm not concerned about the 7800, but rather, I'd like to reduce the interference on the 2600.

[+save2600]

 

My 7800 is better in terms of interference (it has much less of it), but its colors aren't as good. I'm not concerned about the 7800, but rather, I'd like to reduce the interference on the 2600.

Ensure that both ends of the RF cable are clean and free of oxidation. Inspect and clean the female RF RCA input inside the 2600 too. Sometimes even just reseating the connection helps make better contact.

 

You could also try using a ferrite magnet toward the end of the RF cable to see if that helps. Works wonders usually, but if not, could try replacing your RF cable. If you go that route, keep it as short as possible and stick with a true 75ohm cable that has 100% shielding.

[MaximRecoil]

I took the top of the case off and tried it with the same RG-6 cable (as good as it gets, and this stuff came directly from my local cable TV company) with F-to-RCA adapter that I use for the 7800, and it didn't make a difference.

 

This isn't the type of interference that suggests a bad RF connection, i.e., it is not staticky interference. It is the same type of faint, shadowy, random motion interference that all video sent via RF has to some degree, except it is more prominent than on the Atari 7800, which in turn is more prominent than on a front-loader NES connected with RF (which has the best RF video that I know of, though I don't need to use it because it has AV jacks).

 

You can see it in this video, in the red "ground" area at the bottom of the screen:

 

 

It is far more noticeable when the whole screen is a light color, especially blue, but like I said before, when the screen gets lighter, I get a moire effect in the video recording, which prevents you from seeing the interference patterns.

 

It might be something that is just inherent to the design, like "jailbars" on the U.S. toploader NES. I wish I had a different AC adapter to try, but none of the other ones I have use the same connector.

 

Has anyone else noticed more RF interference with their 2600 than with their 7800?

[MaximRecoil]

I just finished cleaning and testing a lot of 5 Ataris (1 heavy sixer, 2 light sixers, 2 4-switch woodgrain), and they all have more RF interference than my Atari 7800. The heavy sixer seems to have the least amount of it, but still significantly more than my 7800. I would like to know why that is. I wonder if it's because the 7800s motherboard is fully encased in RF shielding while all of the Atari 2600 versions I have are only partially encased (the six-switch versions' motherboards are fully encased, but their "switchboards" aren't).

 

Does anyone know of a specific ferrite choke product that they've seen actual positive results from?

[zylon]

For best results on my Atari units, I use a coaxial cable from an old VCR to connect to TV.

 

http://www.ebay.com/itm/Radioshack-Right-Angle-Adapter-RCA-phono-Male-To-F-connector-female-278-260-/181893437421?hash=item2a59b197ed

 

One of these is great for 2600's if you grind down the tip of the RCA end. Then, just run the coax out like the original RF cable.

[+save2600]

 

Does anyone know of a specific ferrite choke product that they've seen actual positive results from?

 

Ones I use all look like this:

 

http://www.amazon.com/gp/product/B009ENG6TI?keywords=ferrite%20choke&qid=1444521546&ref_=sr_1_1&sr=8-1

[MaximRecoil]

For best results on my Atari units, I use a coaxial cable from an old VCR to connect to TV.

 

http://www.ebay.com/itm/Radioshack-Right-Angle-Adapter-RCA-phono-Male-To-F-connector-female-278-260-/181893437421?hash=item2a59b197ed

 

One of these is great for 2600's if you grind down the tip of the RCA end. Then, just run the coax out like the original RF cable.

 

I tried that about a week ago with 2 different VCRs (a GE and a Zenith, both from the late '80s), and the results were horrible. It looked like a case of bad reception rather than just RF interference, and it looked the same on both VCRs. I didn't think to try an auto channel search with the VCRs; maybe it would have locked onto the 2600's broadcasting frequency better. When connected directly to my TV the reception is perfect (RF interference is a different issue than bad reception).

 

My newly acquired heavy sixer is actually pretty close to my 7800 in terms of the low level of RF interference (and better than my light sixers and 4 switch woodgrain versions), and might even be on par with it. I think the reason the RF interference is normally a little more prominent on the heavy sixer is because the colors are far more saturated than the notoriously dull colors of the 7800, making the RF interference patterns embedded in the color more noticeable. I just tried my heavy sixer with Missile Command with the "TV Type" switch set to B&W, and I can't see any RF interference whatsoever, not even on the medium- and light-colored background levels (which appear as medium and light shades of gray in B&W mode), where they are most prominent in normal color mode.

Edited October 11, 2015 by MaximRecoil

[MaximRecoil]

The RadioShack RF Interference Filter 1500025 is useless; at least in my case anyway. I saw no difference whatsoever when using it. I tried it because I've seen it mentioned a few times here, and there are a lot of reviews saying it helps. Supposedly it is effective on RF interference from 54 to 900 MHz, which should cover most anything (it covers all of the VHF and UHF range), so either this gizmo is nothing more than a placebo, or the RF interference I see is coming from elsewhere.

 

I know it's possible to get a very clean RF picture in my house on my TV, because the RF picture from my NES front-loader and SNES Model 1 is very clean (even though I don't normally use RF with them, because they have composite outputs). They have no perceptible RF interference at all (they could pass for composite), and that's with using an OEM Nintendo automatic RF switch complete with its cable that is so thin that it barely qualifies as coaxial cable. My Sega Genesis Model 1 has clean RF too, though not as clean as the Nintendos. It has a slight amount of perceptible RF interference, but less than my 7800 and any of my six 2600s.

 

So what is Nintendo's secret? I know it isn't their RF switchbox, because I've hooked them up directly with an ordinary coaxial cable with an RCA adapter on one end (the same cable I use with my 7800) and they are just as clean as with their OEM RF switchbox. Since the differing amounts of perceptible RF interference (ranging from none with the Nintendos, to barely perceptible with the Sega, to mild with the 7800 and heavy sixer, to moderate with the light sixers and 4-switchers) doesn't seem to have anything to do with the RF cables, I wonder if it has something to do with the power supplies; not the wall warts themselves (I'm using an OEM wall wart in all cases), but rather, how the power is handled within the consoles' circuits.

Edited October 24, 2015 by MaximRecoil

[covertagenda]

A lot of interference is linked to electrical devices in the home such as badly made power supply's, microwave ovens,wireless routers etc.A lot of cheap devices that people buy nowadays are badly suppressed and cause interference on a lot of different frequency's so trying to eliminate this is quite difficult.Good shielded cable and good connection can clean things up but sometimes the cause can be something in close vicinity and finding it can be quite difficult.

[MaximRecoil]

A lot of interference is linked to electrical devices in the home such as badly made power supply's, microwave ovens,wireless routers etc.A lot of cheap devices that people buy nowadays are badly suppressed and cause interference on a lot of different frequency's so trying to eliminate this is quite difficult.Good shielded cable and good connection can clean things up but sometimes the cause can be something in close vicinity and finding it can be quite difficult.

 

Whatever may be going on in this house with regard to electricity, the fact remains that my NES and SNES deliver an RF signal to the TV which is as perfect as possible (zero perceptible RF interference), and none of my 7 Ataris can do that, which indicates that Nintendo knew something about RF circuitry that Atari didn't (or it indicates that Nintendo was willing to spend money on something that Atari wasn't). Nintendo didn't always hit a homerun though; I have an NES top-loader too, and its RF output is garbage (full of vertical shadowy lines, as anyone who owns one knows), but that was obviously a case of being cheap, given that the top-loader was an "economy version" of the NES.

 

By the way, I just tried connecting my Atari AC adapter to the AC line filter in my Street Fighter II arcade machine (AC line filters are standard equipment in JAMMA cabinets), and it made no difference whatsoever.

Edited October 24, 2015 by MaximRecoil

[Lord Innit]

I've owned four PAL 7800s and all of them have had terrible ghosting. My current one being the best of them. It's still rubbish though.

[covertagenda]

Whatever may be going on in this house with regard to electricity, the fact remains that my NES and SNES deliver an RF signal to the TV which is as perfect as possible (zero perceptible RF interference), and none of my 7 Ataris can do that, which indicates that Nintendo knew something about RF circuitry that Atari didn't (or it indicates that Nintendo was willing to spend money on something that Atari wasn't). Nintendo didn't always hit a homerun though; I have an NES top-loader too, and its RF output is garbage (full of vertical shadowy lines, as anyone who owns one knows).

 

By the way, I just tried connecting my Atari AC adapter to the AC line filter in my Street Fighter II arcade machine (AC line filters are standard equipment in JAMMA cabinets), and it made no difference whatsoever.

I think that Nintendo maybe used better quality components/filters and sheilding in the RF modulators,also I think that shielding requirements were different in the 1980s due to FCC rules changing, although the majority of the main shielding is to protect other devices from anything interference given off.

[MaximRecoil]

I've owned four PAL 7800s and all of them have had terrible ghosting. My current one being the best of them. It's still rubbish though.

 

I get some ghosting on my Ataris, but it isn't all that noticeable. The main thing I get is faint, constant random motion patterns within the color, most noticeable on colors of a medium to light shade. The motion isn't truly random; it most often takes on the form of moving diagonal lines across the screen (not really "lines", because they are subtle, faint, shadowy, and indistinct, but I don't know what other word to use). The RF interference patterns disappear almost entirely when switched to B&W mode (on games which support B&W mode). Also, the RF interference patterns are never visible on a black background (unlike more severe forms of noise like from a weak signal or bad connection, which show up everywhere regardless of color).

[MaximRecoil]

I think that Nintendo maybe used better quality components/filters and sheilding in the RF modulators,also I think that shielding requirements were different in the 1980s due to FCC rules changing, although the majority of the main shielding is to protect other devices from anything interference given off.

 

With regard to the RF shields within the consoles, I've had some strange experiences with those. For example, with a heavy or light sixer (both of which use a thick-walled cast aluminum motherboard enclosure for the shield), I see no difference when testing them without the shield. For a 4-switch, testing without the shield (which is made of thin sheet metal) results in a lot of extra noise in the picture, of the "snow" variety, similar to what you'd see with a weak signal or bad connection. With an NES front-loader, removing the shield makes no difference; the RF signal is just as pristine either way. It is interesting that the NES can send such a clean signal even with the deck seemingly stacked against it (i.e., cheap, thin coaxial cable going into an RF switchbox and no RF shield).

[covertagenda]

 

With regard to the RF shields within the consoles, I'vlayout,,some strange experiences with those. For example, with a heavy or light sixer (both of which use a thick-walled cast aluminum motherboard enclosure for the shield), I see no difference when testing them without the shield. For a 4-switch, testing without the shield (which is made of thin sheet metal) results in a lot of extra noise in the picture, of the "snow" variety, similar to what you'd see with a weak signal or bad connection. With an NES front-loader, removing the shield makes no difference; the RF signal is just as pristine either way. It is interesting that the NES can send such a clean signal even with the deck seemingly stacked against it (i.e., cheap, thin coaxial cable going into an RF switchbox and no RF shield).

A lot of interference can also be eliminated by good circuit board design such as good quality board layout,component placement and keeping the power side of the device shielded from the main components.As for shield materials steel works well and does not need to be thick whereas aluminum needs to be made thicker due to its electrical property's. Also some of the shielding is to stop radiation out of the device so that would explain why removing some makes no difference and others make a substantial difference.

[+Mitch]

The tuning can also get slightly off on these old systems. You can adjust it with a plastic hex/allen wrench.

 

Mitch

[MaximRecoil]

It doesn't seem like a tuning issue to me; the signal seems plenty strong, and in a static screenshot you'd never even notice the EMI patterns, because they are so subtle that you only notice them because they are in motion (I posted some screenshots from a few of my Ataris in this thread). Plus, all of my Ataris (and both of my Sega Genesis Model 1s) have it to one degree or another, and I wouldn't think they would all be out of tune. From best to worst:

 

Sega Genesis Model 1 (both of them are the same)

Atari 7800 (I only have one)

Atari 2600 "heavy sixer" (I only have one)

Atari 2600 "light sixer" and 4-switch woodgrain (I have 3 of the former and 2 of the latter; they are all about the same in terms of EMI)

 

The only consoles with RF output I have which have no perceptible EMI are my NES front-loaders (3 of them) and my SNES Model 1s (2 of them). Ironically, that perfect RF output goes to waste because I use composite with them.

 

Then of course, at the bottom of the barrel is my NES top-loader with its notorious "jailbars".

 

I had a ColecoVision for a short while when I was a kid, and I remember that having a noisier picture than my 2600 "Vader".

 

By the way, I tried the RF cable that came with some Atari 8-bit computers, which looks like this:

 

 

It has a ferrite choke in that plastic box, and some people on here have said it works wonders, giving a composite-like picture. Well, in my case, it made no difference whatsoever. This supports my belief that the EMI isn't getting in via the RF cable in the first place, since no matter what I've tried for cables and filters and chokes, makes no difference at all. As I said before, I think it is a byproduct that's inherent to the design of the Atari's internal circuitry.

[SIO2]

 

...

It has a ferrite choke in that plastic box, and some people on here have said it works wonders, giving a composite-like picture. Well, in my case, it made no difference whatsoever. This supports my belief that the EMI isn't getting in via the RF cable in the first place, since no matter what I've tried for cables and filters and chokes, makes no difference at all. As I said before, I think it is a byproduct that's inherent to the design of the Atari's internal circuitry.

Or manufacturing variance on a marginal RFU design.

 

I have seen a lot of variance in performance between like models.

 

Oddly the best RF picture quality I have ever seen from an Atari was on a particular 2600jr I owned.

Edited October 26, 2015 by SIO2

[maiki]

I have noticed that not only the console itself, but also the TV you are using affects the quality of RF signal. I have now 2 portable CRT TVs: Philips and Luxtronic. When I connect my Junior to Luxtronic, there are often horizontal linels flying around (interference). It does not happen on Philips TV though. But, if I connect my Junior to indoor antenna box (set to minimum-no gain) that leads to Luxtronic TV, the RF signal is fine.

 

So this leads me to this question:

 

Is there a device (or rather a small component) that will filter off the RF interference? I know I can use my indoor antenna box but I would prefer a more compact solution.

[MaximRecoil]

Or manufacturing variance on a marginal RFU design.

 

I have seen a lot of variance in performance between like models.

 

Oddly the best RF picture quality I have ever seen from an Atari was on a particular 2600jr I owned.

 

Has anyone ever examined the NES front-loader circuitry to figure out why its RF output is so clean? I don't know enough about electrical engineering to figure something like that out. It would be nice if there were a way to modify a 2600 to have the same clean RF output that an NES has.