Strange behaviours with an atari Jr

[Nintenloup]

Hello to all of you, first message here, hope you're all doing well and I hope this is the right place to post this.

 

I wanted to start an atari 2600 collection for a long time and I finally bit the bullet this month so I got myself a lot of 3 atari 2600 and other things and in that lot, there was a Jr. Been playing with it for a couple of days and when I played the game Kool-aid man, after a couple of minutes of gameplay, the game started to behave strangely. The kool-aid sprite just gets stuck in the left corner bouncing infinitely and the score numbers move into one another. If I reset the console, it just get's back at being stuck after the little intro and same happens if I power cycle the console. The score's numbers also get squished together in the game spider fighter. So it doesn't seem to be cartridge related.

 

So I'm wondering, what could be the problem here ? Bad chip ?

 

I've recorded the behavior and have uploaded to youtube if you want to see exactly what's happening when the game plays. At first it looks fine, but after some time, said problems arise :

 

Thank you.

[Thomas Jentzsch]

Both are well known incompatibilities of many Jrs. There is nothing you can do about, except using a fixed ROM (if these exist) from a flash cart.

[+-^CrossBow^-]

As @Thomas Jentzsch mentioned this is a known issue and afflicts quite a few Jr. models and the later made 7800s as well. The issue is the TIA chip. Many revisions of it, but the later made revisions cause an issue with score counter at the top and once the digits start touching (They aren't supposed too), then it registers the collision hit on the player character causing Kool-aid-man to start bouncing everywhere. Replacing the TIA chip with an earlier revision or at least earlier made year from say a 4 switcher woody for instance, would likely correct it. Then again, at that point you might just prefer to use the console you need to get the chip from.

 

[Nintenloup]

Thank you for these answers !

 

At least I have a dark vader 2600 that's 100% working. So I'm glad to know that it's expected behavior on the Jr.

[The Mr. Video]

On 3/26/2022 at 9:53 AM, -^CrossBow^- said:

As @Thomas Jentzsch mentioned this is a known issue and afflicts quite a few Jr. models and the later made 7800s as well. The issue is the TIA chip. Many revisions of it, but the later made revisions cause an issue with score counter at the top and once the digits start touching (They aren't supposed too), then it registers the collision hit on the player character causing Kool-aid-man to start bouncing everywhere. Replacing the TIA chip with an earlier revision or at least earlier made year from say a 4 switcher woody for instance, would likely correct it. Then again, at that point you might just prefer to use the console you need to get the chip from.

 

I've seen the collision glitch happen when I used to play Kool Aid Man on 2600 Online. Does anyone know exactly why later revision TIAs cause the digits to be pushed together and make the game bug out?