Posted By
TLC
on 2011-08-31
10:42:17
|  Re: Another plus 4 problem
Macc: happy to know that you could get it back into shape... 
MMS: Congrats for buying the machines!
As Macc said, you only have to desolder two wires. Only the shift lock key is soldered (it's in fact a switch), and even that one is pretty simple to (de)solder.
LCD TVs: there are more than one, different issues, when it comes to old computers and LCD displays. These old computers generally aren't typical examples of 100% display standard compliant gears. Odd frame syncing ( = most old computers produce non-interlaced signals, which is in fact not in full accordance of the original tv standards) is usually the first cause of problems... but you can also meet some more specific issues. And all that is beyond the problem of resampling a video signal in general.
The composite video signal of the Plus/4 is not that bad at all; separate luma/chroma (~= s-video) is. From the other hand, the s-video output of the C64 is seriously better (sharp, and negligible crosstalk), but its composite one is slightly problematic. The root of these problems is ultimately the C64's higher dot clock rate, ie. its higher horizontal resolution. Even if you use "non-color" color codes (those with no chroma ie. black and white and grays), say, white characters on black border and paper, there'll already be color artifacts around the sharp edges of the characters, even on CRT displays. Technically speaking, before mixing luma and chroma together (to form composite), luma should be low-pass filtered, so that its high frequency components don't disturb chroma. Here, the high frequency components of the luma signal aren't filtered properly - which is, in turn, due to the dot clock being too high at the first place, and probably due to the fact that such high resolution signal would look blurry, if filtered properly. Some components of the luma signal overlap the frequency domain of the chroma signal - that overlap results in those color artifacts, once the signal is displayed on the screen. Some displays are more forgiving to that, some less (but AFAIK it's always visible, as long as someone uses composite video on a C64). At least, the Plus/4 has an advantage to that, with its lower, more conforming dot clock, and virtually no color artifacts of that sort.
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