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zxMarce

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About zxMarce

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  1. For the ones after it, this is the same KiCAD 5 schematic (corrected an omission of two caps' references and values), but including the italian-like video out modification. Hope it serves someone. Regards, zxMarce. Modulator N-PAL - Video Out.sch
  2. Here are some pics I took today of my modded N-PAL modulator, PHA-2031. The last pic is the image as I see it on a 32" Philips TV via A/V Input. Sometimes better, sometimes worse. The modification I made -I realized later- is one from the TI99IUC. Only changes I made was to replace the 68 Ohm resistor with a 75 Ohm one by connecting two 150 Ohm resistors in parallel (did not have any 68 Ohm at hand), and I used a SS9018 transistor (from a disassembled Timex/Sinclair 1000 RF modulator) instead of a BC547. I also connected my transistor between LM1889N's pins 13 and 14, given that pins 14 and 16 are both positive supplies. I suspect something in my chroma subcircuit is dodgy because whenever I touch some component leads (mostly anything on LM1889N's pin 15, audio subcarrier input) I can make the circuit output color (noisy of course, but color), while lately I mostly get noise-free B/W. Maybe my 3.582056MHz crystal' s gone; I played a bit with its tuning trimmer without result. For the eagle-eyed viewing my pictures, I also changed the non-shielded cable to shielded in the video mod; this I did after taking the photos. Hope this helps someone; as I said, I'll do a second schematic with the modifications. The modulator front: The back: The side with the A/V RCAs: The guts: Detail of the TV/Computer switching relay: The horrible mess - I added the multi way connector to be able to separate the board from the input cable (and forgot to include my own outputs - oh well): Detail of the multi way connector: Detail of the video modification: Same, but from the other side: The... er... "picture" I get from my TV: Regards, zxMarce.
  3. Well... Got most of the original circuit for the PHA-2031 N-PAL modulator on a KiCAD 5 schematic. Attached. The circuit does not include the LM1889's RF parts (for the TV channels), as I only wanted to get composite out of the device. Basically, these RF parts are a L-C tank for the desired TV channel and that's pretty much it. Maybe an extra decoupling cap. I'll make a second schematic with my modifications. Regards, zxMarce Modulator N-PAL Schematic (KiCAD 5).7z
  4. Hi there, I just signed up for some TI goodness. A brief history, off the top of my head - Actual facts may slightly differ. The first home computer I saw was a TI-99/4A with its PEB at a computer dealer in the early '80s. It was being used by a young person, and before my eyes a Parsec-style game slowly started to appear - the person was coding the game right there, live! At the time, Texas Instruments did have some HQs here in Argentina (guess it still does); they not only had representation but they actually did manufacture transistors here (sadly, this is no more so). It appears that "our" TIs had a national modulator (PHA-2031) designed and manufactured locally for our own PAL-N systems (50Hz vertical, 15.625kHz horizontal, 3.582056MHz chroma burst, 4.5MHz audio subcarrier). Not the same as the European (PAL-B, as we know them here) ones. Googled hi and lo, but could not get a schematic of it, so I got my hands dirty. I have a very rough and somewhat incomplete schematic of the beast (pencil!). I did not get to the RF part, basically because I just wanted to get to the A/V signal, and the RF part is just an L-C tank for the LM1889N it uses plus some support passives. I did get some A/V out of the modulator, albeit video is slightly noisy (maybe a cap or two need replacing, be it in the modulator and/or the TI power supply itself). I have the modulator board scan, a Pinta project with board's track and pad layers (flipped, so I could just pencil-draw over it the components by copying their positions from the board), and the handmade -partial- schematic of the modulator. I did not make a second schematic with my modifications yet; I will do it and upload the whole bunch later to this thread. My hopes are that someone sees what I did and yells me something along the lines of "Hey, if you get video this way [.....] it will be clean" or even "change caps Cxx, Cyy [...] and video will work". Regards, zxMarce.
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