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confusedyeti

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Posts posted by confusedyeti

  1. Posted

    12 minutes ago, napabar said:

    I think he was speaking merely of the connectors...not Atari game compatibility.  

    Yep

    4 minutes ago, carlsson said:

    Those use DE-9 connectors, but are wired with a serial protocol so same as NES/Famicom but different connector. I've got a controller from one of those, a Mebetech which there are pinouts for on the Internet. Since I don't have the console and the value probably is $3 or so, I thought about rewiring it for something else but haven't got to investigate.

    Interesting. I've seen those things across Amazon, Aliexpress, etc and thought it weird that they had the DE-9 connectors and I've also seen the controllers alone and thought maybe it might be an option for a d-pad controller for my retro computers that use the port(or have an adapter for the port) with out having to kill an existing controllers to get the actual controller itself and the connector or having mangle on of my Sega controllers to make it safe for the C64(and possibly others?). Though I guess needing a rewire wouldn't be much more work than changing the connector and these controllers at least have the benefit of coming with the parts I need.

  3. Posted

    5 hours ago, confusedyeti said:

    So either I've got a ton of bad RAM or it's not the RAM

    I should have known that sentence was going to come back and bite me. One of the collections of RAM was some I had bought to upgrade my CoCo 2 to 64k and since I had hit a dead end with the Atari I figured I'd go ahead and do that. As you may have guessed by now, it didn't go smoothly. Garbled characters and all that you might expect with bad RAM. So now I went back to my Compaq's RAM expansion and grabbed RAM from the second bank I didn't(used the first in the Atari) and it worked. So with a known good computer, I went through each chip one at a time and found two bad among the CoCo bound RAM that I tested with the most and one in the Atari RAM. Previously I had swapped out the Atari RAM with one at a time, but I must have been using one of the bad chips. Did confirm that the original CPU was bad though and both GTIAs I have work. I'd already ordered another ANITC on eBay just in case, and I won't mind having extra custom chips for these old computers. Now I have a problem with the keyboard, but the thing is filthy, so I'm not entirely surprised there, but it seems to work otherwise, the self tests other than keyboard passed with flying colors and it boots into BASIC and Star Raiders

    • Like 1

  5. Posted

    I've got an Atari 800XL recently(it was tested/working, yeah right) and to start off with it had a black screen and very occasionally a tone would play and occasionally a color would flash on the screen(mostly commonly either red, yellow and I think brown). The old CPU got pretty hot. I tried the Star Raiders cartridge, and it still didn't do anything. Could not get into the diagnostics while holding down option. So spare parts I had for the socketed chips were RAM(I think is good), A CPU and GTIA. After I changed the CPU, I get different results and some times I still get a black screen, but on Star Raiders I will either get garbage output(either with a dark red/brownish back ground or blue) and the most common is it'll say NOVICE MISSION with some @'s in there. Without a cartridge it's either a black screen or a light blue screen with nothing on it, not even a cursor. Still can't get into diagnostics. The new CPU doesn't get as hot.

     

    Since the blue screen was common enough and the service manual indicated it was a problem with U2, I did replace that chip, but nothing changed. I also replaced the GTIA with another one with no change. I've rotated out the RAM with two different sets. I've got the 12296 ANTIC, so from what I understand I'll need RAM with a 128 cycle refresh. What it comes with is NEC D4164C-3. The first I replaced it with was Samsung KM4164B-15, which I think should work by the specs and I'm pretty sure is good(it came out of the memory expansion card in my Compaq Portable that I've noticed no memory issues with), but nothing changes. Though since it behaves differently with every boot, it's hard to tell if swapping the memory or moving it around really has an effect. I also have some KM4164A-15 lying around that I tired(can't find a datasheet, so don't know how compatible it is), but it functions the same as the other sets of RAM. So either I've got a ton of bad RAM or it's not the RAM. Curiously one of the capacitors next tot he RAM, C40, was cut(weirdly the capacitor was cut not just the leg). I've replace it and tried with and without to no change either.

     

    All the chips seem to be getting the right voltage. I used a logic probe and compared to the chart in the Atari 800XL version of Sam's Computerfacts and I've attached a spread sheet that shows results from those in the chart across many chips(if a chip isn't on there, it checked out fine). I'll be honest, I'm a bit out of my depth here and I have no idea which of these chips might legitimately be misbehaving vs which ones aren't working right because they're getting bad signals from a bad chip. I'm pretty sure my first CPU was actually bad because I went from nothing happening at all to at least something happening, but I'm not sure if the new one is bad too, just differently, of if there are multiple faults.

    800xllogic.xlsx

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