ZX81 Mod

Discussions about Sinclair ZX80 and ZX81 Hardware
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GCHarder
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ZX81 Mod

Post by GCHarder » Fri Mar 15, 2019 10:33 pm

There's a new youtube video of a guy showing the insides of a ZX81..

https://www.youtube.com/watch?v=Vv715KETc0w

It looks to be heavily modified, I was wondering what this mod might be.

Any guesses, looks like it has a substantial heat sink attached.

Regards;

Greg
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1024MAK
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Re: ZX81 Mod

Post by 1024MAK » Sat Mar 16, 2019 9:18 am

Not seen the video yet. But just going on the photo, the 74LS32 chip is four two input OR gates. It is mounted on what looks like some prototyping matrix board that either has a tinned ground plane on top or it is painted silver. It’s not a metal heatsink.

I would speculate that the OR gates in the 74LS32 may be being used for additional address decoding for either RAM, ROM or I/O.

Mark

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