111 replies to this topic

[Jess Ragan]

Yeah, the TI99/4A was the preferred computer in Michigan elementary schools. I remember being utterly engrossed by the Scott-Foresman educational titles, which all had the look and feel of top-quality arcade games. Sadly, the TI99/4As didn't stick around forever, and neither did I... when I moved to a new school, there was a single, lonely Apple IIe waiting for me there.

[Tempest]

Jess Ragan, on Tue Sep 11, 2007 8:50 PM, said:

Yeah, the TI99/4A was the preferred computer in Michigan elementary schools.

Really? I remember having Commodore PET computers at my school. Then they got two Apple II+'s and I was in heaven.

Tempest

[missyrelm]

djpubba, on Fri Sep 7, 2007 6:20 PM, said:

I've got a nice desoldering iron. Let's see who get's this done first.

This interest in modding the TI-99/4A is really good to see!

I grew up with the TI-99/4A. I learned BASIC on one when I was in 4th or 5th grade, and I'd write all these programs and save them on the cassette tape recorder, including one as a school science fair project. I think for Halloween or something I dressed up as a TI-99/4A keyboard! (LOL, guess I was a TI fanboy!)
The games were a lot of fun, esp. I remember Chisholm Trail, Ti Invaders, Car Wars, and Hunt The Wumpus. Then there was the speech synthesizer, which was unlike anything else out there at the time. There was this "operation on a patient" game that used it, but I can't remember the name. I wrote a lot of music on it too, there's really nothing like some of the sounds it made, esp. with the speech synthesizer.

Up until 1999 when I lost it in a move, I used an adaptor to connect to a coaxial TV, and would play the games out of nostalgia.

Didn't want to put this in marketplace because no one has accomplished it yet, but just to let people know that there is interest in this, if someone does accomplish component video/S-video output from a TI-99/4A, I'd be very interested in buying it. And while I don't really know anything about electronics, I'd be very happy to help people trying to attempt this with finding parts and stuff. I think there is already a mod out there that that will allow it to be played with Atari Joysticks. That and a clear picture would be very cool, and hopefully revive interest in this very unique and often ignored system.

[djpubba]

I got a cable to use Atari sticks from eBay.

I got my Gorf RGB interface board. Still waiting for the 9928 to arrive from Arcadechips.com and then I can start tinkering.

I won't sell mod kits but I'll post my results and how I did it if I succeed.

[Artlover]

djpubba, on Sat Sep 8, 2007 11:37 AM, said:

A heat gun is the most efficent and easy method and is how professional parts-salvage companies do it (directed hot air flow, specifically).

I've been hesitant to reply, but I can't control myself anymore.

Professional focused HAF desoldering stations (Weller makes some nice ones) and home depot heat guns are not even remotely simmlar beyond both having hot air invovled. Controlled focus of hot air, percise temp control at required melting point temps, etc..

I've read the tutorials on using a heat gun for chip removal. Talking about using one of those narrow fan tips holding it over the row of pins, being patient because it can take several minutes. Several minutes? That goes against every thermal protection consideration that exists for IC's. Same for the oven. Chips can be toasted in just a few seconds. Sure, it will remove chips well enough, but will they still be functional. I guess it depends on the chips. Some may take the abuse better then others. But some chips are thermaly sensitive enough that desoldering a few consecutive pins in a row instead of a staggered pattern is enough to kill them.

From all the tutorials I've read on the internet, the heatgun seems to be a rather popular way to go, which absolutly flabergasts me, that so many people think nothing of long standing soldering/desoldering techniques that exist for a reason and that apparently a lot of IC's out there can actually withstand the thermal abuse.

I digress. You guys do it however you want. Personaly, I'll continue doing it the right way.

[djpubba]

I believe you. However, we're not talking about precious commodities here. We're talking about trying to save $10 by using something you already have laying around, that may or may not already be dead anyway, but is destined for the scrap heap in the end one way or another.

More info for the do-it-yourselfer on a budget:

http://web.archive.org/web/20060519130120/...move/index.html

[Jess Ragan]

I bought a chip removal tool on eBay, but I'm not entirely sure how to use it. They're just a bunch of metal rods with thin wires attached to them... I guess you're supposed to lay the wire down on the legs of the chip, then heat it up until the solder melts. Then you're supposed to pull the chip out with your third hand... oh wait, I don't have one of those!

[missyrelm]

Perhaps this was obvious but I have read that there are four links
that would need to be changed to feed the three
components to the rear connector and to bypass the composite video
circuitry on the board.

I think there were some third party attempts to try this in the 90's. I've heard talk of something called the Video Turtle that supposedly outputted S-Video from the TI but all I could find *anywhere* online is a mention in the TI-99 Home Computer Encyclopedia that only says that it was made by TexComp and released MAY 1997.
Doesn't seem likely to be able to get ahold of that. Also I'm
unclear as to exactly how it got S-video out of the TI's 9918A
composite output.

Also there was the Tiny Tim which seems even more dicey and probably just as difficult to obtain.

On the other hand, Arcade Chips sells the 9928 for $10

djpubba, on Fri Sep 7, 2007 6:20 PM, said:

I found a place that sells just the chip alone.

http://www.arcadechi...?products_id=85

I've got a nice desoldering iron. Let's see who get's this done first.

[Longhorn Engineer]

Hmm been looking at this for the past couple days.

Seems the only way possible is to install the 9928 to get R-Y, B-Y, and Y. To go from that to S-Video you need a converter. I have seen plenty of RGB->S-Video but zero Component -> S-Video but there are a few Component -> RGB schematics out there. So you would need two conversions, Component -> RGB -> S-Video. I would assume you would pick up some noise and the like from all the converting. But if you are looking for Component then you should be fine.

Tho I don't know a whole lot about video signals and all. I will ask some of my double E buddies and see what they say.

[djpubba]

I just got notice last night that Arcade Chips shipped my chip. They had a backlog of orders, I guess.

I'm skipping s-video and going for RGB.

[Longhorn Engineer]

Well if you can get RGB then S-Video is possible as well.

[djpubba]

Still nothing from ArcadeChips.com. I'm starting to wish I had found another source for the chip.

[missyrelm]

I hope that you get it soon, or if it got lost in the mail, they resend. Bad news for those of us interested in replicating this project if it works.

I've posted about this project on the TI-99/4a Yahoo group and I know I'm not the only one who would really like to see someone do this successfully so they can have it done or do it themselves.
There's at least one person there who is also planning on trying this soon.

I've been looking around the web for another source of new 9928's and so far haven't found one so I'm crossing my fingers that ArcadeChips comes though and it doesn't have to be taken out of another machine.

djpubba, on Tue Sep 25, 2007 5:12 PM, said:

Still nothing from ArcadeChips.com. I'm starting to wish I had found another source for the chip.

[djpubba]

There's a big thread on rec.games.video.arcade.collecting about ArcadeChips.com having 200 shipments stolen from the post office. He emailed me again yesterday saying I'd have it by Thursday, so fingers crossed for weekend tinkering.

[Jess Ragan]

I can tell you right now that desoldering chips and other components from a ColecoVision is a SUPREME pain in the ass. The pins are bent and they're covered in some weird super-solder that's hard to melt and vacuum away. I haven't been able to remove ANYTHING except a joystick port, which I promptly moved to another system in need of one. So trying to transport a TMS9918 to a ColecoVision has been a bust. I was hoping this would work because the graphics chip was borked in the ColecoVision I bought on eBay, and my old CV motherboard is covered in rust and in sorry shape. Oh well, you can't always get what you want!

[JamesD]

Check MSX websites for info on the video output. They seem to mod their systems a lot more than Ti people.

[Tursi]

Quote

So trying to transport a TMS9918 to a ColecoVision has been a bust. I was hoping this would work because the graphics chip was borked in the ColecoVision I bought on eBay

If it's borked anyway, why not just cut the old chip out and solder the 9918 on top? It's hacky but usually works.

(Not familiar with the CV board layout.. I should get one.)

(added: might be able to use this technique: http://www.harmlessl...gallery/cartrec )

Edited by Tursi, Thu Sep 27, 2007 11:36 AM.

[djpubba]

My ArcadeChips.com order *finally* arrived today and they included a free extra 9928! woot. Weekend tinkering for sure.

[Jess Ragan]

Tursi, on Thu Sep 27, 2007 5:35 PM, said:

Quote

So trying to transport a TMS9918 to a ColecoVision has been a bust. I was hoping this would work because the graphics chip was borked in the ColecoVision I bought on eBay

If it's borked anyway, why not just cut the old chip out and solder the 9918 on top? It's hacky but usually works.

(Not familiar with the CV board layout.. I should get one.)

(added: might be able to use this technique: http://www.harmlessl...gallery/cartrec )

Hmm... that's an interesting idea! I might have to give this a try, just for fun...

[djpubba]

Mwahahaha.

I did a quick test with test clips to see if it'd work. Oh yes. It does. Woooo.

The lines in the screen are just because of the camera. The colors are *slightly* washed out. This could be my monitor. I'll try it on another later.

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[Longhorn Engineer]

djpubba, on Sat Sep 29, 2007 12:22 AM, said:

Mwahahaha.

I did a quick test with test clips to see if it'd work. Oh yes. It does. Woooo.

The lines in the screen are just because of the camera. The colors are *slightly* washed out. This could be my monitor. I'll try it on another later.

nice

[Tursi]

hehehe.. beautiful! That's really nice to see!

[missyrelm]

If anyone is willing to replicate this process for me, please PM.
I'm in the process of buying a TI-99/4A console right now, I could save a lot of money by shipping it directly to the person willing to do it. My goal would probably be S-video. (My TV accepts component inputs, but I'm not sure if these would work or not or if S-Video would look better).

Tursi, on Sat Sep 29, 2007 1:26 AM, said:

hehehe.. beautiful! That's really nice to see!

[djpubba]

It turns out the circuit from Gorf isn't quite ideal so I've got a bit of tinkering to do before this is ready to document. For one, the Gorf board is designed to take R-Y, B-Y and composite video while the 9928 supplies R-Y, B-Y and Y. I was still able to easily get a picture because the monitor I was using is a multi-sync which supports sync-on-green. So I jumpered Y over to the Green wire and it synced right up. It made the colors wonky however. This is why they looked a little washed out to me.

The good news is that I did a little research and found that the "Vidiot" board in a Baby Pac-man (pinball/video game hybrid) uses a 9928 and converts its output to standard RGB + Sync. Schematics are available for the Vidiot and it's a pretty easy circuit which runs on +12vdc (regulated to +8.2vdc for the amps). However, instead of building the circuit from scratch, I found a parts Vidiot on eBay for $12.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...em=130156225686

When it gets here, I'll see how easy it'd be to cut the section I need out of the board and cram it inside the TI.

Edited by djpubba, Sun Oct 7, 2007 11:08 PM.

[Tursi]

Great stuff, DJPubba! I'll be interested in hearing how that turns out, and this is definately something I want to try too.