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Trellot

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About Trellot

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  1. Afternoon everyone, I've made a final determination of which chip is at fault after gathering the data for the table above. The A105 OS ROM chip for the 400_A system is bad. For Test #4 in the above table, I was able to get a passing set across two systems by swapping the A105 chips into each, however, repeating the swap test over and over resulted in the failure following chip A105 from Atari 400_A more often than not. With this data, I'll be placing an order in for a new one very soon. Happy day to all, ~ Trellot
  2. Evening All, Finally found some time to continue debugging what I started on this posting regarding a non-booting Atari 400 I purchased last year. Previously I was seeing a dark brownish screen at power up and we were able to narrow down the issue to potentially the OS ROM chips. Since my last posting, I was able to acquire another working Atari 400. Below is a table of results on some chip swapping I did to try to segment which chip is bad, or a combination of chips, etc. In the table each chip configuration, per test, is exactly the opposite of the other on each Atari system for clarity. Note_1: 400_A = original failing system which prompted this post; 400_B is the new working system I recently acquired. Note_2: In the table, when I declare a Pass what I mean is that the system boots to Memo Pad...i didn't have the keyboards installed to test for full functionality, FYI. Observation_1: Notice Test #4 where, based on the chip configuration, I found two simultaneous passing configurations causing two working systems...this confuses me since, based on the table, and with all three original ROM chips installed into 400_A the system won't boot; one of the original ROM chips from the Atari 400_A system appears to be bad. Observation_2: on the 400_A side, tests 5,6,7,8 seem to suggest that A105 is the culprit, but then see test #4 on the 400_B side and that chip passes when installed alone. Observation_3: Also notice Test 2,3,4 from 400_B ... it shows a Pass when swapping one 400_A chip at a time into 400_B, effectively declaring all three chips as good...ugg? Let me know if any of you have an insight into this data. Thank you!
  3. A good cleaning and very slight rebending of the copper contacts for good connection should be all you need to do. However, you can purchases replacement switches from http://www.best-electronics-ca.com/ or http://www.myatari.com/ or maybe even www.console5.com.
  4. Ah yes, like the one I ended up fully socketing....with iron and wick....since the bad IC wasn't found until the very last!
  5. I admit this was my first reaction to the pictures as well. Something extra has been done to get that unit so white whether he did a famous job of retrobrighting or he painted it. That fact alone steers me far away from any thoughts of purchase since there should have been some kind of declaration in the description regarding it, imo. And if it is as Gunstar mentioned a lighting trick, then all the more wariness should be employed, lol!
  6. Might want to check back with that previous TIA chip to see whether or not you have two good chips now
  7. Regarding that second games pic, is that Pole Position? If so, there is definitely graphical corruption there, lol. Take a look, closely, at picture 3 of the solder-side of the board. Locate the RIOT chip (A202), first chip on the top, and notice what looks to be potential damage to two traces leading to pins 23 and 24. That might just be some mask coming off, or if say the board was dropped onto something there could be a potentially severed trace there. I'd run continuity on those traces just to rule them out, then move on to next steps. ~ Trellot
  8. Trellot

    No display

    What does the TV show? Snowy screen, solid black? Double check that your switches are cleaned up and making good contact. Try a different RF cable, etc.
  9. Bahhhah! Try Jupiter Lander and Clown Attack! I grew up with VIC 20, not a bad unit. All this mess and then a VIC 20 in the end, I love it!
  10. That connection to C214 looks pretty wild ! I see the pad is gone for pin3 on the rf modulator pinout. Also, the greenish wire connected to the resistor looks to be touching the pad next to it; might just be the pic but good to double check that.
  11. Thanks Nezgar, yeah I will try to acquire more working pieces for this troubleshooting. I like your neat trick here however! I will try it nonetheless once I have a working unit
  12. Thank you for your comment. I'd very much like to try this process. I do have one cart that could be used, such as the one you pictured above. Questions: 1. Can DOS 2.0 virtualization be used for this process? 2. How do I connect the ROM cart to the computer so that the OS sees it? I've dumped spis and such before but through a USB connection. 3. Lastly, as I'm thinking more about this, I feel like I might need a working Atari 400 for this? If so, I guess this test won't work for me yet, lol. Thanks, ~ Trellot
  13. The bad power side board never even powered the LED, it was just dead, I couldn't get any voltage readings anywhere on the 400... it ended up causing my power supply to blow a fuse. I'll try the RAM swapping too. Thanks!
  14. I'm not familiar with the process you're describing above although I understand the value of this test would be to show that the ROMs still dump some kind of data, is that right? So if I were to conduct this test then any data dumped would show the chip to be good? or would I need to compare my dump to some other known good dump out there? Thanks for your reply, btw!
  15. Yes, I will post my findings as I go. Regarding my Atari unit, it does have the stock RAM module inside. I think my next step is to order new populated CPU/RAM boards and play the substitution game. Even if they don't solve my problem I'll at least have a good set for future repair projects.
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