Awoodbridge Posted May 26, 2020 Share Posted May 26, 2020 I have a 400 that I picked up today. It was working great for about an hour. Now if I boot basic/no cart I get a blue screen with keyboard click. The If I boot PacMan I get a black screen and if I start the game just the sprites. I opened it up and reseated the daughter cards, that didn’t work. Quote Link to comment Share on other sites More sharing options...
Sugarland Posted May 26, 2020 Share Posted May 26, 2020 24 minutes ago, Awoodbridge said: I have a 400 that I picked up today. It was working great for about an hour. Now if I boot basic/no cart I get a blue screen with keyboard click. The If I boot PacMan I get a black screen and if I start the game just the sprites. I opened it up and reseated the daughter cards, that didn’t work. Congrats on your pickup. I would try reseating as many chips as possible and using deoxit. Guessing it's a corrosion on chip legs issue. Quote Link to comment Share on other sites More sharing options...
Sugarland Posted May 26, 2020 Share Posted May 26, 2020 Another possibility is that the power supply overvolted the previously working computer. Check your voltages when powered on. Quote Link to comment Share on other sites More sharing options...
Awoodbridge Posted May 26, 2020 Author Share Posted May 26, 2020 Reseating all the chips didn’t work, voltage seems fine. Pokey chip was half out when I went in, but from my understanding is not the issue here. Contact cleaner on the way, there is a lot of oxidation especially on the GTIA. Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted May 26, 2020 Share Posted May 26, 2020 If any games work, but BASIC doesn't, it may be a bad 2K floating-point math ROM- CO12399B .. But you say even without BASIC doesnt work, so it could be many things. RAM? OS ROM's? Chip swap time with another machine... Quote Link to comment Share on other sites More sharing options...
Kyle22 Posted May 27, 2020 Share Posted May 27, 2020 Do any capacitors look swelled up? The tops of them should be flat, not heaved up. Replace any that look bad. This is not too common on 400/800, but it never hurts to look. Quote Link to comment Share on other sites More sharing options...
Awoodbridge Posted June 3, 2020 Author Share Posted June 3, 2020 As a last ditch effort, I swapped RAM chips ABCDEFGH -> EFGHABCD. Now I'm getting a black screen. Is it worth getting a new RAM card? I don't have a donor machine for swapping chips? Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted June 3, 2020 Share Posted June 3, 2020 time for new ram chips or ram card... 1 Quote Link to comment Share on other sites More sharing options...
mimo Posted June 3, 2020 Share Posted June 3, 2020 tf_hh sells a great 48k upgrade and the SCCC is a must have for 400 owners 1 Quote Link to comment Share on other sites More sharing options...
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