Yet Another 2600 Composite Mod Help Thread

[Yet Another 2600 Composite Mod Help Thread]

I'm attempting to mod my Sunnyvale Heavy Sixer with a composite video mod. I'm following the quick and dirty single transistor composite video amplifier mod, the schematic is attached. I've built it twice with two different transistors to rule out the possibility of bad parts. I've removed the RF modulator and I'm attaching this amp to the composite video pin that used to go the RF modulator.

 

So far I've removed Q202, R213, and the large pink inductor near Q202. On the screen, I'm getting a dark black snow and the TV think's it's a PAL video signal (it's an NTSC Atari). I've also posted the composite video waveform I've captured with my scope. Without the mod, it's about 1.2V peak to peak and the horizontal blank looks like a fang rather than a rectangle.

NewFile9.bmp

NewFile11.bmp

NewFile10.bmp

 

With the mod, for some reason the signal becomes less pronounced, at about 200mV peak to peak.

NewFile12.bmp

 

This is what my main board looks like right now

 

I should also note that on the secondary board of the Atari (the one with all the switches and the RF modulator), my RF modulator only has 3 pins. All the tutorials I've found online show an RF modulator with 5 pins. The 3 pins on mine are +5V, GND, and (I assume) composite video.

 

Can anyone help me with this mod? Did I forget to remove a component from the main board or something?

 

[Possible Frostbite Prototype Cart?]

We dumped the ROM. There's no difference in the final code. I'm going to be selling this cart off, I'm not much of a collector anymore and I need money for the NX. Still, it was cool to hold a piece of Atari history in my hands.

[Possible Frostbite Prototype Cart?]

The ice flow direction changes when you press fire while standing on it in the final game. Them changing direction when jumping on them sound more like a bug to me than a WIP.

Also I find the aweful noise surprising. In my previews/WIP-demos muting audio-output would be the first thing to do. Weird.

I wasn't aware of that. I just played it on emulator and the igloo parts also disappear when you change the direction of the ice floes. The "glitches" I saw could easily be explained with a faulty controller or system.

...because it's not...

Perhaps I got a bit too excited too quickly. All this info (ice floes changing direction in the final game, the bad audio, and the mask ROM) means it's not a WIP game. I'd still like to get it dumped, but my hopes are down. Sorry if I excited anybody. I've included a picture of the top of the chip.

[Possible Frostbite Prototype Cart?]

If the ice flow speed was a variable, then just changing a single bit (the top bit) could. I don't think it's bit rot, but just pointing out that your comment about this requiring a "total change in program logic" is not necessarily true. Single-bit changes could easily change the direction of objects.

Yeah, that's totally right. Your experience trumps mine lol.

 

Another thing, the game appears to be on either a mask ROM or an EEPROM, it lacks the window that EPROMs have. From what I heard, bit rot is nigh impossible on mask ROMs, and I don't think EEPROMs were widely used in the early 80s. Then again, why would Activision put a WIP game on a mask ROM?

[Possible Frostbite Prototype Cart?]

I can't be sure if it's bit rot but I'm pretty darn sure it's not dirty contacts. When I took the game apart I cleaned them with rubbing alcohol and they're in great shape. Wouldn't bit rot cause more substantial problems, or at least different problems than the ones I'm seeing? From my amateur Atari 2600 programming experience, things like the ice floes reversing direction are a total change in program logic which is unlikely to be caused by bit rot. The only way to know for sure at this point would be to dump it.

[Possible Frostbite Prototype Cart?]

It appears to be a work in progress prototype . I played it on a 2600 today and there are some differences from the final game. There's no sound, only static. There appears to be some kind of glitch where the ice blocks that form the igloo disappear at random and make it impossible to complete the stages. Also, sometimes the direction the ice floes move changes when you land on them, and to my knowledge this doesn't appear in the final game. I'm sure there are other subtle differences that Frostbite experts will notice, I've included a link to a gameplay video below.

 

If anybody knows someone that can dump this, please PM me. Video game preservation is very important to me and I want to get this ROM preserved. I might know someone in my area that can do it but it's not a sure thing.

 

https://vid.me/ZLat

[Possible Frostbite Prototype Cart?]

Matt (Tempest here) might be interested in adding this to his site:

 

http://www.atariprotos.com/2600/software/2600software.htm#F

Thank you, I'll be sure to contact him. My first priority is getting the ROM dumped. I got the cart open (very carefully, making sure nothing was damaged) and I'd like to use my EEPROM reader to dump the ROM. This is the model I have: https://www.amazon.com/gp/product/B00K756PB6/ref=as_li_ss_tl?ie=UTF8&psc=1&linkCode=ll1&tag=atariage&linkId=056a3450b7f0688088832b7804ee6db5

 

What kind of chip do the 2600 carts use? Any other info on how to dump it?

[Possible Frostbite Prototype Cart?]

I recently acquired an Atari 2600 cart from a friend that appears to be a prototype of the game Frostbite. I've only found one other image online of a similar cart, but with no other information besides the picture. This appears to be a different cart because the circles around the R and C are different and the top border of the label is blue while mine is purple.

https://meta2600.com/2016/08/15/frostbite-prototype/

 

Unfortunately I don't have an Atari to play it on, but I'm working on it. I'd love to get the game dumped for archival and preservation purposes. Does anybody have any more information on this cartridge?