I've got a real strange Asteroids Board that I'm trying to repair that got me
baffled. Here's the scoop, if anyone has any opinions please let me know.
The boardset is a Rev 4, running on the bench.
The board works fine in self test, perfect picture, no errors are reported. In
game play mode, the board watchdogs. In test all switches beep fine, including
Tilt.
If you disable the watchdog, the game still does not run, only a diagonal
line/outline of screen scrolls on screen.
Fluke 9010 unit verifies RAM OK (long Ram test)
Fluke 9010 unit verifies ALL ROMS checksum ok, in socket. (Also using a know
good set, Rev 2)
Manually loading Vector memory with code to generate a + sign, works fine, and
upon a DMAGO, you get a perfect +. All scope sig's that I have for the + match
just fine.
For Kicks, Isolating the L6-Pin1, does indeed put the game into play mode, but
obviously, you get no screen, restoring the connection results in watchdog's.
I've poked around in the VSM and TIMER for 2 days now, and in Test mode,
everything looks fine.
Any suggestions ?
TomW
It's a long shot, but have you tried swapping out the 6502? I once worked on an Apple IIc computer that worked just fine until you switched to high-resolution graphics mode, then it lost its breakfast. After testing and ruling out everything else, it turned out to be -- of all things -- the microprocessor! I can only guess that its internal means of switching to certain sections of memory weren't working properly.
HTH,
Matt J. McCullar
Arlington, TX
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Received on Tue Oct 31 21:02:51 2000
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