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rkrenicki

TI99/4A Motherboard Replacement (In Progress)

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Posted (edited)
1 hour ago, rkrenicki said:

So, just to be 100% clear:   You are using a TIM9904/74LS362 with a 48MHz Crystal, 3.3uH Inductor and a 22pF capacitor, and that works for you?

 

I am trying to find a datasheet for the non-A version of the TIM9904, but I have not yet found one...

I have to find my notes for having all precisions of any values (it was in 2018) and I will back to you.

You can donwload another TIM9904 documentation on my website,  here: http://www.ti99.com/ti/data/documents/TIM9904.pdf

Edited by fabrice montupet
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Posted (edited)
12 hours ago, fabrice montupet said:

:lol:

I didn't made the connection with this (great) movie because some replicas have been differently translated in French!  The "Flux Capacitor" as been replaced by "Convecteur temporel" ("Time Convertor" en English).

 

Ah, you have a similar problem like we have in German! 🙂

 

This was a particularly weird thing in the German version. The "flux capacitor" was originally translated as "Fluxkondensator" (Kondensator is the correct electrical term for capacitor). However, the dubbing staff or the actors, don't know, misunderstood it and took "Fluxkompensator" which is now the term known from the movie. It does not really matter whether you compensate the flux or have a capacitance to charge ... as long as the Libyans don't find you.

 

Edit: At least that's what people say. Come to think of it, it may have even be done on purpose to improve lip syncing. "Kompensator" is closer to "capacitor" than "Kondensator"; the "nd" does not sync well with the "p", but the "mp" does. And about the technical term, who cares. They are doing an awful lot of effort to get things into sync, maybe this is why dubbing is called "Synchronisation" in German.

Edited by mizapf
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Posted (edited)

Alright, I think I can safely rule out a clock problem.   Both with a new 0.33uH inductor and the old-stock inductor, I get a solid 2.99964MHz clock on 4 phases, both normal and inverted.   I tried one of my other TIM9904's and also got the same clock exactly.

 

Phi-0

20210403_170612674_iOS.thumb.jpg.04b58a3aab64a3605e692c96d85b6987.jpg

 

/Phi-1

20210403_171439870_iOS.thumb.jpg.59a81d2c34419a60e1de47bc4251567e.jpg

 

 

I am going to socket the RAM and ROM on my QI console sometime this weekend, to that I can test those chips.   They are still big question marks to me right now.

Edited by rkrenicki
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Have you checked for activity on the ROM and RAM chip select pins?

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Posted (edited)
58 minutes ago, Stuart said:

Have you checked for activity on the ROM and RAM chip select pins?

Yes, /ROMEN, /MB, and /WR all have normal looking waveforms.   

 

I went through and probed the rest of the lines, and it seems that Non-buffered A3 and A4 may have an issue as they are staying mostly low.  I started pulling chips one at a time until I saw normal strobing on those lines, and it looks like the U610 ROM may be the issue here.

Edited by rkrenicki
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Here's some ideas/pipe dreams from me for perhaps the enhanced version: :D

 

- As already mentioned, a reset button, internal 32k, speech synth, parallel port, VGA, etc. 

 

- Built in SD card interface, perhaps positioned so it can come out of the cartridge slot using a 3D printed filler plate/SD slot, which could also hold the reset button in a recessed spot to keep it from being pressed accidentally. Seems to me somebody has already designed an SD side car that's open source which you might be able to incorporate. If you need help with that I can design the filler plate and other 3D printed parts.

 

Ability to mount a TIPI internally.

 

- Ditch the cassette port and pipe the VGA out through that spot since it's the right shape for that connector, if need be put in a mini-jack for cassette that uses the hole left from the original video out.  

 

- Simplified power input to maybe just 24 or 12 volts, that way we're not dependent on the original large wall-wart and can use common off-the-shelf replacements. Again maybe you could get rid of the cassette port altogether or at least leave an unpopulated spot for a jack if someone really wants it, put the power input with the original video out was, put a VGA port where the cassette port was then use the spot where the original power supply plugged in for other things such as the network jack for the TIPI.  

 

- EPROM for several permanent, built in ROMs for things people are always using like X-basic, Editor/Assembler, etc.   

 

- Soft power-on like modern PC power supplies. Not really that important, but it would get rid of the "bonk" when the power slams on with the normal switch and might be kinder to the hardware over the long term. 

 

- Ability to switch to an overclock mode. I don't know how practical that is for this chipset and overall design, but it would be cool to be able to kick it into turbo for particularly slow stuff, rather like you could with older PCs like a 486. 

 

- Built in ability to use a USB keyboard. That also might give one the ability to remove the original keyboard, put a 3D printed or CNC'd filler plate over it and use the space for other hardware? Or if you want to stick with the original keyboard make it so it can be mounted in a separate case and connected remotely either through simpler wiring or even a wireless connection.

 

- Maybe a smaller, more reliable connector in the expansion port that perhaps has more abilities than the original and would be easier to get female connectors for. It would rule out using an original PEB (unless an adapter can be made... replacement PEB interface card that doesn't need the "fire hose?"), but people could design newer, better things to replace it with. 

Edited by Tornadoboy
I'm an illiterate bastard :p

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On 4/3/2021 at 4:02 AM, mizapf said:

Edit: At least that's what people say. Come to think of it, it may have even be done on purpose to improve lip syncing. "Kompensator" is closer to "capacitor" than "Kondensator"; the "nd" does not sync well with the "p", but the "mp" does. And about the technical term, who cares. They are doing an awful lot of effort to get things into sync, maybe this is why dubbing is called "Synchronisation" in German.

That's kind of fascinating, actually! I didn't know either the French or German terms before :)

 

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I just received another Non-QI TI99 in the mail.  It is pretty beat up, but it does function.   I have not had a chance to open it up and socket the ROMs yet.

 

I may actually go though and socket everything and use this as a testing reference while I am at it.

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