Assuming the serial number is 949 4420, that would mean your 800 was made in the 49th week of 1979, making it a very early model indeed (and one of the oldest on the serial number list linked above). The CTIA and IC dates would seem to confirm the manufacture date. Nice find!
Thanks for the input Zerosquare! I ended up using 3B for sync ground and the other three grounds for the RGB returns. The result is night and day compared to the RF out. Nice, clear picture. I have the output connected to a DVDO iScan HD and from there to my LCD TV.
Thanks Nezgar for the help in converting to standard ROM files and the info from Jac!s page. Interesting that the ROM checker says its a production ROM, I would have assumed the OS is different from the 800XL because when you cold boot the 1400XL into the self test, it talks to you! Does this mean I could swap in the OS from one of my 800XLs and it would have the same result?
I posted some of the story last year when I was asking about the pinout for the power connector, happy to tell it again
I saw an ad in Craigslist for a garage sale that just mentioned Atari stuff. When I showed up, there were some Atari 8-bits and STs on a bench on the side of the garage. The seller told me he was moving and had been a huge Atari collector in the 80s and 90s, but hadnt really used any of it in years. He was going to have several sales to get rid of everything but hadnt yet dug out the bulk of his collection. I made him an offer on a Percom drive and after we talked some more, he said, you know, I have an Atari prototype computer that was never released. Are you interested? Well, of course I was! He invited me to return to his next sale and said hed have to find it before then.
I watched Craigslist like a hawk and went back to his next sale. Sure enough, he brought out a roughly 1200XL sized package wrapped in a large anti-static bag. When we unwrapped it I was staring at a 1400XL with a smooth plastic prototype case and missing name badge. The seller told me he got it from a former Atari employee who advertised it in the newspaper classifieds sometime in the late 80s or early 90s. He also told me the original owner said it needed some work. I dont know if he ever tried to turn it on. After I made a cable to supply the correct power inputs from a PC power supply, the only thing I had to do to get it working was reseat the chips and replace the 1200XL keyboard Mylar.
The seller ended up having several sales after that and eventually sold off rooms full of Atari stuff. I ended up getting some early serial number 1200XL and 600XL plastics, a bag of random ICs including several CTIA chips, an Atari Service banner, and the mysterious Video Chess cartridge I posted about earlier, among other things. I still havent gone through everything, including the piles of magazines and newsletters he gave me.