Standards & conversion.
Pics please, if you can find it.
So, is this a one time mod or reversible?
And there is a better standard yet - 1080/30P!
I'm looking...
It was designed to switch automatically from PAL to NTSC and back, so yes, it's reversable (apart from the crystal, you'll probably need to manually replace that).
Essentially, It replaces the colour-chain with a pal re-encoding chain (as against transcoding), so if it works (and it should), you'll have no need to revert (once you go PAL, you'll never go back).
Oh yes, given that the delay-line is frequency-specific, you'll probably need to replace it with a PAL-M (That could be PAL-N) item to maintain the 90 degree phase relationship at 3.58 MHz and 15,750 Hz line rate.
Essentially, it consists of two phase invertors (2n2222 and friends) 270 ohms from c to 12v, 270 ohms from e to deck. bias at half rail. The original design didn't take DC-offset into account (it didn't seem to matter). If you're a purist, a long-tailed pair will give a better DC match, though I wouldn't bother myself with the extra complexity.
Timing, we had a PAL flipflop to inform whether the line was odd or even. You may have to roll your own. A T type toggled by HSync will probably do the trick.
A 7556 (dual timer) will probably serve for the timing chain. The first stage (triggered by the T type) switches the burst to invert. It should end just after burst time The second stage will be triggered by the first, inverting the r-y signal from the delay line.
I can't find the proto board, which sh!ts me to tears. I know the box it was in and what else was in there. There was five years of my life in that box.
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