ZX80 Slow mode mod

Discussions about Sinclair ZX80 and ZX81 Hardware
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retro_ready
Posts: 1
Joined: Sun Oct 01, 2017 4:22 pm

ZX80 Slow mode mod

Post by retro_ready »

Hello everyone.
I am new to this forum and this is my first post, I have owned and still got a ZX80 since it was introduced back in the 80s, I upgraded the Rom to ZX81 and installed an interface card to give slow mode, then it lay in a box for the next 30 or so years, I have recently converted it my ZX80 back to original by removing all mods, the question I have is related to the slow mode interface, I want to keep the interface card but it’s not complete having lost an IC, I was wondering if anyone has any info on this card as any info I had has long since disappeared, it would be nice to restore the card as a part of ZX80 history.
Any info would be much appreciated.
Last edited by retro_ready on Thu Dec 05, 2019 10:12 pm, edited 1 time in total.
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Andy Rea
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Re: ZX80 Slow mode mod

Post by Andy Rea »

My guess would be another 74LS93

It is only a guess. To be sure some reverse engineering could help.

Regards Andy
what's that Smell.... smells like fresh flux and solder fumes...
Fruitcake
Posts: 346
Joined: Wed Sep 01, 2010 10:53 pm

Re: ZX80 Slow mode mod

Post by Fruitcake »

Andy Rea wrote: Sun Oct 01, 2017 5:23 pm My guess would be another 74LS93
Yes it's a 74LS93! :D
ZX80_SlowModeBoard_Photo.jpg
ZX80_SlowModeBoard_Photo.jpg (91.13 KiB) Viewed 2257 times
ZX80_SlowModeBoard_Schematic.jpg
ZX80_SlowModeBoard_Schematic.jpg (69.99 KiB) Viewed 2257 times
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