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Member Since 22 Apr 2001
OFFLINE Last Active Today, 12:33 AM

#4280340 Atari 7800 and 2600 Composite Video Mod - Ghosting only on 2600

Posted by Mitch on Thu May 23, 2019 7:57 PM

 I can't recall where I got this pic from, but it has been massively helpful when trying to find where stuff actually is vs the schematics and BOM listings. I wish I had these for the 5200 and other consoles as well.




That would be me. I was in the process of converting it to a cleaner motherboard silkscreen image and making a second one for the other motherboard rev. Never got around to finishing it.

There should be similar motherboard silkscreens in the 2600 and 5200 service manuals.


Somewhat related, I don't think I ever posted a link to this one. http://www.atari7800...xplodedview.jpg




#4278065 Weight of a 7800 Power Supply?

Posted by Mitch on Sun May 19, 2019 7:30 PM

Though it may vary depending on what revision power supply you get. I can think of one that is a bit larger, in size anyway, not sure about weight.


#4267367 OS with Asteroids help!

Posted by Mitch on Tue Apr 30, 2019 12:11 AM

That looks vaguely familiar. I may have one of those boards, still need to take apart some 7800s to check.



#4266507 OS with Asteroids help!

Posted by Mitch on Sun Apr 28, 2019 2:15 PM

The prototype ROM of the Asteroids BIOS that is NTSC only is included as part of the bulk BIOS archive for the A7800 emulator.  It is the file
"c300558-001a.u7" highlighted below:



Looks like you are missing the Pole Position BIOS, the proto NTSC BIOS and the alternate highscore ROM.



#4266002 OS with Asteroids help!

Posted by Mitch on Sat Apr 27, 2019 3:30 PM

The Asteroids BIOS is universal and was designed to work in either PAL or NTSC 7800s. Apparently Atari was planning on shipping it in NTSC 7800s at one point but it never happened. There is a prototype ROM of the Asteroids BIOS that is NTSC only.



#4259760 Hi-res scan of CCII board...

Posted by Mitch on Wed Apr 17, 2019 9:35 AM

Glad you got it working!


#4255070 Here's something cool I found while cleaning

Posted by Mitch on Tue Apr 9, 2019 10:30 PM

That is the Atari Mexico box, only the second one I've seen. What is the serial number on that guy?



#4245777 Baby Pac-Man

Posted by Mitch on Tue Mar 26, 2019 8:23 PM


Almost forgot about that.  That'll be my legacy, when I am dead.  And the only one of it's kind collection, the black MC+ is long gone, yours is the last one.


Hmm, I wonder if I have one of each of those still. I know I have a couple of them.



#4237648 Pal color issue

Posted by Mitch on Wed Mar 13, 2019 8:26 PM

It should also be noted that the PAL 7800 that I was testing on was a PAL RGB model. So the colors might be slightly different than a standard RF PAL 7800.



#4223157 Koolaid Man 2600 incompatibility what other games don't work?

Posted by Mitch on Tue Feb 19, 2019 3:43 PM

Did you check the difficulty switch?


#4207439 USA best place to get scart or BNC adapter

Posted by Mitch on Sun Jan 27, 2019 10:08 PM

Not in the USA but these guys have the cables. https://www.retrogam...cart-cable-cord

Depending on your PVM model:





#4202646 Copy of Galaga 7800 With no Barcode

Posted by Mitch on Mon Jan 21, 2019 3:08 PM

Its an 86 release version. They are all slightly different from the 87 and later releases.



#4201139 Atari 2600 Trak-Ball Games

Posted by Mitch on Sat Jan 19, 2019 3:58 PM

Did anyone ever look at the original Atari Basketball to see if trakball code could be added? Since the arcade game that it is based on used a trakball it would seem to be a good candidate.



#4197644 Crossbow Review!

Posted by Mitch on Mon Jan 14, 2019 8:30 PM

If you want a quick cheat sheet. https://www.atari780...hints/cbmap.jpg



#4193649 Rikki & Vikki

Posted by Mitch on Tue Jan 8, 2019 8:51 PM

This is getting a bit off topic but basically the stock NTSC 7800s have the audio between the TIA and external audio balanced correctly. The PAL 7800s were not balanced correctly because a resistor value was wrong for one of the audio channels. Most people didn't care back in the day because there was only one game that used both TIA and Pokey.

As Crossbow mentioned, most A/V mods for the 7800 have the audio circuit done incorrectly. To do it correctly you can use Crossbow's method if you don't need want the RF output or you can add a 6.8K resistor and 18K resistor. You solder one end of the 6.8K resistor to the lower end of the 6.8K resistor and the 18K resistor to the lower end of the 18K resistor. These are the same R5 and R6 resistors Crossbow mentions above, you then connect the other ends of the resistors and attach it the 10uf cap as Crossbow details above. This will keep the audio intact to the RF modulator as you are basically just duplicating the circuit for the audio output instead of cutting it and redirecting it.