"Different" ZX81's

Discussions about Sinclair ZX80 and ZX81 Hardware
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Fwapp
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Re: "Different" ZX81's

Post by Fwapp »

Moggy wrote:You like the Kayde board?
God no! It's a terrible bloody thing.

Cheap peel off transfers, the worst moulding ever made and in my case I have had to wrap tin foil around the ribbon cable as the repeat key electronics kick out some awful radio noise which sets me telly all of a quiver every time I press certain keys and the burping noise it sends through my sub-woofer is a joy to behold. :lol:


Love the full length space bar on the Dean by the way. :D

I consigned my Maplin K/B to the bin years ago, a shoddy piece of crap IMHO.

If you ever get the chance go for the Fuller K/B. Whilst the case is a bit shoddy and brittle it has the nicest/smoothest action of any K/B I've owned better even than Memotech plus both the RAM(depending on which one you get for this bit because the board fits a different way in some cases) and p/supply(on all cases) fit internally.
You don't like the Kayde then? :lol:

It's the aesthetic I like, but glad I know about the stickers now - I'll give it a miss.

One of the main reasons I went for the Dean was that the key legends live under a plastic cap which keeps them nice and tidy. It's also easier to replace them :)

I nearly got a fuller the other day on a FB group, but it was the version without the internal bus extension thingy? That'd be the version I'd like, I must admit. A mate of mine has one and love it :)
ZX80, ZX81 - 2C158C Bugged Rom iss.1, 2C158C "kludge fix" iss1, 2C184E iss1, 2C210E iss3, US NTSC iss1 "straight traces", US NTSC iss3 TS1000
Lardo Boffin
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Re: "Different" ZX81's

Post by Lardo Boffin »

Moggy wrote:
Who's joking? I have a big dog and I know where you live. :twisted: :twisted: :twisted:

At this point Moggy saddles up his big dog,Tyson,and heads south.
My reaction to this....
nervous.p
(927 Bytes) Downloaded 196 times
This took me way too long to do but isn't a bad likeness! :lol:
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
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1024MAK
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Re: "Different" ZX81's

Post by 1024MAK »

Yes, the Kayde keyboard is not the best of keyboards, but then, really good keyboards were expensive back then, and the keyboards for the ZX81 were a small market, so the companies were also small scale operations.

But, the Kayde keyboard is better than the ZX81 membrane and the Maplin keyboard (which would have been a lot better with a proper case and proper mounting support for the keyboard PCB).

Mark
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Moggy
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Re: "Different" ZX81's

Post by Moggy »

Lardo Boffin wrote:
Moggy wrote:
Who's joking? I have a big dog and I know where you live. :twisted: :twisted: :twisted:

At this point Moggy saddles up his big dog,Tyson,and heads south.
My reaction to this....

nervous.p

This took me way too long to do but isn't a bad likeness! :lol:
Brilliant that has really made my day nice one Lardo. :lol: :lol: :lol:
Moggy
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Re: "Different" ZX81's

Post by Moggy »

@Fwapp.

Please don't let my comments affect you in any way as from a collectors point of view ALL things zeddy are worthy of inclusion and I must admit the repeat key function is nice, glad you like the Fuller. :D

@Mark.

Ignore my ramblings Mark, you're right about the small scale thing. I often wonder how Memotech lasted as long as they did considering the high quality of their products for a niche market.

Speaking of membranes, having been critical of the original ones Rich was selling (top layer too thick) he persuaded me that the new ones are vastly improved so I bit the bullet and bought a couple and I have to say they are absolutely spot on. :D
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mrtinb
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Re: "Different" ZX81's

Post by mrtinb »

Lardo Boffin wrote:My reaction to this....

nervous.p

This took me way too long to do but isn't a bad likeness! :lol:
Great! :D
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
Lardo Boffin
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Re: "Different" ZX81's

Post by Lardo Boffin »

mrtinb wrote:
Lardo Boffin wrote:My reaction to this....

nervous.p

This took me way too long to do but isn't a bad likeness! :lol:
Great! :D
Hour and a half well spent then! I can see a whole load of zeemojis appearing...

Plus I now have a spreadsheet I can design screens with and just paste the values into TASM.

IMG_5548.JPG
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ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Lardo Boffin
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Re: "Different" ZX81's

Post by Lardo Boffin »

I recently started bidding on a zeddy because I wanted the paperwork it came with (so I had a complete zeddy, finally) but FWAPP kindly pointed out that with the spongy feet and ZX80 PSU it may be an early one with the ROM issue. I stuck with the bidding and lo and behold a very early zeddy which can't do maths! It's a funny world where I am excited about buying a technically 'broken' computer!

Inside:-
IMG_5582.JPG
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I didn't want to disconnect the keyboard as it currently works!
IMG_5583.JPG
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And finally PRINT SQR 0.25 gives me...
IMG_5579.JPG
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Happy days!
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Moggy
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Re: "Different" ZX81's

Post by Moggy »

Hi Lardo your collection is coming on in leaps and bounds. :D
Next step is to convert a spare one into a ZX80,now that is fun. :P

Nice little zeddy you have there with very early ULA. The bending of the top line to the left is normal for this wee beasty so no worries there.

The bugged ROM is a combination of numbers being stored inaccurately combined with a dodgy DIV routine so manifests itself in other ways than just SQR oddities. The SQR .25 is the one that's always wheeled out as an example hence the erroneous SQR bug moniker it attracted, but the bug goes slightly more deeper than that.
There are a couple of articles in ZX Computing by ZX maths guru Frank O'Hara which go into this in some depth.

https://archive.org/stream/ZX-computing ... 3/mode/2up

https://archive.org/stream/ZX-computing ... 7/mode/1up

https://archive.org/stream/ZX-computing ... 8/mode/1up



However for a temporary cure the next thing you need to collect is one of these.
Unfortunately whilst it gave a correct response for most SQR's and was satisfactory for most uses it didn't entirely eliminate the maths bugs in the ROM hence the later ROM issue.

Some info here....

http://www.binarydinosaurs.co.uk/museum ... /index.php
Attachments
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Fwapp
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Re: "Different" ZX81's

Post by Fwapp »

Oooh - 8109 date code ULA very nice!

Like Moggy says, the next step in your quest is to acquire a kludge fixed ZX81, with that rather clever little PCB on the Z80 :D

If you feel brave, could you pop the ULA out? I'm hoping it says 2C158E 03 on the bottom of it.

BTW, anyone else think the earlier keyboard membranes seem to be less fragile than later ones?
ZX80, ZX81 - 2C158C Bugged Rom iss.1, 2C158C "kludge fix" iss1, 2C184E iss1, 2C210E iss3, US NTSC iss1 "straight traces", US NTSC iss3 TS1000
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