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That is a very interesting circuit, and while I too haven't tried it (or even checked all the resistor relations) I am sure that something like this should work fine for making a proper Component signal adaptor for the PS1.
Originally Posted by Ceph
the only thing that confused me a little at first is the use of the 4053, which is obviously not used here for its ability to select between alternate inputs for its three outputs. Instead you have grounded all the outputs and connected the input pairs together, with one such pair connected to each of the main colour inputs, just inside the coupling capacitor of each such circuit.
(For those unaware: this kind of CMOS switch is bidirectional, so the designations of outputs and inputs for the analog signals is somewhat arbitrary. This chip can be used either to select between alternate input signals, or to select between different destinations for output signals. The same chip can be used for both, just like a mechanical switch can.)
If I read the diagram correctly you would use this to short-circuit those inputs to analog ground through the analog switches of the 74HC4053 chip during the burst periods when you also also add the composite sync signal through the transistor connected to U5 via R22. This method also provides the DC bias needed for the positive inputs at pin 3 of U4, U5 and U6, while still having a very high impedance for those points outside of the burst periods, which is what lets you get away with having so small coupling capacitors, of only 100nF.
It's really quite ingenious. The only drawback I can see is that for prolonged periods of no signal (like when PS1 is off), the 74HC4053 will be continuously in 'inhibit' mode, leaving those pin 3 inputs of the op-amps 'floating' without proper DC bias. But I don't think that will be harmful.
Best regards: dlanor
I Wish i could say it was my design, i only mapped the psx pins, i found it quite by accident when looking for information to design my own RGB-YUV converter. But yeah i was also impressed, its wired in such a way that when the psx is off the wire should be off too so unless the 74HC4053 holds a charge, the chip should be non operational whenever the psx is not providing video, however i did forget one minor problem there are no audio outputs that has been corrected below. That is how i interperited the 4053 usage myself, so im sure thats exactly what it does, also you cant seem to get the RN2202 very easily so i modified it to work with a regular PNP.
Originally Posted by dlanor
Last edited by Ceph; 06-04-2010 at 02:00 PM.
Reason: Slight change in drawing