ACML Posted April 16, 2017 Share Posted April 16, 2017 (edited) Had an 800 that was black screen. Turned out that the first ROM chip was bad. Replaced the ROM with one from another 10K OS board. Seemed to work fine. It ran Defender in demo mode for hours. Then I plugged in BASIC, got the normal start up and "READY". Anything I typed in was a syntax error. Things like ?FRE(0) or PRINT "hello". Didn't matter, everything was a syntax error. Put the OS chip back on the board I borrowed it from and installed that in the machine and it worked. So, aren't all OSB ROM chips the same? It did get a checksum error with the mixed chip, but it booted and played Defender???? Are there two OSB versions? The machine was later production, so it shouldn't be OSA ROMs right? Edited April 16, 2017 by ACML Quote Link to comment Share on other sites More sharing options...
Joey Z Posted April 16, 2017 Share Posted April 16, 2017 were the atari C0 numbers on the chips exactly the same? Quote Link to comment Share on other sites More sharing options...
russg Posted April 16, 2017 Share Posted April 16, 2017 (edited) were the atari C0 numbers on the chips exactly the same? Same question. There are three different ROM chips on the board, 399B, 499B and 599B. Maybe your BASIC cart is a problem. Here's a DOS 2.5 with a binary load BASIC. DOS25.ATR Edited April 16, 2017 by russg Quote Link to comment Share on other sites More sharing options...
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