Ti-99/4A reboot and lock up

[Ti-99/4A reboot and lock up]

Hello,

 

I recently acquired a ti-99/4a in somewhat decent condition for not much money, but I'm having an issue with it. On boot, it goes to the software select screen. I don't have a cart, so it only gives me the option to go into TI BASIC (as expected). The problem is, I get to BASIC for about a fraction of a second before the computer soft reboots on its own and then locks up upon the software select screen. Any ideas on where to look for the source of the problem?

[Applied Engineering made Atari RAM expansion daughter cards?]

It should say 37902 I believe.

That it does. So primary worry eliminated, I have a 64k machine with no bad RAM. Not gonna bother upgrading it, since it's looking to be a dealer installed upgrade, so I'd rather keep it that way for aesthetic and historical reasons. Thanks for the help everyone.

[Applied Engineering made Atari RAM expansion daughter cards?]

Okay, so I ran PRINT FRE(0), and got back 37k free. According to the board's amount of 4416s, they should be around 64k. I know that the OS and BASIC take up some of the RAM, but that much?

[Applied Engineering made Atari RAM expansion daughter cards?]

Also both the card and the serial on the 600XL have a year of '83, it might be a dealer upgrade?

[Applied Engineering made Atari RAM expansion daughter cards?]

Well mystery partially solved. Turns out I lied and made up the whole thing (not really, just a case of bad memory and mixing up two different companies because both have the term "engineering" in their name). Here's the photos I promised. As plainly seen, it's not Applied Engineering, it's a company called BOT Engineering.

 

[Applied Engineering made Atari RAM expansion daughter cards?]

Well I figured this is probably the best place to ask. I got an atari 600xl a year and a bit ago, didn't come with a power supply and didn't get one till about 6 months ago. I got some cart games and software to play around with and when I was messing with the self-test, the RAM test kept going for a long time, up to 48 blocks of RAM were tested. Concerned that there was a bad RAM chip, I opened up the machine and discovered a massive Applied Engineering RAM daughter card installed over where the stock RAM would've been. I thought Applied Engineering only produced upgrades for the Apple II, Mac and Amiga machines? I looked up the data sheet for the RAM chip type on the board, and it turns out there's a bunch of 4K chips that add up to 64K total. Can someone shed some light and tell me what the hell have I got? An apple II upgrade that was modified for a 600XL, or an actual AE stock product sold for the 600XL? Will post pics later when I crack the machine open again.