Hi everyone. I am hoping someone will recognize the issue I'm having with my Atari 800. I think I've narrowed it down to bad RAM, but before I spend any more money I'd like a second opinion.
The machine was given to me by a friend who had had it in storage for many years. The plastic chassis was destroyed and I had to disassemble and rebuild it, but the PCBs are all intact and the machine started and was able to run BASIC and other cartridge-based software perfectly. I was also able to load a game from cassette a couple times, though the belts in the cassette decks I was sent degraded rapidly and that stopped working.
I recently bought an SD2SIO, and the machine came with an Indus GT. I set to testing these this week, but I can't get anything to load. The specifics of it are peculiar, though.
The SD2SIO is set up to load the menu immediately on startup. When I power on the machine, it hits the SD2SIO, spins for a moment, then loads the menu and shows the files on the card. At that point the machine freezes completely. I have tried every possible input - Ctrl+Arrows in particular - and nothing works. The System Reset button also does nothing, which leads me to suspect the CPU is completely hung. When I first tried this I chalked it up to not knowing how to use the SD2SIO and stowed it for a while.
I received a cable for hooking up the Indus GT and tried it out finally. I have several disks that should be bootable - a couple boxed games, some commercial applications and some user-created disks labeled as applications. In all cases, when I start the machine the Indus sets to work reading the disk and, for several of the titles I've tried, succeeds in getting a title screen up, but then either it prints an error message or corrupt graphics, the machine hangs, or the screen becomes garbled.
Obviously the disks could all be old and tired, but they appear to have been stored well in their original boxes and sleeves and my gut says it's unlikely that they're all bad. The errors are also 100% reproducible, they always fail in exactly the same way for each program. I have cleaned the heads on the Indus.
My hunch is that there's some bad RAM a few kilobytes in - since everything seems to load the application data okay but then fritzes out when trying to load content, I'm guessing there's good RAM where the base program code goes but something's fried up where the bulk data tends to get loaded in. The machine has a 16K stock Atari RAM cart and a 32K third party expansion. I've tried all combinations (just the 16K, just the 32K, and swapping the two) and it just changes the way the errors look.
My assumption is that the 16K RAM cart has a bad chip, that the 32K RAM cart is not wired in a way that lets it correctly replace the 16K (hence testing with that doesn't solve it), and that I just need to get a new 16K card and I should be golden. Let me know if you think I'm on the right track. Thank you! Here's some pics.
SD2SIO (just hangs here)
What happens when I try to load some of the disks I have
What happens when I try to load a couple programs that appear to have error handling
Funky RAM addon