ITC#53 - Atari 7800: Compatibility Issues & Capacitor #64

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In this video I go over just a few symptoms that some 7800s exhibit that aren't quite compatible the with the full Atari 2600 library of games. It basically comes down to an added set of components that were added in later models that broke the compatibility with many earlier 2600 title games.
Since making this video I have found out that the 2600 version of Kung Fu Master will also NO longer work when you disable this circuit and the are reports of the 2600 version of Double Dragon no longer working either. However, I've not been able to confirm the Double Dragon side of it as my copy of the game still seems to work when I've tested this.
Video marked as "Not made for kids" due to content is intended for more mature age groups, adults, and those with some basic electronics knowledge and skill.

Опубликовано:

16 дек 2018

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Комментарии : 5

@IvoryTowerCollections 2 года назад

Since making this video, I have also learned that the 2600 version of the game Kung Fu Master is affected negatively by removing the capacitor from the circuit. I've heard reports of the 2600 version of Double Dragon also being effected but haven't ran into that personally. So there are some later made 2600 games that are impacted negatively when you disable the extra timing circuit, but of the games I'm aware of, they all have better versions for the 7800 that are not affected and can be played.

@KeonAureii 3 года назад

I never had issues with Dark Chambers 2600 in my 7800 (NTSC) as far as I remember, but I had image rolling issues with Desert Falcon 2600. Now, if in my Atari 7800 Dark Chambers 2600 works as always, it means that I don't need to mod my console?

@IvoryTowerCollections 3 года назад

If 2600 Dark Chambers is working for you and also the troublesome Activision games like Robot Tank, Space Shuttle, then you are likely fine and do NOT need to worry about this. But it is a common issue I find on many of the 7800s that I've serviced over the years so by default, I've started to lift one leg of the cap out of circuit to prevent these issues when I find them.

@KeonAureii 3 года назад

@@IvoryTowerCollections I checked my 7800 circuit board. It hasn't the C64 capacitor and there's something that looks like a resistor with a single black band instead the 4-color bands on the IC place next to C65 (there's no C65 actually). So I can confirm that I can play those Starpath Supercharger games and 2600 Dark Chambers.

@KeonAureii Год назад

Update note: I have 2 Atari 7800, one is broken (I call it Model A), the other works fine (almost, has few issues, I call it Model B). Both have C025233-002 REV. B boards, Model A is from Taiwan, Model B from China. The thing in common they have is the lack of C64 and C65 caps, and U13 (74LS02), and a jumper on pins 2 and 4 of U13. And both can play Dark Chambers 2600 (Confirmed this on Model A in 1988, on Model B in 2023). The only difference is Model A has a capacitor placed below U2 (6502C) on pin 25 and GND. Model B has no such capacitor. Model B has a weird behavior that shows when a Joystick on Port 1 is connected. On 7800 mode, by pressing any fire button it distorts the TIA sound (but not POKEY), but if you use a 2600 joystick, no weird sound cause it has no 560 ohm resistor, contact between pins 6 and 8. On 2600 mode, when a 7800 joystick is connected, it shifts the colors a little bit to the right of its respective trimpot, and a bit more when pressing LEFT fire button, a bit less with RIGHT fire button, but no distortion in sound, releasing any fire button, colors goes back to the position when only connected, and when the joystick is disconnected, the colors go back to normal (by normal I mean the actual position of the trimpot). If you connect a 2600 joystick (e.g. CX-40) or a custom joystick, none of that weird behavior occurs. Connecting a Sega Genesis 6-Button-third-party gamepad goes on "ape-shit mode" (explained by the presence of +5V), horizontal lines distorting and affecting sprites on screen. Connecting ANYTHING on Joystick Port 2 on any 2600/7800 game has no effect whatsoever, this is only particular of Joystick Port 1. Anyway, that's the summary of the weird behavior my main console (Mod. B) has and I tried to explain on your livestreams.