GGLabs CGA2RGB – Black Screen

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    I am having trouble getting any video display using GGLabs CGA2RGB for either Commodore 128 (RGBI) or Tandy 1000HX (CGA).

    The GGLabs device is designed to convert RGBI or CGA signals to analog (15Khz) RGBS. I’m attaching the DB9 port output from the CGS2RGB to the AV3 port on the OSSC via a female to male VGA cable.

    The input is registering 15.69Khz 59.91Hz RGBHV on the OSSC and seems to be working properly.

    I can get signal on both Line2x and Line3x, (monitor registers the changes in resolution), but only black screen. Composite on both devices to CRT works fine.

    I am on firmware version .078

    Perhaps the CGA2RGB is malfunctioning?

    Has anyone tried this configuration? Any success?


    Have you verified 15khz output from the GGLabs device to another display? Admittedly finding 15khz compatible monitors isn’t easy.


    It has been a month or two since I did this, but I don’t recall doing anything special on the OSSC.
    I have this setup:

    A CGA2RGB rev B01 and a OSSC is 1.6 with firmware 0.78.

    C-128 RGBI -> CGA2RGB -> VGA OSSC -> HDMI out to a DELL 2407WFP

    I have the jumper set to pins 2-3 (closest to the board edge).
    That will set the CGA2RGB to output separate sync RGBHV.

    I direct plugged the 128 to the CGA2RGB.
    I ran a VGA cable from that to the OSSC.
    The monitor is connected to the OSSC with a HDMI cable with a DVI-D adapter on the monitor.

    From what I recall, the OSSC autosensed the RGBHV signal and worked out of the box.
    I don’t think I set Line2x or 3x.

    Is there a 5V power supply properly connected to the CGA2RGB?

    If none of that helps, let me know and I’ll set it up again and list out any other settings.


    @BuckoA51. That’s what I was thinking. I am lucky enough to have a PVM I could try. Unfortunately, I don’t currently have an appropriate DB9 VGA to BNC cable at my disposal. However, I am working on getting one for testing.

    . It sounds like I have the exact same configuration you’re using. OSSC 1.6 and CGA2RGB rev B01. I purchased a custom case for the little board and am powering it with 5v @ 2.5A. Jumper set to pins 2-3. No difference in display with power connected or disconnected however. In further tests, I did notice the little video amplifier chip (NCS2563) on the CGA2RGB heating up to an alarming degree…too hot to touch in only a few seconds. So maybe this indicates an issue with my board? In light of this, GGLabs has graciously offered to send a replacement CGA2RGB to test. I will post my results once I receive it.


    tritanium1: Did you have any luck with your new board? I’m planning to attempt a similar setup, so I want to make sure I track down the right components.

    Does anyone else know if the csync signal coming from the CGA2RGB is 75 ohm or TTL? I believe it is the former, but I’d like to be sure. Thank for your help.


    @strygo: I actually thought I posted the update…maybe it didn’t go through.

    In any event, the replacement board from GGLabs did the trick. I believe something may have affected the original in transit.

    Upon connecting the new board, 80 column mode worked right away from my C128 through the OSSC!

    This device also worked for my Tandy 1000HX producing a clear, bright picture from the CGA output.

    In regards to your second question, I would assume 75 ohm output too. Unfortunately, I can’t seem to get to the technical documents online at the moment. When I can, I’ll let you know.

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