Thinking of getting a new Atari 800XL board made....

[reifsnyderb]

Well, I just swapped out the crystal.  Brand F🤬🤬🤬🤬🤬🤬G new crystal.  3.579545 Mhz.  Three  F🤬🤬🤬🤬🤬🤬G days of screwing around.

 

This crystal:  https://www.mouser.com/ProductDetail/774-MP036S-E

 

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It now works.

 

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[+scorpio_ny]

Congrats on finding the issue! I can safely say we have all been there when in comes to issues like this.

[reifsnyderb]

5 minutes ago, scorpio_ny said:

Congrats on finding the issue! I can safely say we have all been there when in comes to issues like this.

Well, I would have never suspected the crystal as the computer booted just fine and B/W video worked.  This strongly implied the clock was working correctly and at the correct frequency.  Thanks for suggesting to look there.

 

Dad and I spent around 5 hours, today, talking through the schematic and modifying the schematic so that the voltage levels matched the output of a working 800XL board with 3 transistors on it.  I just swapped out the crystal with the crystal of the donor board and I get color.

Edited November 6, 2023 by reifsnyderb

[+scorpio_ny]

13 minutes ago, reifsnyderb said:

Well, I would have never suspected the crystal as the computer booted just fine and B/W video worked.  This strongly implied the clock was working correctly and at the correct frequency. 
Thanks for suggesting to look there.

I just based it on some research. You stated that your video circuitry is based on the Atari 800 so I searched on AA and found the exact same issue and the resolution for that issue. Glad to be of some help!

Edited November 6, 2023 by scorpio_ny

[reifsnyderb]

Current ACP of the video output....

 

Everything is a little darker, in the picture, than in real life.

 

 

Edit to add, I just noticed the two left columns, 0 and 1, look the same.  It looks like I'll need to do some more adjusting.....

 

 

Edited November 6, 2023 by reifsnyderb

[bfollowell]

Awesome news!

 

I'm sorry that it seems like you wasted your past several days with all the unneeded extra work, but I'm very glad that you finally found the issue and have it working.

 

Congratulations!

 

[Overange]

Well Done  

 

 

My turn next .......  

[reifsnyderb]

Current state of the color circuitry:

 

Not shown is the GTIA chip and 1k hold-up resistor for the signal coming out of pin 21.  The color-in is from pin 21, of the GTIA chip, after the hold-up resistor. 

 

This circuit is a modified color circuit from an 800.  The component numbers are changed.  R56 and R116 were changed.  Originally, R56 was after R116 and was moved before R116 to ground the emitter.  Also, R65 was added to drop the output amplitude of the circuit.

 

Edited November 7, 2023 by reifsnyderb

[+Larry]

This looks really interesting.  Is the display clarity improved for composite and S-video -- say similar to UAV?  How difficult will it be to expand the ram internally?  Using your 320K board would be easy, but then that doesn't allow for PBI add-ons.  But I guess your 1090 remake would take care of the ram expansion.  Do you have a picture of a current board?

[reifsnyderb]

1 hour ago, Larry said:

This looks really interesting.  Is the display clarity improved for composite and S-video -- say similar to UAV?  How difficult will it be to expand the ram internally?  Using your 320K board would be easy, but then that doesn't allow for PBI add-ons.  But I guess your 1090 remake would take care of the ram expansion.  Do you have a picture of a current board?

The display looks the best I've ever seen.  No jailbars, nice display.  I don't know how close it is to UAV.  While I still need to fix a problem with the left-most column as shown in the Atari Control Picture, I might be able to solve that one tonight.  Also, my cable isn't the best nor is my TV.  This board not only has A/V on it's own power rail, but also has a 47uF capacitor sitting right outside the video and right outside the audio sections.  On one of the 130XE upgrades, there is a tantalum capacitor for the Luma summing transistor.  So, I have that capacitor added as well.  It appears to make a difference, as the picture is has some really minor noise unless a resistor separates the tantalum capacitor from the 47uF capacitor.

 

As you can see, I don't have a keyboard connector attached and just use the joystick port for input.  It's enough for basic testing, though.  Given the scarcity of the keyboard connectors, I don't want to add one to a prototype board.  Also, I am going to slightly change the next board revision so the keyboard connector is easier to de-solder.

 

I tested it out with the PBI today and the 1091XL works.  320k works.  The 80 column display works.  So I am rather pleased with that. 

 

While I was really hoping to nail this the first time, it isn't going to happen.  So, there will be a revision 1.1.  I'll make a new thread for it as this thread was really about some quick upgrades and went off in a different direction anyhow.

 

Revision 1.1 upgrades planned:

 

1.  Larger holes for keyboard connector to aid in de-soldering.

2.  All 4 optional configuration jumpers as per original Sweet 16 documents.

3.  All component values labelled on the silk screen to aid in assembly.

4.  ROM Bank diagram labelled on the board for reference when upgrading the flash ROM.

5.  Better layout of power supply section to alleviate crowding.

6.  Light Pen resistor added to resistor network.

7.  Where possible and reasonable, component part numbers labelled.  (i.e.  part number for DB-9 joystick port connectors)

8.  Re-routing of 100nF capacitor in relation to PBI +5VDC.  (100nF capacitor should only be involved with cartridge port, not the PBI)

9.  Thinking about adding solder points to aid with on-board breadboard.  (i.e.  Phi2, etc.)

10.  Thinking about adding small breadboard region or place for chips in RF module area and near SRAM.

11.  Make composite video an option to install additional components to use it.

 

Here is Rev. 1:

 

 

You can see the video section in the middle left....with the component forest sticking up.   🙂

 

 

 

 

Edited November 7, 2023 by reifsnyderb

[+Larry]

Wow!  Two thumbs up!

[+scorpio_ny]

The real test... DOES IT WORK WITH MULE?😄

 

Seriously though, This looks great! A couple of things:

1. If you have not, I would suggest that you test high speed SIO before your next revision since it seems to be very sensitive to timing and voltages.

2. If you plan to leverage the empty spot of the RF modulator area, keep in mind that some video upgrades leverage that spot for the installation video connectors.

3. I am glad that you are including the option for composite video. A lot of games still use artifacting to create its colors. Since you are basing your circuit on the Atari 800, I assume its artifacting behavior will be similar. By adding composite back it, would it degrade the Svideo?

 

[Jfcatari]

Rev 1 looks great!

 

Do you have plans for a github repo with diagrams, BOM's, and generated gerber files?

 

 

Edited November 8, 2023 by Jfcatari

[reifsnyderb]

4 hours ago, scorpio_ny said:

The real test... DOES IT WORK WITH MULE?😄

 

Seriously though, This looks great! A couple of things:

1. If you have not, I would suggest that you test high speed SIO before your next revision since it seems to be very sensitive to timing and voltages.

2. If you plan to leverage the empty spot of the RF modulator area, keep in mind that some video upgrades leverage that spot for the installation video connectors.

3. I am glad that you are including the option for composite video. A lot of games still use artifacting to create its colors. Since you are basing your circuit on the Atari 800, I assume its artifacting behavior will be similar. By adding composite back it, would it degrade the Svideo?

 

I didn't try MULE yet.  I probably won't try it because I'd have to hook up the keyboard connector.

 

A high speed SIO test is a great idea.  I'll flash the ROM with OS 6.1 and give it a try.   🙂

 

I will probably put some sort of chip/breadboard area in the RF modulator area.  However, it will still have the modulator slots so as to install SAVO or something else.

 

Composite will degrade S-Video.  So, I'll make it an option that you don't have to install if you don't want to.

[reifsnyderb]

4 hours ago, Jfcatari said:

Rev 1 looks great!

 

Do you have plans for a github repo with diagrams, BOM's, and generated gerber files?

 

 

I am planning to release schematics, have information on flashing the ROM on the board, and have a BOM that includes notes on the optional components.  At some point, I'll release the KiCAD files.  (I think that releasing just the gerber files is like releasing only the compiled code.  The true source is the complete KiCAD files.)

[reifsnyderb]

Ok.  No matter what I do, I cannot get the two left-hand columns, on ACP, to show up with different hues.  So, I tried it on the 800 and can see a slight difference.  My 600XL, with a heavily modded S-Video circuit, is exactly the same (as far as colors are concerned) as the new board.  So, I got really suspicious and plugged in my original 800XL.  That is my very first computer.  The only mod it has is to add chroma to the monitor port and the removal of a capacitor in the video circuit to disable composite video for cleaner S-Video.  Otherwise, this computer is original.  (Quite frankly, I didn't even want to mod that but I also didn't want to setup RF output with an old TV, either.)  My original 800XL has the exact same color output in ACP.

 

As the new board's Luma circuit is almost identical to the original XL circuit, I am thinking that maybe my TV is the problem.  I am not sure at this point.  The new board has a 33pF blur capacitor as per the 800 spec and is configured with a 10uF tantalum capacitor as per a 130XE mod.  Neither of these Luma changes should create a problem.  So, I am thinking this is probably going to be ok.

 

Here's the Luma circuit:

 

 

Note:  C55 is the capacitor that sits on the only power rail going into the entire video circuit.  So, it also is before the 4050 and color circuit.

 

Edited November 8, 2023 by reifsnyderb

[+scorpio_ny]

6 hours ago, reifsnyderb said:

I didn't try MULE yet.  I probably won't try it because I'd have to hook up the keyboard connector.

For testing, use Robotron: 2084. You can start a game with just a joystick and it has a demo mode if you let it sit.

Edited November 8, 2023 by scorpio_ny

[ClausB]

9 hours ago, reifsnyderb said:

I cannot get the two left-hand columns, on ACP, to show up with different hues.

Not even with brightness and contrast adjustments on the monitor?

[reifsnyderb]

23 minutes ago, ClausB said:

Not even with brightness and contrast adjustments on the monitor?

No

[reifsnyderb]

2 hours ago, ClausB said:

Not even with brightness and contrast adjustments on the monitor?

To follow-up:  I played around with the settings even more.  Still no change.  Other than this one issue, the picture is very nice.  I am also pleased with the sound.

Edited November 8, 2023 by reifsnyderb

[Overange]

Have you been brave to test the Zener Circuit yet ? 🫣

 

For testing the Keyboard this would always be a useful device.

 

I do not think the gerbers have been released for this one, but I am sure I have seen other versions out there?

 

 

 

[Overange]

2 minutes ago, Overange said:

Have you been brave to test the Zener Circuit yet ? 🫣

 

For testing the Keyboard this would always be a useful device.

 

I do not think the gerbers have been released for this one, but I am sure I have seen other versions out there?

 

 

 

Ohhhh.... What about putting the buttons and power led on the main board?

[reifsnyderb]

3 minutes ago, Overange said:

Have you been brave to test the Zener Circuit yet ? 🫣

 

For testing the Keyboard this would always be a useful device.

 

I do not think the gerbers have been released for this one, but I am sure I have seen other versions out there?

 

 

 

 

I haven't tested the Zener yet, no. 

 

The keyboard device looks nice.  However, it has that impossible to find keyboard connector on it, so it would require some sacrifice to make.

 

 

 

[+scorpio_ny]

6 minutes ago, Overange said:

Have you been brave to test the Zener Circuit yet ? 🫣

 

For testing the Keyboard this would always be a useful device.

 

I do not think the gerbers have been released for this one, but I am sure I have seen other versions out there?

 

 

 

Couldn’t one just short the leads per the keyboard matrix in a pinch you needed to start a program?

[reifsnyderb]

Here's the schematic for the memory control, signal control, I/O control, and ROM circuits: