Will OSSC work for 1989 Super Offroad Arcade conversion to LCD?

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  • #22571
    protraxduner
    Participant

    Will OSSC work for 1989 Super Offroad Arcade conversion to LCD? Game works perfect feeding original TUBE. I have unsuccessfully tried using the gbs8220 converter, not working. I have used the gbs8220 on other older arcades successfully. The arcade output is RGB, ground, Hsync, Vsync. That is my limit of knowledge. Upon further analysis through another arcade forum i was advised to reduce the voltage of the Hysnc and Vsync from ~4.5V to around ~3V which i did but still didnt help. I then bought a chip to combine the Hsync and Vsync to combined Sync and that also did not work. Can someone tell me if OSSC will work for me or how i can tell or just any advise? thanks

    #22572
    nmalinoski
    Participant

    This is one of the use cases the OSSC was designed to address (maybe not arcade-specific, but digitizing and line-doubling analog video for use on modern displays).

    AV3 on the OSSC will take the RGBHV with TTL-level sync just fine; but make sure to not run amplified audio into the OSSC, you may damage it. (I assume that won’t be a problem if you’re just trying to adapt the video.)

    It should work, but there is a chance your monitor won’t like the framerate from the game; I’m not sure there’s a way to tell without actually trying.

    #22574
    protraxduner
    Participant

    Again I am very new to this so I really don’t want to spend $200 to test something. There is NO audio in this conversion so that should be fine. Can you expand on what you mean by my monitor may not like the frame rate? If it matters I am using a relatively inexpensive 40″ TV for this retromodded arcade. I have done this on another game and it turned out great. This game itself is pretty minimal graphics quality so all i am asking for is something that present a decent picture, doesnt even have to be great or better than original. thanks

    #22576
    nmalinoski
    Participant

    I don’t have much experience with arcade hardware; but, from the console side of things, I know there are a number of televisions that don’t like Line 3x/4x/5x from the OSSC, either because of the resulting resolution (Not too many TVs like 960p, for example), or because the refresh rate isn’t exactly 59.94Hz or 60Hz. In the cases of the NES and SNES, some frames are cut short by one line, which results in a jittery sync that some flat-panel televisions can’t lock onto because it’s not an exact, consistent cadence. CRTs don’t care about any of that.

    In my experience, I’ve had no trouble with an Xbox, PS2, PlayStation (both original and PSone), N64 (through S-Video and an RGB decoder), NES (through composite and the same RGB decoder), nor a Dreamcast on my 32-inch Samsung LCD (LN32B360somethingorother from about 2009) using just Line2x on 240p and 480i content, and Passthrough for 480p and up, but I did not have luck with Line3x, 4x, or 5x for 240p content, nor Line2x for 480p content. I’m not sure if those modes generate a slightly nonstandard refresh rate, or if my TV just doesn’t like the resulting resolutions, or both.

    #22577
    BuckoA51
    Keymaster

    According to MAME, Iron Man runs at 60hz dead on, so that should work on any modern TV.

    #22578
    protraxduner
    Participant

    SO i literally have 6 wires (no connector this is how the video arcade game comes hard wired to CRT). How do i get my R G B, ground, Hsync, Vsync into this converter? Mention of AV3 input but that is VGA connector which i don’t have.

    #22583
    BuckoA51
    Keymaster

    That’s something probably best asked on the arcade forums. I’d recommend combining h and v sync into csync and building an interface to AV1/SCART, but you will need to check the voltages and sync levels to make sure it’s 75 ohm.

    #22584
    protraxduner
    Participant

    Sorry for all the questions but:
    1. what/how do i go about combining h and v sync. I have done this with 74LS32 chip is that correct?
    2. what are acceptable voltage levels for syncs?
    3. how do i know if its 75 ohm?

    #22590
    paulb_nl
    Participant

    1. I do believe simply using an OR gate will not provide proper sync but someone more knowledgeable would have to confirm that. It might be easier to just buy a VGA connector so you can connect everything to AV3 without having to combine sync and reduce TTL levels for SCART.

    2. Here are some video level voltages: https://www.maximintegrated.com/en/app-notes/index.mvp/id/1184 The RGB voltages when 75 Ohm terminated should max be at 0.7V pp and sync around 0.3V pp. 75 Ohm terminated means that the wire is connected to the display/OSSC which have 75 Ohm resistors terminating to ground inside.

    3. With 75 Ohm he means it should be the above video level voltages and not TTL.

    #22593
    Mightysquirrel
    Participant

    This is known to work with the OSSC, as per several streamers on Twitch.

    Maybe get the video to sync, and solder/split off the voltages from the power supply into the adapter, and then use the SCART connector? This should also do audio.

    #22702
    protraxduner
    Participant

    Still looking for more reassurance that this will work for what i have?

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