powers@uklirb.informatik.uni-kl.de (David Powers ) (01/21/91)
I am currently on an extended contract in Europe (coming from Australia), and have recently being feeling lost without my hulking great 386. As I wanted portability (but have also already a pocket computer) and a big extended keyboard, I wnet for an Amstrad PPC512. But the display is terrible. So I thought, buy some plugs and do an RGB connection to the TV. Problem 1. The Euro-connector "documentation" has a "blanking" input (no further explanation), The PC "documents" outputs including HSYNC and VSYNC (again no further explanation). Problem 2. Whilst the line frequency is only about 1% different, the 625 vs 525 lines may be a problem (in Australia I used a multinorm Sony Profile, here an ordinary Loewe) Problem 3. The Loewe has no sync polarity switch. So I tried straight composite/monochrom video, calculated the new values for the CRTC registers to adjust the frame frequency, and... There was too much tearing for it to stabilize. So I tried the RGB, "blanking" with both HSYNC and VSYNC and combined - it didn't produce more than some faint fuzziness of different kinds. So I tried the RGB, "blanking" with the monochrome signal. That was enough to stablize vertically for carefully selected values (slightly different from best for composite video, both beyond the calculated values). Here I noticed it was most table with the text in the sync position, suggesting that the sense of "blanking" was inverted. So I tried the RGB with sync from the tuned TV station. The optimal response here corresponded with the calculated values, with a slope on verticals (corresponding to the difference in horizontal frequencies?) which varied slightly according to station (as might be expected). So I am now left feeling positive that the problem is that I can't obtain the "blanking" signal required by the Euro-Connector. Can anyone support this supposition? Can anyone provide more technical details? Suggest and invertion/combination circuit to synthesize the required "blanking"? Suggest where I might find an inverted signal input somewhere in the Loewe M21 + Videotext? (That is preferable to some additional inversion box - there is actually a cut out on the case for an sync polarity switch, but I don't know what option brings that, and don't what BTX just for that reason!) Any help or comments appreciated, especially on the two signal and socket standards. Cheers, David Powers