On 6/10/20 10:03 AM, Istvan Hegedus wrote: > > There's also a small design flaw in all 264 series machines: there is a > ferrite bead in series with the common ground point of the video out > port, which (i.e. the common point that has non-negligible resistance > above the 1-2MHz mark) causes crosstalk between the signals. (This is > the main reason why the separate luma-chroma output image of these > machines looks bad... there is so much crosstalk between luma and chroma > that it introduces visible moire on the image). All in all... if you > want to get rid of a disturbance factor, find and short the FB between > the machine's and the socket's ground. > > The crosstalk is bad on the composite output too. Even using the > Philips CM8833 it is terrible. When I was kid I did not bother, but now > I can see it. > I will try this FB short to see whether it improves signal. It did here, quite a bit. Finally I get a real greyscale image if I use the luma signal as CVBS. Before the fix I got a color picture when doing that. Also the border color is now smooth, before the fix was able to see the color clock in it when using S-Video. Just short the FB with a piece of wire on the underside of the PCB. Easily reversible that way. On the C16 and C116 it's FB13 and on the Plus/4 it's FB7. GerritReceived on 2020-06-11 17:00:03
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