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c0pperdragon / C64-Video-Enhancement

Component video modification for the C64 8-bit computer
MIT License
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Horizontal glitches with VIC-II 6569R3 #36

Open tyristori opened 4 years ago

tyristori commented 4 years ago

I get horizontal glitches with 6569R3. Board is NO. 251137 REV C. Here's a video of the glitch:

https://drive.google.com/file/d/1gpyFiY_BxD6BCISTT9gS2czUl1HwVugZ/view

Problem is solved by installing 47pF capacitor between VIC pins 17 and 20.

c0pperdragon commented 4 years ago

Another user had the same problem with the exact same chip revision. The solution with the 47pF capacitor really seems to be the best cure for this. I keep this issue thread visible in case other users also run into this problem.

c0pperdragon commented 4 years ago

To anyone with a similar problem: Please note that this capacitor should only be used if the VIC really creates a jittery clock signal. First probe the clock signal that goes into the FPGA on pin 20 of the ribbon cable. If the signal is a clean 50% rectangle, the capacitor will probably do more harm to the system stability than help.

c0pperdragon commented 4 years ago

For your interest: 6567R56A is now supported by firmware 2.9.