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building a supercart from arcade shopper PCB


hloberg

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First off, I looked through the treads and couldn't find a good description on building a super cart so if there is already a thread just re-direct.

 

Now, A Super Cart is an almost most must have for the TI-99. So I decided to start a thread for those who might want to build one. It doesn't look to difficult for those with average solder skills (I hope I'm not being naive) so here I go.

So I got a super cart PCB from arcade shopper and now want to build it. I got about average soldering skills so I don't think that will be a problem and have been testing de-soldering / soldering chips or junk cartridges.

I got a E/A cartridge I plan to remove the GROM from and a got a good black shell (hate the beige).

I plan to add to the post as I build for anyone interested in building one.

 

First question, I have yet to get the other items on the build list so if anyone knows a good place for getting stuff like CMOS RAM and the such that I can't get from Radio Shack, MicroCenter or Frys please post. I am going to get what I can today from Radio Shack and will post how far I get.

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I built one recently. One thing I did to avoid head-scratching was, after desoldering and removing the AE GROM, solder a socket onto the AE cart and replace the GROM to test it still works before placing it into the Supercart.

 

If the AE cart still works, you know the GROM hasn't been damaged during desoldering and should work as required in the Supercart once the rest of the components are placed in the new board.

 

One issue I found, was my (eBay bought) CMOS RAM needed nearly 2v to retain its memory for any period. The spec said it should've been OK down to 1.5v but I suffered from data corruption after the board had been unplugged for anything over 12 hours. A new battery cured this. (The battery I originally used was "new" but had been in storage for at least 18 months.)

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got most of the parts I need.

1N914 Diodes, 1K resistors, 4.7k resistors, 1 uf Tantaium capacitor, 2 spst switches @ Radio Shack down the street. cost $12.00

2.2 uf Tantaium Capacitor, GROM chip holder, Lithium Cell and holder @ Frys. cost $ 4.00

Frys carried but didn't have in stock the 68 ohm resistor (typical of Frys).

SO,

I will need to get off the web 43256-12LP CMOS RAM and the 68 ohm resister.

Anybody got a good source where I can find the CMOS?

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I can throw a 68 Ohm resistor into an envelope and mail it to you--I have about 1,000 of them for the other cartridge boards I build, and when you only need one, the shipping most places charge bites. . .especially since one of these runs about three cents!

 

BTW, if you have a lot of old TI boards that you were mangling as test objects for desoldering practice, a lot of those have a 68 Ohm resistor on them already. . .giving you another source for that part.

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searched the forum and found the CY62256NLL was equivalent CMOS and ordered two from Mouser (thanks for the tip). Should take about a week to get here.

Now need to dig out a 68 ohm resistor from and old cart and a holder to put the CMOS into.

Edited by hloberg
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Downloaded the instructions from MainByte for the supercart that was created using an old TI cart ; helped clarify a few things (especially best position of the switches and the LED). Also found some useful software to use with the supercart.

Edited by hloberg
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I don't know if this will help you with your build at all but I've attached a photo of my completed board.

 

The switches are aligned with the edge of the board and a small drop of cyanoacrylate glue is enough to hold them in place.

 

Note the polarity on C2.

 

post-25357-0-97989900-1418645628_thumb.jpg

Edited by UKRetrogamer
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I don't know if this will help you with your build at all but I've attached a photo of my completed board.

 

The switches are aligned with the edge of the board and a small drop of cyanoacrylate glue is enough to hold them in place.

 

Note the polarity on C2.

 

attachicon.gifIMG_0003.jpg

thanks, that picture is, definitely, worth a 1000 words!
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When you're placing the switches and LED, it helps to have the lower-half of the cartridge case to hand so you can check you're not fouling the back edge of the case by sticking the switch-bodies too far back. I found the switches fit just nicely where they are pictured but you need the smallest SPST toggle switches you can source. Bigger ones may not fit. I got mine from Maplin here in the UK, so I can't provide you with any useable part nos.

 

Once fitted, I put a Sharpie mark on the lower part of the case where the center of the LED and switches fell, so I knew where to start hacking away at the case to make holes. Because the board sits almost flush with the lower cartridge case, very little (if any) case needs to be removed. Most of the plastic you'll need to cut/drill away will be removed from the top-half.

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If not part of your build-schedule, it may be worth placing a socket for the salvaged GROM, too.

Yup on that idea. don't trust my skills on re-soldering a GROM chip.

Also, thanks for the idea on how to place the switches. I got the smallest they had at Radio Shack but haven't had time to check it. We will see.

Edited by hloberg
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got my CMOS from Mouser today! Wow, was that fast, just ordered it Sunday night.

If the weather is OK (gotta solder outside on the back porch) I'll start on the construction this weekend.

 

I don't recomment soldering outside. Any breeze at all acts like a huge heat sink and sucks heat out of the iron. If the ambient temperature is low, it will of course make the problem even worse. You'll get all manner of dry joints due to the solder not being hot enough.

 

This time last year I had to graft a new section of wiring loom into my car. My plan was to solder it in place and use heat shrink to cover the joints. A nice tidy job. My iron couldn't even melt the solder - and my iron is quite a powerful unit with an external temperature controller. Even flat out the heater was on all the time - it couldn't get enough heat into the tip - it was just being leached away by the breeze. It was around 0 degrees C at the time (32F). I find that if I use the iron in the garage (where the ambient temperature is the same as outside, just without any wind/breeze) it works just fine!

 

So, if you have a shed you can use, go for that, otherwise tell the wife you're using the kitchen!

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I don't know if this will help you with your build at all but I've attached a photo of my completed board.

 

The switches are aligned with the edge of the board and a small drop of cyanoacrylate glue is enough to hold them in place.

 

Note the polarity on C2.

 

attachicon.gifIMG_0003.jpg

 

do you mind if i put this in the gallery of the cart board on my site?

 

Greg

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So, if you have a shed you can use, go for that, otherwise tell the wife you're using the kitchen!

Wife 'requested' that I take that sh move my projects to a better location than her kitchen. :grin:

Our porch is enclosed so wind isn't much of a problem and here in Dallas this time of year the temperature fluctuates between 40 to 70 degrees so I just have to hit it on the right day. Weekend might be in the 60s so maybe... otherwise I will work on it at my parents ranch over the holidays where they have a very nice shop.

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Wife 'requested' that I take that sh move my projects to a better location than her kitchen. :grin:

Our porch is enclosed so wind isn't much of a problem and here in Dallas this time of year the temperature fluctuates between 40 to 70 degrees so I just have to hit it on the right day. Weekend might be in the 60s so maybe... otherwise I will work on it at my parents ranch over the holidays where they have a very nice shop.

 

How the other half live, eh, Willsy, where they can skip across to their parent's ranch to do their soldering, rather than have to do it on cold, hard Aberdeen granite? ;-) ;-) ;-)

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How the other half live, eh, Willsy, where they can skip across to their parent's ranch to do their soldering, rather than have to do it on cold, hard Aberdeen granite? ;-) ;-) ;-)

Too bloody right mate! Reminds me of the Monty Python sketch: "We used to get up before we had gone to bed, and Father would beat us wi' a broken bottle!" :grin:

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