Mike's PCjr Page

I figured I would post here some of my experiences getting video out of the PCjr adapted to VGA/HDMI etc.

I have my PCjr monitor and it works great but I was curious how to adapt it to other video formats. So I've found the following seem to work:

-----
C-128 RGBI DAC (http://www.bit-c128.com/)
This converts the CGA signal (digital RGB) from the PCjr to an analog RGB signal (I believe that is correct). This seems to work reasonably well, however I did notice that the colors are not quite right, there are noticeable color differences in the final output. I tried using this in conjunction with my Gonbes GBS-8220 and the Gonbes introduces some artifacts. When plugged into my OSSC there are no artifacts but the colors are still off a little. The output of this DAC is set for bare wires, so I hacked an old VGA cable in half and plugged that in, you can use bare wire to connect to the Gonbes header if desired.
-----

-----
Gonbes GBS-8220 V3.0 (eBay)
I was using this to convert the C-128 TGBI DAC analog RGB output to a test TV before I tried out an OSSC. Maybe others have had better luck, but I had quite a few ghosting artifacts using mine. They are cheap but not really all that good in my opinion. It can take the analog RGB signal output from the C-128 RGBI DAC and convert it to a standard VGA signal.
-----

-----
Open Source Scan Converter OSSC (https://videogameperfection.com/product ... converter/)
I bought one of these to use with some old video game systems and also love to see open source hardware projects. This is a frame grabber and can go from several different formats (RGB Scart, VGA, component) into HDMI (including audio) with very low latency. They also have a similar piece of hardware to convert Composite and S-Video to Component which can be fed through the OSSC to get HDMI output. This thing is great, although admittedly a little pricy. It works well with every video signal I have tossed at it and you can even send the PCjr audio output through it and into the HDMI data stream. When connected to the C-128 RGBI DAC the color discrepancies mentioned above still exist but I did not see any artifacts. When connected to the MCE2VGA, it works just fine albeit with the notes mentioned below for the MCE2VGA.
-----

-----
MCE2VGA (I got mine from https://texelec.com/product/mce2vga/)
This is a nice option for converting the digital RGBI signal of the PCjr to a VGA output, which can then be fed to a monitor directly or through the OSSC for HDMI output. The colors seemed accurate to me with this method. The only issue I saw is that you need to adjust the phase option to get the output looking clean on the board. Use the Up/Down buttons to select phase, and then left/right until it smooths out. If I had to pick, I'd say MCE2VGA to OSSC gives me the best output, or just straight MCE2VGA should be just as good if you have a VGA input on your display device.
-----

To connect either the MCE2VGA or C-128 RGBI DAC to the jr you will you need a PCjr to CGA adapter of some form (e.g. https://texelec.com/product/ibm-pcjr-cg ... out-board/, or you may be able to find the original CGA output adapter on eBay). You may also need a DB9 serial cable (with all wires installed) and some gender changers possibly. The MCE2VGA has a female DB9 connector, the C-128 RGBI DAC has a male DB9 connector on it.

Hopefully this is useful info for someone. Feel free to correct any errors I may have, it's been a while since I messed with this enough to understand the video signals with the C-128 DAC so I may not have that quite correct.

I thought I would post an update as I found another video adapter to try out! While the MCE2VGA is nice if you want VGA, it still left me wanting more due to clipping issues with trying to do video capture. Even using the vga_common_res branch from their github site didn't completely solve what I was trying to do. Although if you have a MCE2VGA and want to do video capture, I suggest you update to the vga_common_res branch.

I've been trying out a RGBtoHDMI from TexElec and this seems like a great option so far. I still need to do more testing, but so far it produces a cleaner image than MCE2VGA and I don't see any clipping issues on the sides! The output image is beautiful.

Here is a link to where I got mine from. I will say that I really like how TexElec supports the PCjr and am happy to help support them in return .
https://texelec.com/product/rgbtohdmi-ttl/

The only option for decent output is indeed the RGB2HDMI. I have two units from TexElec and they have performed flawlessly.

I should have also said that the only thing I wish it had was a way to insert audio into the HDMI audio channel. With the MCE2VGA, I was able to use a cheap VGA to HDMI converter to insert stereo audio into the HDMI signal. However, with the RGB2HDMI there is no such ability. Which means either using an HDMI audio inserter (around $50-$70 US) or using a headphone amplifier or other way to listen to the audio output from the system separate from the HDMI path.

For streaming purposes, I am looking at just connecting up separate connections for RCA left/right audio and using one channel connected to the audio output port of the PCjr and the other channel to record the beeper (via microphone or whatever).

jason wrote: ↑Wed Feb 09, 2022 4:46 pm For streaming purposes, I am looking at just connecting up separate connections for RCA left/right audio and using one channel connected to the audio output port of the PCjr and the other channel to record the beeper (via microphone or whatever).

Shameless plug that might help you explore speaker recording options: https://youtu.be/wi2tW23qb9c

As for streaming, I did something similar. Microphone and speaker into two channels on my DAC, RGB2HDMI into the capture device, mixed in OBS, canvas 4k and streaming 4k, and here's where it looked like: https://youtu.be/WCY8BtZHX-g

Trixter wrote: ↑Wed Feb 09, 2022 9:23 pm

jason wrote: ↑Wed Feb 09, 2022 4:46 pm For streaming purposes, I am looking at just connecting up separate connections for RCA left/right audio and using one channel connected to the audio output port of the PCjr and the other channel to record the beeper (via microphone or whatever).

Shameless plug that might help you explore speaker recording options: https://youtu.be/wi2tW23qb9c

As for streaming, I did something similar. Microphone and speaker into two channels on my DAC, RGB2HDMI into the capture device, mixed in OBS, canvas 4k and streaming 4k, and here's where it looked like: https://youtu.be/WCY8BtZHX-g

Nice! I'll be watching those! Thanks for sharing!

In case anyone else wants to know. I bought an HDMI audio embedder for $15 off Amazon that seems to work just great. It's actually an embedder/de-embedder but I really only need it for embedding 2 channel (or less, lol) audio. This is by far the cheapest option I see right now and apparently the unit used to be much more expensive. I'm guessing maybe it's an obsolete part and places are just trying to clear out old inventory? Who knows, but if anyone else wants to embed audio in HDMI to make life a little easier this will work.

I'm using it right now to hookup the computer to a TV I have near it so that I can easily see/hear what is going on without having to power up a headphone amplifier or anything like that.

Xantech XT-HDMI-SM-4K18G
$15.39 as of Feb 14, 2022.
https://smile.amazon.com/gp/product/B07 ... UTF8&psc=1

Snagged one, thanks for the link! Yes, this is easier than running a cable to my DAC. Of course, it remains to be seen if this audio embedder can deal with odd resolutions and rates (my RGB2HDMI currently outputs CGA including overscan to a 1600x1200 target) but we'll see.

Trixter wrote: ↑Tue Feb 15, 2022 10:10 am Snagged one, thanks for the link! Yes, this is easier than running a cable to my DAC. Of course, it remains to be seen if this audio embedder can deal with odd resolutions and rates (my RGB2HDMI currently outputs CGA including overscan to a 1600x1200 target) but we'll see.

I think you can set it up so that the unit doesn't do the handshaking and connects using the resolution of the output monitor and not the embedder itself. So, I want to say it should work if it works now. You just have to set Dip switch 3 to the down position = Hot Plug Detect On. That should keep the unit from interfering with the resolution detection..I think. There is also a "software control EDID" setting but I'm not 100% sure what that does.

So far, I just have it set to 1080p output to a TV/monitor which has so far worked for my video capture card and TV that I've connected it to.

What settings are you using on the RGB2HDMI? Do you have any recommendations? I haven't really had much time to try different settings out on mine yet. Maybe a good idea for a video if you haven't made one already?

Definitely future video, but not until after April or so as I'm working on a project until then. But definitely video material, since I've struggled with this for decades until the RGB2HDMI came along.