THS7374 video buffer for Supergun

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    • THS7374 video buffer for Supergun

      Hello, I bought this Supergun for cheap (23 euro) to connect jamma boards to SCART tv sets and apparently it works fine, but it doesn't buffer the video signal and it drives TTL CSYNC, so I've added a 470 ohm resistor to the CSYNC line and a buffer circuit using THS7314 (next time I'll use THS7374 with filter disabled). I like that it works with Sega 6 buttons controllers, reducing the initial cost to get this running 8o

      My setup is simple: I use the R G B pots as voltage dividers to drive the right signal directly to the THS7314. In the outputs I add a 75 ohm resistor in series for each line. I also put a ceramic 100nf capacitor in the THS7314 between Vs and GND, and also a 33uf electrolytic capacitor that removes ghosting.

      The post was edited 9 times, last by rsignal ().

    • After reading more information, I've switched to AC Coupled THS7374, buffering the Csync signal too. Since some boards give +5V and others 3.5V, along with 100nf ceramic capacitor in the input I've used a voltage divider with a 5k6 and 1k2 that gives the correct voltage in my tests.

      This is the rudimentary schematic of the experimental circuit I'm using. Instead of 330uF, the value suggested in the datasheet, I'm using 220uF caps since that's what I have on hand:



      Suggestions are welcome. This circuit is public domain.

      Update: I've replaced the 33uF capacitor with a 100uF one, as specified in the THS7374 datasheet. Next thing I'll try is to add 100nf ceramic capacitors in parallel with each output capacitor.

      Update 20/11/2018: polarity of 330uF capacitor is wrong, I think there is an error in the page 25 of the datasheet. In page 31 the output capacitors have the right polarity (negative leg towards the THS7374)

      The post was edited 6 times, last by rsignal: Update 20/11/2018: polarity of 330uF capacitor is wrong, I think there is an error in the page 25 of the datasheet. In page 31 the output capacitors have the right polarity (negative leg towards the THS7374). ().