[Coco] CoCo 2

[Rob Rosenbrock]

Brief: I’m looking for what options exist currently for connecting the CoCo to a VGA/HDMI monitor. I’ve gone through the archives somewhat, but everything I’ve seen seems to be out of stock. I want to know what I will need now, or in the future, to get my CoCo’s usable.

Background:

The 26-3136A I bought through eBay looks nice and seems to be working just fine. On this model, the RF converter lies parallel to the board rather than standing up. It has a 6847 VDG rather than the 6847T1. I haven’t broken the warranty seal yet, but I can see that the memory on this model is on a daughter card rather than being populated on the system board, and all chips appear to be soldered in place.

I have connected both it and the CoCo 3 to a Dynex 19” HDTV through the cable input and they both presented a rather poor image. Same thing if I connect the composite signal on the CoCo 3. I was able to get a half-way decent image (readable) by bringing the color down to 0.

I then tried my old Sakata composite SC-100 monitor with the CoCo 3. It’s not crystal clear, but the picture is much better and I can even read WIDTH 40. If I turn the color all the way down I see what looks like a white band on the left edge of the screen and a white border on the right side of each character - like ghosting.

That sounds familiar. On the CoCo 3, the composite output is merely a transistor buffer for the same signal that is going into the RF modulator. I’m suspecting that an aged capacitor in that circuit is screwing up alignment with the color signal. I have a recap kit on the way, so I might just replace them after all.

Either way, that CoCo 2 is not going to connect to the composite monitor without a mod. I like the idea behind the CoCoVGA - replacing the RF modulator with a composite interface without modding the case. I am interested in one if they are available somewhere. My other option is to build my own.

I’m open for options on the CoCo 3 as well. I’ve got a (hopefully) perfectly good CM-8, but it won’t last forever. All of the options I’ve seen to convert the RGB to VGA look rather convoluted involving multiple adapters to convert from one connection to another.

Sorry. I know this has been discussed before, but there’s a lot of messages to look through - and much of it seems obsolete.