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juansolo

Investgating PAL 7800 picture issues (was 7800 RGB Musings)

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Fantastic work, Juan!  Thanks to you and Cleggy for sharing this with the community.  It is appreciated!

 

Regarding tuning the color pot for 7800 mode on NTSC consoles, the Diagnostic Cart ROM can be leveraged...

 

Binary: Diagnostic Test Cartridge (19xx) (Atari) [!].bin With Header: Diagnostic Test Cartridge (19xx) (Atari) [!].a78 

 

When the ROM is started there is an ~8 seconds delay showing a blank screen while it runs the diagnostic.

 

It is available for purchase as a stand alone cart at Best Electronics, or the above files can be used with a flash cart accordingly.

 

Spoiler

Atari 7800 US Diagnostic Cartridge.  Will display a single 7800 Diagnostic 7800 boot up Screen.  Necessary to adjust the 7800 top color pot back to factory color settings.  You plug in the Atari 7800 Diagnostic Cartridge and turn on your Atari 7800 console and wait about 5 to 10 seconds for the 7800 Diagnostic screen to appear.   CB101195 $25.00

 

Ideally, this ROM should be leveraged starting with a console 'cold' (powered off for at least 20 minutes), and tuned within the first 30-90 seconds of the unit being powered on.  All that needs to be done is make the right bar solid.

 

 

 

 

 

Here is a simulation with the color swatches labelled, demonstrating the COOL, WARM, and HOT temperature differences of the system:

 

Atari 7800 Diagnostic - COLD - WARM - HOT.gif

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That'd be super useful, but I assume like the colour bars it's NTSC only. Which is a shame as this machine will be winging it's way back to Mimo shortly when we're done with it and we don't have a flash cart for the 7800 (which would be lovely, I've been watching the Concerto updates for ages hoping...).

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1 hour ago, juansolo said:

That'd be super useful, but I assume like the colour bars it's NTSC only.

The Diagnostic Cart is NTSC only.  However, the principle found with it for tuning the color pot...Matching the colors of $1x and $Fx, under a cold system, within 30-90 seconds of it being powered on...can be used with other color bar/palette ROMs for the 7800. 

 

For example, RevEng's Utility Cart can be utilized under NTSC or PAL, and has the "MATCH COLOR" at the bottom, making it super easy.  Plus there is the added benefit of a slew of tests that are included checking audio, memory, controllers, and more:

 

image.thumb.png.924c716eac90c9f2efda5da01e83114a.png

 

BINARY: 7800 Utility Cart (20161210).bin  WITH HEADER: 7800 Utility Cart (20161210).a78

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8 hours ago, Icelvlan said:

Is there an RGB mod in the works?

Tim Worthington (does the NES, PAL N64 and 2600 RGB mods amongst others) has mentioned he's been working on one for pretty much years now. I'd love it and would be the first down for one (his 2600 RGB mod is magnificent), but given the nature of the 7800 I wouldn't hold out for it.

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SainT just mentioned on Twitter that he's finishing up an RGB solution for the 7800:

 

"I think the RGB mod board is now complete. Last bit of polish then off to get some PCB's made."

 

Pretty exciting news!

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2 hours ago, chicgamer said:

SainT just mentioned on Twitter that he's finishing up an RGB solution for the 7800:

 

"I think the RGB mod board is now complete. Last bit of polish then off to get some PCB's made."

 

Pretty exciting news!

:o

 

Well, it goes without saying I'm in!

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A small amendment to the doc. We picked up an S-Video to RGB box to do some testing with which allowed us to compare the levels of the UAV to the All-In-One mod and found that the MARIA chroma levels were a bit too high. Adding a 1K6 resistor to the Maria Chroma line seems to bring it down to a much nicer level. If you've got an all-in-one mod it's a simple add, just put it on the line on the MARIA chroma in. I've added it to the layouts in the doc anyhow, so if you build the mod on the 2.1 instructions, it's got you covered. This doesn't effect the UAV add-on mods in any way.

 

AntiJackModDoc_v2_1.pdf

Edited by juansolo
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More level tweaking, this time to the TIA chroma, this time an in-line 820R resistor. Again, this only effects the all-in-one mods and not the UAV add on mods. Also it's not mandatory, it's just something we noticed now we can more accurately compare the UAV output to the all-in-one.

AntiJackModDoc_2_2.pdf

Edited by juansolo
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