ZX80 Slow mode mod

Discussions about Sinclair ZX80 and ZX81 Hardware
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retro_ready
Posts: 1
Joined: Sun Oct 01, 2017 3:22 pm

ZX80 Slow mode mod

Post by retro_ready » Sun Oct 01, 2017 4:05 pm

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.
Pete
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ZX80 Slow mode card Small.jpg
ZX80 Slow mode card Small.jpg (35.34 KiB) Viewed 217 times

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Andy Rea
Posts: 1267
Joined: Fri May 09, 2008 1:48 pm
Location: notts UK

Re: ZX80 Slow mode mod

Post by Andy Rea » Sun Oct 01, 2017 4:23 pm

My guess would be another 74LS93

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

Regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

Fruitcake
Posts: 90
Joined: Wed Sep 01, 2010 9:53 pm
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Re: ZX80 Slow mode mod

Post by Fruitcake » Tue Oct 10, 2017 10:09 pm

Andy Rea wrote:
Sun Oct 01, 2017 4:23 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 116 times
ZX80_SlowModeBoard_Schematic.jpg
ZX80_SlowModeBoard_Schematic.jpg (69.99 KiB) Viewed 116 times

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