"Different" ZX81's

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

Post by Moggy » Sun Dec 04, 2016 11:35 pm

One of these days I might take a trip up to where the Timex factory was in Dundee, go into the local pub and shout...
"Any ex Timex workers from the Sinclair line here, the drinks are on me" :lol:
Last edited by Moggy on Wed Dec 07, 2016 4:48 pm, edited 1 time in total.

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1024MAK
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Re: "Different" ZX81's

Post by 1024MAK » Mon Dec 05, 2016 10:41 am

Somewhere along the line, the change from the issue 1 to the issue 3 is likely to have been driven by either cost, practically or need.

When you are talking about the numbers of zeddies that Sinclair were shifting, the cost of redesigning a PCB of that size is relatively small.

Mark

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Fwapp
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Re: "Different" ZX81's

Post by Fwapp » Mon Dec 05, 2016 10:46 am

My gut feeling its practicality/need, linked to the physical extras needed by the US market (all that bonding between case and PCB)
ZX80, ZX81 - 2C158C Bugged Rom iss.1, 2C158C "kludge fix" iss1, 2C184E iss1, 2C210E iss3, US NTSC iss1 "straight traces", US NTSC iss3 TS1000

balford
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Re: "Different" ZX81's

Post by balford » Tue Dec 06, 2016 1:58 pm

That would make perfect sense - the UK and USA Issue 1 PCB's were necessarily different, and I guess the Issue 3 was intended to be a 'universal' PCB with provision for extra components/shielding points required for the US market.

B

Moggy
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Re: "Different" ZX81's

Post by Moggy » Tue Dec 06, 2016 3:21 pm

balford wrote:That would make perfect sense - the UK and USA Issue 1 PCB's were necessarily different, and I guess the Issue 3 was intended to be a 'universal' PCB with provision for extra components/shielding points required for the US market.

B

If you look at the track layout of the USA board it's no more than a tidied up CAD version of the UK issue 1 albeit with a couple of extra components added ( the UK issue 1 has the transfer markings for the US components ) whereas the UK issue 3 is a total redesign hardly resembling the USA board at all in layout therefore not used state-side, so not universal I would have thought.

Judging by the lack of sockets I suggest the issue 3 was a cost cutting end of life for the UK-"Spectrum on the horizon"- measure rather than a universal board bearing in mind how quickly the Americans dropped the Timex 1000 after its intro in 1982 (discontinued 1983).

All supposition on my part I might add. :lol:

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Fwapp
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Re: "Different" ZX81's

Post by Fwapp » Tue Dec 06, 2016 3:53 pm

*Waits for B to drop his US Issue 3 PCB out" :lol:
ZX80, ZX81 - 2C158C Bugged Rom iss.1, 2C158C "kludge fix" iss1, 2C184E iss1, 2C210E iss3, US NTSC iss1 "straight traces", US NTSC iss3 TS1000

Moggy
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Re: "Different" ZX81's

Post by Moggy » Tue Dec 06, 2016 3:57 pm

Fwapp wrote:*Waits for B to drop his US Issue 3 PCB out" :lol:

No need we have a lovely piccy provided by your good self to look at! :lol:

Moggy
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Re: "Different" ZX81's

Post by Moggy » Tue Dec 06, 2016 4:01 pm

Also as the earthing/grounding call it what you will is little more than what looks like a couple of inductors and a tin strip touching the inside of a spray painted case, and was needed for radio emission suppression rather than earthing in the true sense of the word, I wouldn't have thought a universal design would be deemed unnecessary. :D

Again just me being a silly old tabby. :lol:
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Fwapp
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Re: "Different" ZX81's

Post by Fwapp » Tue Dec 06, 2016 4:25 pm

Now I'd call that an Issue 1(ish) based on the ULA/ROM/CPU layout. Hmmm, this is bugging me, I think your idea of taking a full wallet up to Dundee might be a good idea :D
ZX80, ZX81 - 2C158C Bugged Rom iss.1, 2C158C "kludge fix" iss1, 2C184E iss1, 2C210E iss3, US NTSC iss1 "straight traces", US NTSC iss3 TS1000

Moggy
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Re: "Different" ZX81's

Post by Moggy » Tue Dec 06, 2016 4:26 pm

Well buggar me with a fish fork! :shock:

It would seem that some UK issue threes did go state-side along with the tarted up issue 1.
Here's an American fitted board issue 3 with green masking dated 1981.

One more for Fwapp to collect. :lol:
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Last edited by Moggy on Tue Dec 06, 2016 4:32 pm, edited 1 time in total.

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