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Timex Sinclair 2068- ZX Spectrum compatibility cartridge?


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#1 Tupin OFFLINE  

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Posted Thu Jul 10, 2014 11:04 PM

So I managed to pick one of these what are essentially NTSC ZX Spectrums up for a decent price, and I would obviously like to see it running a considerable library of ZX Spectrum games. I know that the cartridge was originally released when it first came out, but I seem to have found one online now:

 

http://yarek.com/basket/?h=umcb

 

Anyone out there know if he's still doing this? Or anyone else have a Timex Sinclair 2068?



#2 R.Cade OFFLINE  

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Posted Mon Mar 16, 2015 7:37 PM

Hi Tupin,

 

Sorry for the late reply.  I just picked up one of these myself.  I simply burned an EPROM from the TC2048 and inserted into the main ROM socket, and it seems to be completely compatible with the Spectrum 48k. 

 

The only thing odd is the colors are not exact... i.e. some things that should have black backgrounds do not. I think this is the difference between the ULA in the Spectrum vs. the Timex, as the Timex is a newer version and has new video modes. You can see this problem in Youtube videos as well...


Edited by R.Cade, Mon Mar 16, 2015 7:40 PM.


#3 remowilliams OFFLINE  

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Posted Mon Mar 16, 2015 7:41 PM

Any chance you can post that ROM file or a link?  I'd really like to do the same if that works.  :)



#4 R.Cade OFFLINE  

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Posted Tue Mar 17, 2015 6:22 AM

Sure... It's on this page.

 

http://www.shadowmag...ctrum/roms.html

 

The 2048 ROM is essentially exactly the same as the Spectrum except it sends an extra command to initialize the newer video properly. I left the other extra 8k Timex ROM in mine, but it's not used by the 2048 ROM.  I loaded many Spectrum games and they all played fine.

 

It's strange - everything I found online said you have to mod the board to use EPROM, but I didn't... Mine just worked with straight swap. The documents all mention bridging pin 1 to 28, but that doesn't even make sense- pin 1 is programming voltage and isn't needed in normal use. You can use a 27256 and burn the original 16k TS2068 ROM along with the TC2048 ROM if you wanted, pull pin 27 up and put a 0v/5v switch on it to toggle. I didn't bother, because there is next to no programs available for the regular TS2068.   :)

 

The only problem I have with mine is it didn't come with a power supply. I've tried a few wall-warts, and they work, but all cause various video interference issues. Perhaps the original one was better or filtered more than the junk ones in my "box of wires".


Edited by R.Cade, Tue Mar 17, 2015 6:48 AM.


#5 remowilliams OFFLINE  

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Posted Fri Mar 20, 2015 9:59 AM

 

It's strange - everything I found online said you have to mod the board to use EPROM, but I didn't... Mine just worked with straight swap.

 

You replaced U16 with a 27128?  I just tried it in mine, doesn't seem to work.



#6 R.Cade OFFLINE  

R.Cade

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Posted Fri Mar 20, 2015 10:51 AM

27256, but the pinout is almost the same. Pin 27 is /PGM on a 27128 instead of A14, so you might have to tie it to 5V. If it's grounded the chip will be disabled. Try jumping it to pin 28 (short them together).



#7 remowilliams OFFLINE  

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Posted Fri Mar 20, 2015 11:06 AM

Ah yes that makes sense.  I just switched to a 27256 and dropped it in, success!

 

Boy does this unit have some heinous video noise though, the DVE wart here is (as far as I know) the original.  

 

Do you by chance hear buzzing from a coil in the upper left of the board near the RF section?



#8 R.Cade OFFLINE  

R.Cade

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Posted Fri Mar 20, 2015 11:21 AM

Yes, mine buzzes and has bad interference, too.  I think it must just be "normal"...  It's actually good to hear it's not my power supply, and the original does that too.

 

It's hard to tell if it's a coil buzzing or just high-frequency noise coming out of the little speaker.  Probably both.



#9 Centurion OFFLINE  

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Posted Sat Mar 28, 2015 10:21 PM

Wow, cool!

#10 factus10 OFFLINE  

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Posted Fri Apr 3, 2015 11:10 AM

I'm a little late to the game but there's also the option of a twister board with a Spectrum rom built in. It actually comes with both Spectrum and SE Basic roms (it uses a 27256).

 

Here's the auction for one I purchased:

http://www.ebay.com/itm/121605523078

 

Contact the seller and he'll put up more auctions.

 

As far as the power supply goes, get a new one, preferably a switching supply instead of a linear transformer-based one (small, lightweight PS vs wall-wart brick). You'll need 15v 1a center negative (which is opposite of most power supplies these days).



#11 ColorComputerStore OFFLINE  

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Posted Fri Oct 27, 2017 1:07 PM

I'm keen to build the PCB and get this to work on my new TS2068. Is the schematic and parts list available somewhere?

 

Thanks,



#12 factus10 OFFLINE  

factus10

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Posted Sun Oct 29, 2017 9:55 AM

You can find schematics and more over at the TS 2068 Yahoo Group, here:

https://groups.yahoo.../Twister board/



#13 ColorComputerStore OFFLINE  

ColorComputerStore

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Posted Mon Oct 30, 2017 7:43 AM

Wow, thanks for the head's up!






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