vic20 repair problem

From: Nicolas Welte (
Date: 2001-02-21 14:50:43


I have a VIC20CR (PAL) here that gives me a headache. The really big problem
is that all chips except the three LS245 are soldered in and I don't want to
remove them without having an idea of what is bad.

This machine starts up almost fine, the correct amount of RAM is displayed
(even with expansion plugged in), but no IRQs are generated (thus the cursor
is not blinking) and some character colors are messed up, they turn to
purple. After each reset the purple is somewhere else, so it's probably not a
bad color RAM but a bus conflict or something. Maybe even a bad VIC. Oh, the
cursor starts blinking if I apply IRQs with a wire :-)

Any ideas?

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