Re: vic20 repair problem

From: William Levak (wlevak_at_cyberspace.org)
Date: 2001-02-22 03:47:35

On Wed, 21 Feb 2001, Nicolas Welte wrote:

> Hi,
> 
> 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?

VIC chip
Timing circuits
Address multiplexers

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