Tandy video mod

[KenG]

OK, I decided to use one of my less than perfect motherboards as a test. It works fine, except the pins that supply sound to the monitor are broken. The ports are a real weakness on this machine. I use an adapter to get to a VGA monitor, so I use the audio port anyway. I expect this mod would take an experienced person about an hour. Took me 3 or 4! I almost put the chip in backwards. Thankfully caught that. Thought I had it done. Machine worked but no Tandy graphics and some other weird stuff. Took it back apart. One of the pins came loose while I was soldering the wires on. Fixed that. It now works! I put my Jr-IDE and backpack 3.5" drive on it. Everything seems to work OK.

Have to think about this some more. May try it on a better motherboard, may not. I did learn a few things. I used too thick of wire. Often lost other end trying to line up to solder second connection. Thinner, maybe even stranded wire should be easier to work with.

Anybody have a list of games that work with Tandy graphics on the Jr? Ultima one supports Tandy graphics but doesn't seem to pick up the mod. Is there a way to force?

[GHiero]

Try ULTIMA T

[KenG]

No go on that. Oh well. Actually the CGA graphics aren't bad.

Had better success with Pool of Radiance. Set pool.cfg for Tandy graphics and WOW! What a dirrerence. Play is real slow but the graphics are way better. Starting to think it was worth the effort.

[GHiero]

Unfortunately, it does not work and I lost the scan of the IBM PC reference card for the Ultima Trilogy, which may have indicated a command line argument to force Tandy graphics mode. Forcing Tandy with "t" does work in Ultima 4 and 5, but I believe you can only force CGA in Ultima 1 with "c"

[KenG]

Thanks for the info. I have the complete Ultima collection on CD. I may fool around with debug to see if I can figure out where and how video modes are set. If I can find that, I could force Tandy mode. I can always copy back from the CD later if I want the regular version.

[Trixter]

I use an adapter to get to a VGA monitor

You buried the lead!! What adapter do you use to convert RGB TTL to VGA?

Play is real slow but the graphics are way better.

320x200 16-color mode is twice the amount of memory to sling around, so there is a speed penalty. You may find it useful only for games not involving action.

[KenG]

I will look up the information on how I built it and post later. I found most of the information on here, but in bits and pieces. It would probably be nice to have it all in one place. I put it together and then bought a panel monitor with speakers for $25 at goodwill. It is very nice.

The games probably aren't any slower than they were on my C128 back then. I have just been spoiled.

[KenG]

Ok, the information on the RGBI to VGA converter is here: http://www.bit-c-128.com/buy

It was designed for the C128, but it works great with the Jr.

[jharre]

100_0780 (Medium).JPG

Here's a picture of the small DAC board and the larger Gonbes board.

(405.57 KiB) Not downloaded yet

It was designed for the C128, but it works great with the Jr.

Yep, it works great here, too. I had picked up a couple bare boards from J. Alex a while back http://he-insanity.blogspot.com/ and was pleased. The digital to analog board takes a handful of parts including some 1% resistors and a fairly expensive DAC chip. But, dang!, it works!!

Add the Gonbes board (lots on eBay) to convert the signal to VGA, and a PCjr to CGA pigtail and you're in business.

It also works well to convert from CGA on a 5150/5160 to VGA as well.

[KenG]

Yes, that pictue shows what I have. I bought mine, and the power supply, from the site I posted. He provides full instructions for connecting it to the Gonbes unit. I still haven't gotten around to mounting mine in a case. I have two weeks off over Vhristmas and New Years. I hope to get it done then. That would make it safer and easier to move around.

I did take me a couple of hours, on and off, to get the colors right. There are pots on the Gonbes board to adjust. I have a PCjr monitor, so I used it to compare. I have it pretty close. I think my monitor is a 17 inch. Problaby wouldn't go bigger.