jschaap26 Posted January 8, 2021 Share Posted January 8, 2021 I've got a 99/4A that when powered on outputs black video sustained screech when turned on. I've seen other post about this same problem and have tried what I believe are all the simple fixes including: - Checking the power supply (I've tested the voltages and it's confirmed working for two other 99's) - Removing the cartridge connector - Reseating all the sockets chips - Looking for anything on the board that is damaged I had a spare 9918A and swapping that in but got the same results. I have a logic probe and could run tests (if given VERY specific instructions) but no soldering skills. Thanks in advance for your insights. Quote Link to comment Share on other sites More sharing options...
+chue Posted January 8, 2021 Share Posted January 8, 2021 The BSOD can be caused by a variety of bad chips including: VDP, CPU, RAM (16k), RAM (256b), ROM, GROM. There is a 3 part series on YouTube, in which a guy repairs his: The problem with his TI was the CPU, but that doesn't mean that yours has the same problem. Quote Link to comment Share on other sites More sharing options...
Stuart Posted January 8, 2021 Share Posted January 8, 2021 Personally I'd start by replacing the two MCM6810 RAMs, but you need at least some level of soldering skills to do it. 1 Quote Link to comment Share on other sites More sharing options...
+arcadeshopper Posted January 8, 2021 Share Posted January 8, 2021 check clock, then rams Quote Link to comment Share on other sites More sharing options...
AtariNostalgia Posted January 9, 2021 Share Posted January 9, 2021 I know how you feel. My Beige TI has the same symptoms, but attempting to repair it is too complicated as there are way too many failure points. Quote Link to comment Share on other sites More sharing options...
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