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15

Thank you @Raffzahn for the comment that inspired me to think of something blocking the video signal. The initial problem described in the previous question was that the ZX81 was showing a white screen. I have an old version of the ZX81, so there was doubt about the absence of the back porch in the video signal. This doubt was removed by adding the 555-based ...


15

That portion of the video signal is generated directly by the ULA; early ZX81s just don't generate a back porch, which was seemingly good enough for the majority of televisions but problematic enough to be fixed in a later revision despite the machine's commercial lifetime being only a year. As you've observed, the absence of a back porch causes some ...


9

The garbled screen is normal on startup, but should be replaced by the BASIC screen after a moment. There's a rather detailed troubleshooting guide, including links, at http://www.dasarodesigns.com/projects/troubleshooting-common-problems-with-the-commodore-pet-2001/ I'd suggest that you ignore the spare parts sales pitch at the beginning and work your way ...


5

Possible reasons IMHO could be: Older computers and consoles sometimes do not work with modern TVs. Modern TV needs a more precise TV signal, especially the timing and voltage level, than older TVs. There is a problem in the N64 itself - maybe some passive parts (resistors or capacitors) in the video circuit are degraded by time. It looks like a video ...


4

Workbench 1.2 is known to have some bugs, and it would be better if you could boot into Workbench 1.3 instead. Based on your description, I suspect your mouse could be malfunctioning. It sounds like the left-button might be "sticking", meaning that it registers as pressed after you release it or fails to detect the "click" when you press ...


2

This is anecdotal, so take with a big grain of salt... I have a C-64 power supply that was home-brewed for me by my Dad when I was a kid from the remnants of the original. My Dad, never being one to do anything halfway, did a fantastic job and added a 'voltage adjust dial' and analog meter to the finished supply. This means I can actually dial-down the ...


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