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Originally Posted by Penthode
This prototype I find incredibly interesting in light of the early development of the NTSC standard. Certainly, it should be possible to generate a 1952 CPA signal to run the set. I would certainly hope that the set not be modified from the CPA design if it indeed is still a CPA receiver.
Is the subcarrier crystal 3.89MHz?
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*sigh*
If
only there had been a crystal installed in the chassis, it would have made the mystery of what standard this chassis uses a lot easier to figure out that's for sure! Since it didn't have one though, the best I can do is trace the circuit and try to determin if it's still CPA or if it was converted to use the later 3.58MHz subcarrier. I'm still leaning towards CPA though, considering the 'CPA transformer' is the one that's still connected.
Quote:
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CPA at field rate as opposed to line rate probably was a better choice in 1952. The reason for CPA was to cancel phase errors in transmission and to facilitate vestigial sideband chroma channels without quadrature crosstalk. Because there was no way to electronically delay and combine alternate field or line information economically in 1952, the errors would be cancelled visually. This is very much akin to simple PAL in Europe. The field rate equivalent to "Hannover Bars" would result from transmission phase errors.
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One of the things I'm itching to figure out with this thing is if the edge effects and bars with CPA really are as bad as people make them out to be, it's one of the motivating factors to get it working as it last did. I'm hoping my brother will stop by this weekend, so we can do some digging in the color section and determine for sure what it's supposed to do. He should be able to sketch the circuit in only a couple hours, and usually takes payment in beers.
