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Hans23

Can anyone identify this internal 32k RAM extension board?

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Hi,

 

I received a console for repair and it has this 32k RAM expansion built in:

 

PXL_20210829_094221757.thumb.jpg.ef1b11729cb74811440056a012736240.jpg

 

It has a (leaked) NiCd buffer battery connected to the two "ACCU" pins on the upper right corner.  The IDC connector goes to the console like this:

 

PXL_20210829_094303703.thumb.jpg.7f64dd9ec78f7ee00e62f5a0eeb26cdb.jpg

 

I hope that the CPU is not dead, as that'd be quite an ordeal to move over.  In any case, some info on the RAM board would be useful, in particular as I would like to know whether any traces on the motherboard were cut for the installation.  I have certainly looked for such modifications, but the cables don't exactly make things easy :D

 

Thanks,

Hans

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Never seen the board, but maybe this helps.

 @Tursi / harmlesslion

 

Also in the Dutch TIjdingen magazine in 80's are instructions how to built 32K in the console. With help of the "Regio Zeeland" team i got my first 32K and then load assembly games via cassette player. (See my channel Youtube TI99VIDEOS for more details).

 

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That one looks like the board Jürgen Stelter from the TI Workshop Wiesbaden designed. I think it originally came with a page or two of instructions.

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There's no need to cut traces unless you are changing the operation of the multiplexer, so as long as it's not an accelerated 16-bit RAM mod, it should be fine.

 

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I did find a cut trace on the board now, but I have not yet figured out what connection is broken by it.  The console works - without the RAM extension connected - when I reconnect the cut trace.  The board does not look very complex and if I can´t find any documentation, it might be possible to figure it out.  The large number of connections that are made to the motherboard make that a project that I´d not want to immediately jump onto :)

 

-Hans

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I'm not offering (yet), but if you post high res pics of both sides of the PCB, maybe someone can make an educated guess to get us 80% of the way there ;)

 

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I only was able to find this pictures, but it´s a 32K PEB-card from Jürgen Stelter, not the inside mod.

 

 

 

32KB-RAM-Stelter-02.thumb.jpg.830620da9176b908b62dde879a5c385d.jpg32KB-RAM-Stelter-01.thumb.jpg.c768a6159fb88ca939c7542a3c66d2c7.jpg

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The

10 minutes ago, Schmitzi said:

I only was able to find this pictures, but it´s a 32K PEB-card from Jürgen Stelter, not the inside mod.

The card on the pictures is a PEB card, but the description is for the internal board that I am faced with :)  Most of the important information is on the first page, but if anyone happens to have the second page, I'd be interested.  Thank you!

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Posted (edited)

For those who don't read German:  This internal 32k card uses the 16 bit data bus and it attaches directly to the CPU.  There is additional logic on the board to provide wait states to make it work better with the TMS9929A VDP.  I tested it without wait states and a F18A installed and it works fine, although I did not immediately have an idea how to measure the speed difference.  Here is a full set of pictures:

 

PXL_20210830_070546703.thumb.jpg.b8613fafb3bee3b7cb96c6d88f76a289.jpg

 

PXL_20210830_070435302.thumb.jpg.337707f5653ec4cf95d9c12afff36581.jpg

 

PXL_20210830_070411156.thumb.jpg.aa26cb0d2029a061f6b5fa3912ed8a3d.jpg

 

P.S.: I like the crusty 74LS03 which is older than the TI-99/4A itself :)

Edited by Hans23
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I just had a look for my old TI console which was equipped with the internal 32K RAM expansion. I cannot remember, though, who installed that expansion. At that time I was about 17 years old, I was able to solder things, but I don't remember whether I was responsible for this cable mess. It was not my father, I am quite sure, because we went separate ways concerning computing in those days.

 

As you can see, there are two buttons (yellow = LOAD, red = RESET) and a flip switch, supposedly for turning on the wait states.

Int32k.jpg

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