Color pot adjustments for NTSC Atari Computers

[firestorm]

Based on Atari 400/800 Field Service Manual, there is simple way to adjust color pot on NTSC Atari computer without using SALT cartridge. Before you try this please keep your Atari switched on to warm up for 15 minutes.

SETCOLOR 2,1,8 REM CHANGES BACKGROUND COLOR TO 1, PRESS RETURN

SETCOLOR 4,15,8 REM CHANGES FRAME COLOR TO 15, PRESS RETURN

Then adjust Atari color pot to make background and frame around the screen of the same color as possible.

[Chilly Willy]

On my old A400, I just booted Pitfall II and turned the pot until the screen matched the screenshots on the box.

[firestorm]

Try this one it really works and is easy. You need Basic cartridge of course

[firestorm]

Atari document found today sheds new light on color adjustment. Do not use method described by me above because of a small error it creates.

Sorry

 

I will continue my research for correct colors on NTSC Atari computers.

 

http://www.retromicro.com/ficgia.pdfles/atari/8bit/

[firestorm]

Correct NTSC adjustment according CGIA Documentation page 50-51

 

http://www.retromicro.com/files/atari/8bit/cgia.pdf

 

is to make SETCOLOR 2,1,8 look like this for HUE/Phase/Color Balance setting of TV/monitor at 0

 

And SETCOLOR 4,15,8 like that

 

 

 

For Hue/Phase/Color Balance TV/monitor seting correct with Phase -33

 

SETCOLOR 2,1,8

 

 

SETCOLOR 4,15,8

Edited October 4, 2014 by firestorm

[Chilly Willy]

Maybe turn that into a one-page PDF for printing out? That would be handy to have on hand while working on those old systems.

[Kyle22]

I always tuned mine to get the perfect blue on the GR.0 screen.

[firestorm]

Use SALT cartridge, that is the best method.

 

Here you have description

 

 

 

SALT205.rom.bin

SALT 2.05.atr

[firestorm]

Please here is pdf file

Atari_400_800_Field_Service_Manual_June_82 68.pdf

[thorfdbg]

 

Correct NTSC adjustment according CGIA Documentation page 50-51

Likely not. Look, the colors on p.50 are based on the YIQ color space with 601 color primaries. How did you compute the colors here for the forum? The colors here are probably supposed to be displayed according to the HTML standard, which is sRGB based. If the viewers monitors would be calibrated (which is likely not the case), then the colors displayed here would be shown according to the 709 primaries of the sRGB standard, hence an additional conversion from 601 to 709 is likely missing. Likely because I'm not sure how you came to these color values, but as I said, it is a non-trivial business.

[firestorm]

You right thorfdbg, I was in error. Please help to identify and match the colors from description on page 50-51. Any input welcome. I'm searching for correct colors of NTSC Atari.

Atari Field Service Manual Should be the the safe starting point for adjusting color pot.

 

http://www.retromicro.com/files/atari/8bit/cgia.pdf

Edited October 6, 2014 by firestorm