27 replies to this topic

[nick3092]

I've noticed on my two 2600's, there is a vertical blue line displayed at what appears to be the edge of the drawing field.  I had never noticed this line on any of my other 2600 compatible systems, and never owned a true (working) 2600 until recently.  I tried searching for anyone else mentioing this, but couldn't really find anyone reporting a similar issue.

 

Long story short, I grew up playing 2600 games on my Colecovision with the expansion module.  Around 16-17 years ago, I also picked up a pair of 7800's and a system changer for my Intv2 that I occasionally played 2600 games on.  I never had a true 2600 until about 8 or 9 years ago someone picked up a 4 switch for me at a yard sale.  But the power switch was broken, so I never used it.  This past spring, I found an original channel 3 only heavy sixer for a good price at the Midwest Gaming Classic, so I bought it.  I decided to repair/refurbish both of them, so I ordered a new power switch for the 4 switch, and two cap/refurbish kits. The 2600's work perfectly, with the exception of the blue vertical line.

 

The line is very evident on the 4 switch (rev 13).  Here is a shot of Moon Patrol, which shows an offset blue line.  The top line is where the aliens stop flying to the left.  Which makes me think that it is drawing it at the edge of the field, and moon patrol's title screen has two separate drawing fields.

 

 

On E.T., the line is perfectly straight all the way up.

 

 

On the H6, the line is there, but not nearly as noticeable.

 

 

On my 7800, the line is non existent.  Same goes for my Coleco expansion module and my Intv2 System Changer.  This picture is from the 7800, I didn't take pictures of the other two.

 

 

I also noticed it on my Harmony cartridge, that the blue line shifts depending on if there is text on the line or if it's a blank line in the game list.  All screen shots above were using my actual Moon Patrol and E.T. cartridges, so it is not an issue limited to just the Harmony either.

 

Is this being caused by a part that is failing or falling out of spec?  The fact that only the 2600's are exhibiting the issue and not the clones or the 7800 makes me think it's something specific to the 2600's circuit design.  All systems are stock (ie, no A/V mods) except for the caps that have been replaced (the e-caps, the usual suspect caps, and the voltage regulator) and I am using the RF out to send the signal straight into the antenna coax (using a length of RG6 quad shield I made up).

 

Has anyone else seen this issue?  Any input is greatly appreciated.

 

Thanks!

 

-Nick

[RamrodHare]

I have the same issue on my  Revision 12, 4 switcher 2600. Mine looks more purple than blue and I also have a green line on the other side. I have AV modded mine and added the "tune-up kit" (caps and voltage regulator, etc.) I was working on the assumption that this line should fall outside of the viewing area on CRT tvs. I hadn't thought to see if my 7800 has the same lines or not. As a matter of fact, I think I mentioned this in one of my threads not too long ago. I don't remember if I got an answer about it or not.

[nick3092]

I have the same issue on my  Revision 12, 4 switcher 2600. Mine looks more purple than blue and I also have a green line on the other side. I have AV modded mine and added the "tune-up kit" (caps and voltage regulator, etc.) I was working on the assumption that this line should fall outside of the viewing area on CRT tvs. I hadn't thought to see if my 7800 has the same lines or not. As a matter of fact, I think I mentioned this in one of my threads not too long ago. I don't remember if I got an answer about it or not.

 

I'm guessing the difference between the line being blue and purple could be due to how the color pot is adjusted.  Could be slightly different between yours and mine.  As for the line not being visible on a CRT, that is possible.  My parents still have a 19" CRT in their basement.  If I get a chance I could take my 4 sw over there and try it.  And looking at Moon Patrol in an emulator, it actually looks like the aliens are flying all the way to the edge of the screen.  I fired it back up in my 4 sw, and sure enough.  When the demo buggy screen flips back and forth, the upper vertical bar is at the edge of the play field.  So in that case, the upper bar could be just off the screen, while the lower bar would be even further off the screen.  I don't see any green bars off to the right though on any of my systems.

 

As for the Harmony, I double checked and the blue line only appears where something is being drawn.  So when the yin-yang comes up, there is only a short section of blue bar on the left in the middle of the screen.  When the menu comes up, there are multiple little short bars only where the text lines are in the menu.  In the blank spaces in between, there is no bar.  Not sure if that helps narrow anything down as to what causes that.

 

The only other true 2600 I have to compare would be a 4 sw rev 14 I did a refresh for on my friend back in Dec.  At the time, I only tested Space Jockey on his.  I don't recall for sure if it had the blue line or not.  But I would have thought i would have noticed it, as I noticed it on mine right away.  And I don't know when I would get a chance to test his out again to see.

 

It does still seem odd though that it only affects true 2600's, and not the clones or the 7800.  I guess it could come down to TIA revision.  As I understand it, Atari did have variations in the manufacturing of the TIA over the years.  That could explain why its worse on the 4 sw than on my 6 sw.

Edited by nick3092, Wed Jun 14, 2017 5:37 AM.

[TheHoboInYourRoom]

The line is just an artifact of the horizontal blank turning off at the beginning of a scanline. It's a dim green for me on my Rev. E 2600 Jr., on a CRT by the way. Wherever it's offset, that tells you that one or more movable objects (players, missiles, ball) is being shifted horizontally with the TIA's HMOVE function; part of HMOVE's (normal) operation is to delay the end of horizontal blank by 8 pixels. Which explains why the offset shows up with the Moon Patrol enemies and Harmony menu text.

 

I don't know of a way to remove it. There are probably slight differences in the video signal amplification between the VCS and 7800, especially since my Junior was made while 7800s were also being made, which probably rules out age as a factor. It would be worth hooking up your 7800 to the CRT too to compare, if you get the chance. The 7800 may exhibit it slightly.

[DrVenkman]

Yep, it's an artifact of the Atari RF circuitry design ... In the days when the 2600 was designed, many color TVs still had fully analog controls; you adjusted screen height, screen width, horizontal and vertical hold, as well as color, contrast and brightness, with little analog knobs or dials. Heck, my main gaming CRT is a 1987 Apple Color Composite monitor with just such a set of controls. Most people had TV overscan set to hid similar fuzziness in the OTA signals so never even saw such artifacts from their game consoles.

[nick3092]

Thanks for the replies.  It's too bad that its just sort of a thing we have to live with.  It would be nice to have a nice clean picture on a modern TV without that line.  And unfortunately, I'm old enough to remember TV's that I grew up with having said adjustments.  I know Atari did make a few revisions to the TIA video output over the years.  On the sixers, the 4050 buffer was part of the output.  Then in revision 14+ they tweaked the resistor values and added diodes to some of the video lines.  And on the 7800, they presumably had to do something different there due to TIA and Maria both being tied together.

 

At least it's not too bright on my heavy 6.  Or I guess I could just use my Coleco with expansion module.  No line shown, and that is how I grew up playing Atari 2600 games.  So it just sort of feels "right" to me.  But I do like the look of the sixer better than the Coleco.  It's just so iconic.

[RamrodHare]

I figured it was something we would have to live with. I'll hook up my 7800 in little while and see if it looks the same, since I can't remember ( I just had it connected a few days ago, shows what happens to our minds as we age.)   I'll tell you though, before I replaced the caps and stuff on my 2600, I really don't think the line was this obvious...

My experience, based on the TVs I have availible, is that I get a much better picture when I'm using the HDTVs than the CRTs. I don't have any noticeable color bleeding on the HDs, but it's horrible on my CRT. I have yet to test my floor model Magnavox TV, since it's a pain to get to. It's so big that I don't have space in my house for it, so I left it at my Father's and it's now used as a table/shelf of sorts.   I'll try my best to get my 7800 hooked up and post the results tonight, unless it slips my mind (as most everything does, especially when to take my medications).

[RamrodHare]

OK, I managed to remember to test my 7800 and sure enough, no lines on the edges. Which also jogged my memory about something. I was sure that my 2600 didn't have any lines until after I installed the new caps and stuff. What I had forgotten about was that I had been playing everything on the 7800. I didn't start using the 2600 again until I installed the tune-up kit. Old age, man it sure sneaks up on ya. Now that that's settled, It would be nice to know what was changed in the hardware to hide the lines. If it was something as simple as a resistor, maybe it could be replicated on the 2600?

 

Of course, It's not that big of a deal I guess. If it really bothered me, I can always just keep using my 7800.

 

Really, the only reason to use the 2600 instead of the 7800 is just because I like the way it looks. I'm not sure how to explain it, but playing a 2600 game with a 7800 sitting in front of me just doesn't feel "right". I kinda feel guilty, like I'm breaking some ancient, unspoken rule.

[nick3092]

Yeah, it would be nice if it was a quick fix.  I was sort of hoping it was as simple as a resistor that drifted in value, since the 6 barely exhibits the issue, but on the 4 the line is very bright.  But sounds like you may have to completely re-engineer the video output to somehow match what is in the 7800.  Or the Coleco expansion or Intv system changer.  But the only schematic you can compare it to is the 7800, as neither the Coleco or Intv schematics are available (that I am aware of).  And who knows what other issues could arise from redesigning the output.  Redesigning that is far beyond my level of expertise in the realm of electronics.

 

And there is another reason to use the 2600 instead of the 7800, other than physical looks.  To me, the color looks so much more washed out on the 7800 than the 2600.  To me my 6 has the best color, the 4 is second best (I added the resistor to the TIA to improve the color when I did the tune up), and the 7800 is the worst.  I know the 7800 lacked the TIA resistor as well.  I thought I saw a thread here once where 1 or 2 people tried adding it to the 7800, but saw no improvement.  So I think the 7800 is just stuck with the washed out colors.

 

I never really did a comparison side by side of the Coleco and Intv colors to the 6.  I'm pretty sure the color pot needs to be adjusted in my Intv unit (I ran the color bar pattern on it a couple months ago and it was off, and the colors in a few games didn't look quite right either).  But when I ran the diag cart in the Coleco the other day, it looked pretty good and so did Pitfall.

Edited by nick3092, Thu Jun 15, 2017 6:01 AM.

[DrVenkman]

So you got me curious how my recently-AV modded(*) Rev 16 4-Switch Woody looks - no line, even with the brightness turned up on the monitor to see if any faint lines show. I used Moon Patrol since it was the game that showed what you're experiencing most obviously.  

 

 

(*) This Woody has one of Bryan's UAV boards in it rather than the stock RF modulator.

[nick3092]

Interesting, thanks for checking.  So to your earlier post, that means it may not be the image coming from the TIA - rather an artifact being generated in the RF circuit?  Although, I know the rev 16 had changes to the sync and luminance lines (resistors added, values changed, diodes added).  There is still a chance that could be part of the "fix".  RamrodHare mentioned in the thread that he has a rev 12 that is AV modded (although no idea if it is the same AV mod or if he yanked the RF modulator or not) and he has the lines.

 

It would be interesting to hear from more people, both with stock revisions and revisions with AV mods with the RF modulator in or out.  Given enough examples, at some point we should be able to prove out that it is in fact something in the RF circuit.

[RamrodHare]

Mine has the standard cheap AV mod and I removed the RF box. I'm going to connect my 2600 to the little CRT I have handy and see if the lines are trimmed off by the screen shape, if they are, then this issue is only going to apply to people who use widescreen TVs. Honestly, I'd rather use a CRT or a 4:3 aspect flatscreen, but I'm having a big issue with color bleeding on the CRT I have here and I can't seem to find a reasonably priced 4:3 flatscreen anywhere.

 

Nick, just to clarify, you are using a widescreen TV, correct? 

[nick3092]

Yeah, I was running it on a 10yr old 50" Sony rear projection HDTV. I suspect a traditional 4:3 CRT will crop the line out. Which would be great if this was 15+ years ago. But the fact of life is, most of us will have to use widescreen LCDs going forward.

And now that you mention it, DrVenkman mentioned that he mainly uses a 4:3 CRT. Assuming that is what he used for his picture above, that most likely explains why there were no lines in his test. Would be interesting if he could repeat the test on a modern display. If I get a chance I'll try and take my 4sw over to my parents house this weekend and test it on the 19" TV in their basement. I'm sure the line will be cropped off when I do.

[DrVenkman]

And now that you mention it, DrVenkman mentioned that he mainly uses a 4:3 CRT. Assuming that is what he used for his picture above, that most likely explains why there were no lines in his test. Would be interesting if he could repeat the test on a modern display.

I’ll do that tonight after work. Both my current HDTV’s still have Composite inputs.

And for that matter, I’m pretty sure both still have legacy NTSC tuners on the coax Cable inputs. I’ll try with my craptastic Vader over RF as well.

[Kosmic Stardust]

These lines are visible on my 4-switcher as well though not as bright. I think fuzzy little artifacts are just part of the VCS picture. It's not obnoxious and really only visible when the black level is set too bright. I like my blacks truly black so I can see the little phosphor trails...

[nick3092]

These lines are visible on my 4-switcher as well though not as bright. I think fuzzy little artifacts are just part of the VCS picture. It's not obnoxious and really only visible when the black level is set too bright. I like my blacks truly black so I can see the little phosphor trails...

What revision is your 4 switch?

[Kosmic Stardust]

What revision is your 4 switch?

4-switch woodgrain, revision 12 motherboard, stock RF running RG6 coax, 820ohm color upgrade on the TIA. At one point I had the black level set too high on my CRT, and I could see all sorts of dark gray noise artifacts in "black" areas on the screen, but has long been fixed. I can still see feint blue outlines on the left hand edge but they are dark and barely visible, unlike the OP.

 

Even with brand new coax with large RF choke inside the console, I still get a small amount of dot crawl on VHF NTSC-2 when displaying solid colors onscreen. FYI, nothing uses VHF1 band in our area since the DTV conversion in 2009 so the noise is probably just in the signal.

[DrVenkman]

I’ll do that tonight after work. Both my current HDTV’s still have Composite inputs.

And for that matter, I’m pretty sure both still have legacy NTSC tuners on the coax Cable inputs. I’ll try with my craptastic Vader over RF as well.

 

Okay, so I did some testing - apologies in advance for the quality of the photos. The TV I tested on (2012-ish Vizio 1080p TV) is in the master bedroom, currently getting full-on late afternoon sun. So there are reflections all over the place. Anyway, as these photos show, this is RF noise at the beginning of each scanline, plain and simple. It's totally invisible on the AV modded machine and frankly pretty bad on the unmodded Rev 16 Vader through RF.

 

First, using a Rev C UAV board from AA user Bryan connected through Composite:

 

 

 

 

Next, an unmodded Rev 16 Vader connected through RF using Channel 2:

 

 

 

[nick3092]

Well, that is a shame that this appears to not be an easily correctable issue (short of A/V modding it and ripping out the RF components).  10-15 years ago I would have just A/V modded it.  But since then I've changed my stance and prefer to keep systems stock.

 

Thanks to everyone for checking and weighing in on it.

[RamrodHare]

Just remember a standard cheap AV like I have, still has these lines, even with the RF components removed from the board and the shielding still in place. Whatever is causing this is somehow corrected with the UAV mod, but not the common AV mods and doesn't seem to have anything to do with RF interference, since mine has no RF components on the board now.

[DrVenkman]

Just remember a standard cheap AV like I have, still has these lines, even with the RF components removed from the board and the shielding still in place. Whatever is causing this is somehow corrected with the UAV mod, but not the common AV mods and doesn't seem to have anything to do with RF interference, since mine has no RF components on the board now.

One difference may be where different mods pick up the video signals. Bryan’s UAV grabs them right off the TIA. The only other signals you need are +5V and ground, plus whenever you choose to pick up audio. Its a great little device and at ~$25, the price is very hard to beat.

[Kosmic Stardust]

 

Next, an unmodded Rev 16 Vader connected through RF using Channel 2:

 

2600_RF_LCDTV.jpg

 

2600_RF_LCDTV2.jpg

 

2600_RF_LCDTV3.jpg

Do bear in mind this is 30+ year old hardware. We are getting cleaner picture today than ever before in the past. Perhaps it's just intrinsic to the system? Your blue lines are barely there compared to the brightness of the picture. To me this isn't a flaw, just a natural artifact of the technology that went into these consoles at the time of manufacture.

 

If people are hot and bothered by relatively minor defects in the video signal output of these old consoles, then maybe they would feel better running a Raspberry Pi box with some USB adapters? These are real hardware with imperfect analog circuits. It's like there's a half pixel bleed on the RF of my 4-switch woodgrain, but I'm not running to the store to buy materials with which to AV mod the sucker. To me, the colors are bright and vibrant, and the slight RF bleed makes a wonderful de-sharpen filter, so the pixels aren't so rectangular and jagged.

 

And truly once one gets absorbed into the game, all these defects tend to melt away anyhow. Just my opin that some of these faults may be inseparable from the hardware in question. I used to think the raw graphics were ugly, now they have a beauty all of their own and I wouldn't want that taken away. It's one reason why I chose to keep my 4-switch stock but with as clean as possible signal feed, and not do the AV mod.

[DrVenkman]

Do bear in mind this is 30+ year old hardware. We are getting cleaner picture today than ever before in the past. Perhaps it's just intrinsic to the system? Your blue lines are barely there compared to the brightness of the picture. To me this isn't a flaw, just a natural artifact of the technology that went into these consoles at the time of manufacture.

Hey, I’m on your team, man.

I’m merely following up on my earlier post noting that RF noise is just what it is, and it’s better or worse on some systems compared to others. The UAV is in a Rev 14 board but since it’s taking TIA signals right off the chip to generate the composite or S-video (which I’m not using on this machine) it’s gonna be about as clean as you can get with analog signals of this type.

The Rev 16 board is from Atari-era cost-cutting - chips soldered directly, not even paying to color the plastic and going for that all-black look ... It’s got worse RF (but nice vibrant color, ironically). Just the nature of the beast. I’ll note though that the Vader looks better through my early-00’s 27” Toshiba TV than this later-era 1080p Vizio. The former was designed to accept analog signals, the latter does it as an afterthought.

[RamrodHare]

 It's one reason why I chose to keep my 4-switch stock but with as clean as possible signal feed, and not do the AV mod.

The next Atari I get will probably be left original, since I haven't seen a significant improvement with the cheap AV mod. The only thing it did was remove the "snow".  I might go back and redo the one I have now, using the UAV mod, since it seems to be a much better option without a lot of added cost.

[cwilkson]

This is due to too much color saturation in the monitor and mismatched black levels in the video signal.  In short, the single edge created by BLANK to BLACK transition looks like a colored pixel to the video decoder.  Depending on the delay vs. the color burst you'll get blue (close to 180 degrees of phase) or green/brown/gold (close to 0 degrees).

 

Solution:  Turn down the color saturation of the TV/monitor.  Of course that creates other issues such as washed out colors, but....there are compromises.