Atari 2600 Field Service Manual questions

[Kirkland]

(Cross posted from here.)

 

Ok, some questions for the experts while I'm muddling through all these flowcharts:

 

1) On section 6-26 of the Atari 2600 FSM, is the 2nd box supposed to be: "Is there -5v at one end" or "Is there +5v at one end"?

Even with my better scan I'm not entirely sure if it's -5v or +5v.

 

2) Which is the most correct way to label the Φ0 and Φ2?  I assume #1, but my last electrical engineering work was 30 years ago.

3) Next questions refer to next/attached image from section 4-7:

3a) Ok, same sorta deal with 0v.. Any complaints about my slashed zero volt in yellow on the right side?

 

3b) middle box: "Is there an open between J201".. should that be "Is there an open trace between J201"?  Unless something else would make it open?? The resolution is to "Repair open trace"

so that seems more fitting.

 

3c) Can anyone explain the reference for "I" in the middle?  No other flowchart references it as far as I can tell.  Section 4-8 is "H", section 4-9 is "J".

Should the "G" in the lower left corner actually be an "I"? Or should that step truly take you back to identifying bad switchboard/motherboard instead of where "I" is?

And if "I" is really a starting point, it wouldn't need a page number- which is why I'm confused.

 

3d) Similarly, is it proper/OK to have two arrows pointing to "A" like I have in blue on the lower right?

Typically, the arrows will run to an existing connection (like the original on the left side) with only one terminating at a symbol.

And if it is OK to have two results hit the same symbol, should I tighten up the arrows to the box for "Swapout A200-A202"

I'm thinking no, but I'm asking for clarification.

 

3e) Yeah, I know referring to other sections should be using the "home plate" symbol instead of a circle.  I'm just trying to maintain some look & feel of the original.

 

** Anyone with an oscilloscope willing to take some pictures of their screens to match what is shown on sections 4-44 and 4-46?

 

Thanks in advance for assisting.

[Kirkland]

More progress, more questions..

 

From section 4-18:

I'll take a wild stab and say "Check for and repair opens between RF module pin 1 and J101 pins 6 and 10 (ground)."

 

And then I'm scratching my head a bit at Section 4-21:

 

At first look, the question on CR200 is asked identically twice in a row.  Now is the 2nd one simply a typo and should just be CR201? (Which is what I think is correct)

OR, (and I'll show my ignorance to subject material here)

After replacing the defective CR200, should it be re-checked, and it there is still a signal, the CR201 is then defective.

but I feel that the lower left "open or shorted trace to diodes" would catch that.  And an extra step like the above should have been mapped appropriately, which is why I lean towards just typo.

[DanBoris]

On 3/22/2024 at 9:06 AM, Kirkland said:

(Cross posted from here.)

 

Ok, some questions for the experts while I'm muddling through all these flowcharts:

 

1) On section 6-26 of the Atari 2600 FSM, is the 2nd box supposed to be: "Is there -5v at one end" or "Is there +5v at one end"?

Even with my better scan I'm not entirely sure if it's -5v or +5v.

Looks like a mistake, it should be +5v.

On 3/22/2024 at 9:06 AM, Kirkland said:

2) Which is the most correct way to label the Φ0 and Φ2?  I assume #1, but my last electrical engineering work was 30 years ago.

#1 is ok. This signal would be pronounced "Phase zero", do you have the Greek letter Phi and then the number zero. 

On 3/22/2024 at 9:06 AM, Kirkland said:

3) Next questions refer to next/attached image from section 4-7:

3a) Ok, same sorta deal with 0v.. Any complaints about my slashed zero volt in yellow on the right side?

Slashed zero is fine, but not really needed since it's unlikely to be confused with a letter O.

On 3/22/2024 at 9:06 AM, Kirkland said:

 

3b) middle box: "Is there an open between J201".. should that be "Is there an open trace between J201"?  Unless something else would make it open?? The resolution is to "Repair open trace"

so that seems more fitting.

Doesn't really matter but "Is there an open" is proper terminology. 

On 3/22/2024 at 9:06 AM, Kirkland said:

 

3c) Can anyone explain the reference for "I" in the middle?  No other flowchart references it as far as I can tell.  Section 4-8 is "H", section 4-9 is "J".

Should the "G" in the lower left corner actually be an "I"? Or should that step truly take you back to identifying bad switchboard/motherboard instead of where "I" is?

And if "I" is really a starting point, it wouldn't need a page number- which is why I'm confused.

Looks like a mistake, I don't see why you would jump back to the point in the troubleshooting. 

On 3/22/2024 at 9:06 AM, Kirkland said:

 

3d) Similarly, is it proper/OK to have two arrows pointing to "A" like I have in blue on the lower right?

Typically, the arrows will run to an existing connection (like the original on the left side) with only one terminating at a symbol.

And if it is OK to have two results hit the same symbol, should I tighten up the arrows to the box for "Swapout A200-A202"

I'm thinking no, but I'm asking for clarification.

Looks like they always tried to have everything that goes back to A be joined to a single A node unless it has to cross another line. Sort makes sense since A is start back the start.

On 3/22/2024 at 9:06 AM, Kirkland said:

 

3e) Yeah, I know referring to other sections should be using the "home plate" symbol instead of a circle.  I'm just trying to maintain some look & feel of the original.

 

** Anyone with an oscilloscope willing to take some pictures of their screens to match what is shown on sections 4-44 and 4-46?

 

Thanks in advance for assisting.

I could take a shot that. 

[DanBoris]

On 3/24/2024 at 11:32 AM, Kirkland said:

More progress, more questions..

 

From section 4-18:

I'll take a wild stab and say "Check for and repair opens between RF module pin 1 and J101 pins 6 and 10 (ground)."

Yes, that seems right. Both pins 6 and 10 on J101 are ground. 

On 3/24/2024 at 11:32 AM, Kirkland said:

 

And then I'm scratching my head a bit at Section 4-21:

 

At first look, the question on CR200 is asked identically twice in a row.  Now is the 2nd one simply a typo and should just be CR201? (Which is what I think is correct)

OR, (and I'll show my ignorance to subject material here)

After replacing the defective CR200, should it be re-checked, and it there is still a signal, the CR201 is then defective.

but I feel that the lower left "open or shorted trace to diodes" would catch that.  And an extra step like the above should have been mapped appropriately, which is why I lean towards just typo.

I think the second block should be CR201, but I also think the yes and no are reversed. If CR200 was for example shorted, it would pull the cathode to ground so you wouldn't get a signal. So if there is No signal it is defective. Same with the second block.

[Kirkland]

Dan, thanks for the input. Always helps to have a knowledgeable 2nd set of eyes.

My big fear was bothering to rebuild 172 pages and then have people shrug their shoulders and say, "It's like Jerzy Soboda's stuff- looks good but there are obvious mistakes, so don't use it"

 

Latest progress attached (made it through the flowcharts of Section 4) 🤯

2600FSM-Test5-4K.pdf

[DanBoris]

3 hours ago, Kirkland said:

Dan, thanks for the input. Always helps to have a knowledgeable 2nd set of eyes.

My big fear was bothering to rebuild 172 pages and then have people shrug their shoulders and say, "It's like Jerzy Soboda's stuff- looks good but there are obvious mistakes, so don't use it"

 

Latest progress attached (made it through the flowcharts of Section 4) 🤯

2600FSM-Test5-4K.pdf 34.49 MB · 0 downloads

Cool project, looks good so far. When I do projects like this I do them for myself, and if other get's benefit all the better. 

 

As we can see, original documents can have mistakes, at least with a new version any mistakes that are found can be corrected to make a better document. 

[+-^CrossBow^-]

On 3/22/2024 at 8:06 AM, Kirkland said:

** Anyone with an oscilloscope willing to take some pictures of their screens to match what is shown on sections 4-44 and 4-46?

 

Thanks in advance for assisting.

Well, I have a period correct B&K 1474 that I use and these were about the best I could grab from it showing those signals and a few other pics to see if these might help? I could get direct screen caps on the STC screens but the color bars screen wouldn't match through an LCD quite right and this was about the best I was able to snap from my little PVM in the lab.

 

Yes, these are adjusted to bring out some of the contrast and lower the brightness down to make them more easy to see. Also some doctoring done to remove glare and background reflections on the tube. Feel free to use these if you want or let me know if you want me to try and get something better?

 

 

 

[Kirkland]

20 hours ago, -^CrossBow^- said:

Well, I have a period correct B&K 1474 that I use and these were about the best I could grab from it showing those signals and a few other pics to see if these might help? I could get direct screen caps on the STC screens but the color bars screen wouldn't match through an LCD quite right and this was about the best I was able to snap from my little PVM in the lab.

 

Yes, these are adjusted to bring out some of the contrast and lower the brightness down to make them more easy to see. Also some doctoring done to remove glare and background reflections on the tube. Feel free to use these if you want or let me know if you want me to try and get something better?

Thanks- these are perfect.  Slotted them right into the oscilloscope and audio test pages.  I'm still a little dicey on the gray bars/color bars test- I've attached what I currently am using- screen grabs slightly modified from this post..

Still need to figure out better replacements for this page:

Atari 2600 Field Service Manual (USA)_098.tif

 

 

 

Atari 2600 Field Service Manual (USA)_096.tif Atari 2600 Field Service Manual (USA)_047.tif Atari 2600 Field Service Manual (USA)_048.tif Atari 2600 Field Service Manual (USA)_049.tif Atari 2600 Field Service Manual (USA)_050.tif Atari 2600 Field Service Manual (USA)_051.tif

Edited March 30 by Kirkland
helps if I include link

[+-^CrossBow^-]

@Kirkland

 

I actually did try and get my scope to show those other readings However, either my scope isn't fast enough or something because I could NOT get my scope to look anything like that. Best I could do was the first diagram where I was kinda getting a square wave from it but it had a very rounded rise and seemed to trail on much longer in time than what those pics show. But, I do wonder if this is because I was using my 7800 with the STC and plugs on it. It was the closest console I had open to be worked on at the time. I will see if I can crack open a 2600 and give it another try later today.

 

[DanBoris]

6 hours ago, Kirkland said:

Thanks- these are perfect.  Slotted them right into the oscilloscope and audio test pages.  I'm still a little dicey on the gray bars/color bars test- I've attached what I currently am using- screen grabs slightly modified from this post..

Still need to figure out better replacements for this page:

Atari 2600 Field Service Manual (USA)_098.tif 413.31 kB · 1 download

 

 

 

Atari 2600 Field Service Manual (USA)_096.tif 1.41 MB · 1 download Atari 2600 Field Service Manual (USA)_047.tif 381.48 kB · 1 download Atari 2600 Field Service Manual (USA)_048.tif 158.81 kB · 1 download Atari 2600 Field Service Manual (USA)_049.tif 353.15 kB · 1 download Atari 2600 Field Service Manual (USA)_050.tif 361.44 kB · 2 downloads Atari 2600 Field Service Manual (USA)_051.tif 566 kB · 1 download

 

For the STC waveforms I would just use what is already there. Unless someone has that cartridge they will not be able to reproduce those wave forms. 

[Trebor]

On 3/29/2024 at 12:53 PM, -^CrossBow^- said:

Yes, these are adjusted to bring out some of the contrast and lower the brightness down to make them more easy to see. Also some doctoring done to remove glare and background reflections on the tube. Feel free to use these if you want or let me know if you want me to try and get something better?

There is something that went wrong with the adjustments and tweaking for the above image.  The purpose is to ensure the color bar above the gray bar and below it are the same color. 

 

The color bar above the gray bar looks good - it is within the golden range if a bit more leaning to a tad more orange-red, as expected when the console warms up,  That color bar represents the $Fx range.

 

The color bar below the gray bar did not turn out as well.  That represent the $1x range - which should be golden(rod). Instead, in that capture, it looks closer to matching the bar that represents the $Dx range.

 

It may just be the screen fresh/flicker at that point, but the whole key and significance of the capture is to represent the two bars adjacent to the gray reference bar should be the same color.

 

 

No where near the nice aspect ratio and overall balance of the above image, but this is closer to how the color bars 'should' appear above and below the gray bar (Which represents the $0x range):

 

 

Here's another example attempt:

 

Any chance of another capture for it?

 

Had a closer look, those who are curious, it leverages $x6 for the luminance of the bars.

 

The order of color bars on the screen is:

$16

$26

$36

$46

$56

$66

$76

$86

$96

$A6

$B6

$C6

$D6

$E6

$F6 "SAME COLOR"

$06 "REFERENCE BAR"

$16 "SAME COLOR"

$26

$36

[+-^CrossBow^-]

27 minutes ago, Trebor said:

There is something that went wrong with the adjustments and tweaking for the above image.  The purpose is to ensure the color bar above the gray bar and below it are the same color. 

 

The color bar above the gray bar looks good - it is within the golden range if a bit more leaning to a tad more orange-red, as expected when the console warms up,  That color bar represents the $Fx range.

 

The color bar below the gray bar did not turn out as well.  That represent the $1x range - which should be golden(rod). Instead, in that capture, it looks closer to matching the bar that represents the $Dx range.

 

It may just be the screen fresh/flicker at that point, but the whole key and significance of the capture is to represent the two bars adjacent to the gray reference bar should be the same color.

 

 

No where near the nice aspect ratio and overall balance of the above image, but this is closer to how the color bars 'should' appear above and below the gray bar (Which represents the $0x range):

 

 

Here's another example attempt:

 

Any chance of another capture for it?

 

Had a closer look, those who are curious, it leverages $x6 for the luminance of the bars.

 

The order of color bars on the screen is:

$16

$26

$36

$46

$56

$66

$76

$86

$96

$A6

$B6

$C6

$D6

$E6

$F6 "SAME COLOR"

$06 "REFERENCE BAR"

$16 "SAME COLOR"

$26

$36

Most likely part of the effect of the adjustment I did on the pic to try and bring out more contrast and remove reflection that was showing up in the tube screen. My PVM is small with only like a 9" screen so I have to be pretty close to it in order to get any pics of it. I could get a direct screen capture but as this 7800 has a UAV in it, the colors wouldn't be quite right anyway especially through modern capture equipment.

 

[Kirkland]

5 hours ago, Trebor said:

 

Had a closer look, those who are curious, it leverages $x6 for the luminance of the bars.

 

The order of color bars on the screen is:

$16

$26

$36

$46

$56

$66

$76

$86

$96

$A6

$B6

$C6

$D6

$E6

$F6 "SAME COLOR"

$06 "REFERENCE BAR"

$16 "SAME COLOR"

$26

$36

I will plead a little bit of ignorance here, but to me that reads as if $F6=$16 to be the "same color".

In section 3-9, the manual states: "R211 (R213 on the 2600A board) should be adjusted so the bars immediately above and below the reference line are within one shade of each other"

so I read that as the color below the reference bar should actually match the top color line, with the line above the bar being the shade before ($F6 vs $16).

I personally think it's worded a little goofy with the results of the "same color" not actually being the same color being expected ("within one shade").

But then in the example you posted, they *are* the same color on a TV screen.

From here I reference this older post using an emulator on an LCD screen (I know, I know), but with colors seemingly accurately displayed as:

$F6 "SAME COLOR"

$06 "REFERENCE BAR"

$16 "SAME COLOR"

...they aren't going to match, are they? But that's LCD digital vs CRT with tweakable luminance, where the representation of the signal is open to manipulation/correction.

Or does adjusting R211/R213 only adjust the output of the lines below the reference bar?  But if you're tweaking "video output" then all the color signals should be tweaked accordingly.

 

Edited March 31 by Kirkland
I am confuse.

[Kirkland]

Continuing on trying to clarify things..

On sections 6-14 and 6-15 at the bottom we get the attached page.

 

It says to Swap A201/A200/A202.. but then is has NO-> go to Signal Tracing Cartridge, or Yes-> go back to the beginning.

After swapping, shouldn't there be another decision box saying "Does this fix [the problem]?"  which would lead to sections D and A, and for this section how would I word that?

Just as "Are gray bars now displayed correctly?"  Seems simple, don't want to be incorrect.

[DanBoris]

3 hours ago, Kirkland said:

Continuing on trying to clarify things..

On sections 6-14 and 6-15 at the bottom we get the attached page.

 

It says to Swap A201/A200/A202.. but then is has NO-> go to Signal Tracing Cartridge, or Yes-> go back to the beginning.

After swapping, shouldn't there be another decision box saying "Does this fix [the problem]?"  which would lead to sections D and A, and for this section how would I word that?

Just as "Are gray bars now displayed correctly?"  Seems simple, don't want to be incorrect.

I would say something like, "swap A201/A200/A202, testing after each, did this fix the problem?"

[Trebor]

On 3/31/2024 at 5:20 AM, Kirkland said:

I will plead a little bit of ignorance here, but to me that reads as if $F6=$16 to be the "same color".

In section 3-9, the manual states: "R211 (R213 on the 2600A board) should be adjusted so the bars immediately above and below the reference line are within one shade of each other"

so I read that as the color below the reference bar should actually match the top color line, with the line above the bar being the shade before ($F6 vs $16).

I personally think it's worded a little goofy with the results of the "same color" not actually being the same color being expected ("within one shade").

But then in the example you posted, they *are* the same color on a TV screen.

From here I reference this older post using an emulator on an LCD screen (I know, I know), but with colors seemingly accurately displayed as:

$F6 "SAME COLOR"

$06 "REFERENCE BAR"

$16 "SAME COLOR"

...they aren't going to match, are they? But that's LCD digital vs CRT with tweakable luminance, where the representation of the signal is open to manipulation/correction.

Or does adjusting R211/R213 only adjust the output of the lines below the reference bar?  But if you're tweaking "video output" then all the color signals should be tweaked accordingly.

 

For all Atari consoles: 2600, 5200, 7800, there are changes to the palette as the system warms up. 

The most significant changes are seen with hues 14 and 15 AKA $Ex and $Fx.  The rest are far more subtle.

 

The jump point is how and when the system color calibration took place.  Ideally, after 1 minute but no more than 2 minutes at most, should this calibration take place after the console has been powered off for at least 15-20 minutes, as it should be initiated when the console is cold.

 

Often when the console is calibrated, ideally, hues $1x and $Fx are set to match each other.

 

Cartridges such as Color Bar Generator Cart, provides instructions which result in a console's color potometer adjustment so that $1x and $Fx match.  This occurs when each adjacent color hues are ~25.7 degrees apart from each other in the respective color space.

 

Hue $1x matching $Fx to the "same color" via color potometer inside the console is the same process for the 7800 Diagnostic Cart as well, when making the "right bar solid" on the lower portion of the screen, which is made up of the luminance $x7 value from hues $1x and $Fx.

 

System warm up adds ~1 to 2 degrees to the value which covers the directions, that the colors should be "within one shade" of each other.  Indeed, this will ultimately be the case, if calibration was done properly under the originally intended CRT display hardware.

 

The issue with the initial chosen picture is that it is not even within one shade, but three shades off, as the bar representing $16 looks like the bar representing $D6, whereas it should look more like, if not exactly as, $F6 as described and pointed out, "same color", in the Field Service Manual.

 

Nonetheless, among the two different notions - same color or within one shade, console warm up, the display device, which has often been manually tweaked and tuned to user preference, as well as the color decoding matrix of that display device, all accounts for differences in the experienced color palette.

 

Still, the Stella Programmer's Guide, provides this description of how the colors 'should' appear:

$0x = Grey

$1x = Gold

$2x = Orange

$3x = Bright Orange

...skipping down...

$Fx = Light Orange.

 

Ideally, this is typically achieved with the adjacent hues spaced ~26.7 degrees apart from each other in the respective color space.  To the naked eye, anything in the range of ~26.2 - 27.2 degrees of space between adjacent hues works as well.

 

If "Light Orange"/$Fx is interpreted to fall between the hues of "Gold"/$1x and "Orange"/$2x, then adjacent hue spacing ultimately needs to fall in the range of greater than ~25.7 degrees, but less than ~27.7 degrees.  This overwhelmingly appears to be the interpretation for NTSC 2600 consoles.

 

Once spacing between adjacent hues reach ~27.7 degrees, then consequently:

$1x and $Ex match.

$2x and $Fx match.

 

If "Light Orange"/$Fx is interpreted to ultimately fall between "Orange"/$2x and "Bright Orange"/$3x, then adjacent hue spacing needs to be greater than ~27.7 degrees.

 

When hue spacing between adjacent hues is less than ~25.7 degrees, then green dominates stronger, if not completely, for both $Ex and $Fx ranges under a CRT. 

 

Under a modern display, this green dominance of $Ex and $Fx will occur if adjacent hues are less than ~26.7 degrees.

 

Though consoles can range as low as ~25.7 and as high as +~27.7 regarding adjacent hue spacing, systems after warming up, typically have a palette in which adjacent hues are within the ~26.7 to ~27.7 spacing bracket.

 

While much depends on when and how the color potometer inside the console was set, this is an overall description:

25.7 degrees is considered "COOL" palette.

26.7 degrees is considered "WARM" palette.

27.7 degrees is considered "HOT" palette.

 

There is an excellent, concise explanation with visuals, and provided game examples, over at 7800.8BitDev.org under Atari 7800 Color Documentation.

 

The mentioned behaviors are the same among the aforementioned three (NTSC) systems. The difference with the 2600, is half the luminance values are available (8) compared to the 5200 and 7800 (which have 16).  Combined with 15 color hues and a greyscale as hue $0x range, is how the 128 color palette of the 2600, and the 256 color palette of the 5200 and 7800 systems, is formed.

 

Best and most common game example to see the change under original console hardware is the ground in 2600 Space Invaders.  It leverages a $Ex value, which when the palette is closer to 25.7, is bright green, when near 26.7 degrees, it looks olive green.  When closer to 27.7 degrees, it appears brown.  The infamous "Fun is Back" commercial, which aired during the late 80's, demonstrates the browner ground color when mentioning and showcasing Space Invaders.

 

While there are color decoding matrix differences between traditional (CRT) and modern (LCD/OLED) displays, the biggest difference between NTSC displays is the hue setting start, or begin, point which impacts the palette.

 

Modern NTSC displays have it typically locked in at ~-57 degrees.  This provisions a chartreuse green look for $1x.

 

Traditional NTSC CRTs typically are set to a default value in the ~-45 to ~-30 degrees range.  This provisions a gold/goldenrod look for $1x.

 

The intended CRT gold color palette/look of $1x is crucial for many games to appear as the programmer intended. 

 

The legendary Pitfall! is one such game, when we see how much the $1x range is used - tree trunks, barrels, Harry's hair, ground layer, underground - all are intended to be in the gold range; a lower/darker luminance value, the more brown, and a higher/brighter luminance value, more yellow in appearance.

 

There should be no hint of "chartreuse green" for hue $1x range:

 

 

Anyhow, in short...

Leverage the Color Tool cartridge or Diagnostic cart to calibrate system colors after ~1 to 2 minutes of the console being powered on from a cold state (Console powered off for at least 15-20 minutes). 

 

When that is performed, adjacent hues will be ~25.7 degrees apart from each other, $1x and $Fx match.  System warm-up adds ~1-2 degrees to the value setting, resulting in adjacent hues being ~26.7 to ~27.7 degrees apart, "within one shade", from each other.

 

The resulting colors provide expected or very near expected colors as listed in the tech docs, when displayed under a CRT.

[Kirkland]

17 hours ago, Trebor said:

 Once spacing between adjacent hues reach ~27.7 degrees, then consequently:

$1x and $Ex match.

$2x and $Fx match.

That was the piece I needed confirmed.  It's what I was thinking, but didn't have the technical reasoning to back up.   
 

...the rest was a fascinating read.

thanks!

 

[Kirkland]

Finally done with all the flowcharts.  Will still tweak some positioning later, but that's minor.

On to section 7..

(Progress attached)

2600FSM-Test8-4K.pdf