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Atari 2600 Jr. one-chip variant UAV install


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Anybody out there manage to get a UAV installed in the 2600 Jr. one-chip variant? I picked this up some time ago for about $20 and was shocked to find it was a single-chip. My initial intention was to see if I could integrate the Janice chip into a 7800 board, and I may do that sometime down the road. For now, I have merely socketed the Janice and added a socket for the embedded game EPROM. I've also recapped it, but other than that, nothing else has been done. If anyone's interested, I can scan these in as 1200DPI PNGs with a flatbed scanner so that the traces can be better documented. Keep in mind that the PNGs will be HUGE (~50MB+).


Note that underneath the RF module shield is NOT a CD4050 but a LM3086 transistor array which is DIP14, so simply plugging in a UAV will not work here. More info on the LM3086 can be found on the attached PDF.

Atari 2600 Jr. Janice Board (Top).jpg

Atari 2600 Jr. Janice Board (Bottom).jpg

LM3086 Transistor Arrays datasheet.pdf

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The signals needed by the UAV mod (3 digital "luma" signals and 1 digital "sync" one), are not available anywhere on a "single chip" junior, as the Janice chip combines those internally and only outputs a single B/W composite video signal on pin 29  (and the color information on pin 31). So the UAV cannot be installed there, although it should be quite easy to obtain a composite and/or s-video signal out of it with a simpler mod.


Here is the pinout of the Janice chip (taken from this Ben Heckendorn's video).


Note that the known "Jan" schematic available online is of an early prototype and doesn't match the production one. The main difference is that the Janice chip in the schamtic is a 48 pin IC, while the one found on the actual 1-chip Jrs is 64 pin. There's also a "Jan Programmers' guide" which also has a pinout for a 48 pin chip, and that  doesn't match the one in the schematic!





So, tracing the board would surely be nice, but a scan of it with the components in place wouldn't help much, as they cover some of the traces. You'd need to

A - remove every single component, taking note of each of them (part number and/or value) and where it goes in the board
B - scan the bare, unpopulated board on both sides.


That's what has been done e.g. here for the SECAM model.


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Augh!! You're right, I should have checked Ben's notes. Thanks for reminding me...


So, looking at the pinouts for the production variant of the Jan, I see pin 12 listed as CLUM and 31 as CCOLOR. Would it be far-fetched to assume that these are "Composite Luminance" and "Composite Color"? If that's the case, then a UAV mod might be possible.

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10 hours ago, XEGS'r said:

Would it be far-fetched to assume that these are "Composite Luminance" and "Composite Color"?

CLUM is indeed composite luma, that is the analog B/W composite video signal I was talking about in the previous post.

CCOLOR is just color( or chroma). "Composite color" doesn't have any meaning. The extra "C" is probably just a typo in labeling the IC pins.


10 hours ago, XEGS'r said:

If that's the case, then a UAV mod might be possible.

No because, as I said in the other post, that analog composite signal is useless for an UAV board, as it needs 3 separate, digital "luma" signals and a digital "sync" one, none of which can be found on a single chip junior.


You can for sure get s-video and/or composite out of that console, but not with an UAV board.
Since the console is quite rare, I'd probably just leave it as is and search a more common 3 chip Jr for modding purposes...

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