CBM 8032 Garbage on Screen

Joachim Thiemann joachim.thiemann at gmail.com
Sun Feb 4 22:14:15 CST 2007


On 04/02/07, Marvin Johnston <marvin at rain.org> wrote:
> I've got a CBM 8032 that powers up "fine", but the screen is filled with "!" on
> every other character position. When some letters are repeated, they can change,
> i.e. "nnnn" becomes "onon" which seems like (without checking the ASCII charts)
> that the "n" and "!" are ORed to become the "o". Anyone have any ideas what the
> problem might be? Most of the schematics I have are buried someplace, so I
> thought I would start here.

Display RAM problem? Looks like the LSB, could be the UC5 (2114) RAM
chip, the 74LS373 latch whos designation I can't make out on the
schematic... or the UB4 (74LS244) driver... or any number of other
things.

Joe.



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