"Different" ZX81's

[msellan]

Thanks Moggy, that's good to know. I hadn't heard about the "back porch" issue until I started reading through these forums again. Not a day goes by on here without learning something new. I also still don't know enough about the different ULAs in circulation to know which ones have the issue and which ones don't (same goes for the bug issue in the ROM - how to find out that info?).

But alas, sadly, I only have an old B&W analog CRT television to use with all my ZXs. So it can only mean that my original Zeddy is just plain broke.

Best,

-mark

[Lardo Boffin]

You be careful though, Lardo, 6 months from now, you'll open a cupboard and wonder why you have so many ZX81's!

It does get addictive

Addictive? Nope! It's only two months later and I have 7! Oh wait...

[1024MAK]

Need to buy some more to catch up with me

<Although I appear to have more Zeddy PCBs than cases >

Mark

[Lardo Boffin]

Need to buy some more to catch up with me

<Although I appear to have more Zeddy PCBs than cases >

Mark

In my defence I have not been doing this long! But fully intend not to go crazy with this...

I have a 1:1 ratio of PCBs to cases and in fact 6 of them are even boxed! Although 2 of the boxes are far from brilliant...

[Lardo Boffin]

The last of my recent eBay madness arrived today (finally...) and is a very nice condition issue one, as below:-

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Check out the screen output! A bit dark but very well defined and solid as a rock! I wonder if this one would be usable with RF if a later ULA was put in?

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Lardo

[Moggy]

Niiiice.

Another clean example and four different chip manufacturers, so full house!

Judging by the picture Lardo I don't see why the later ULA wouldn't work seeing as the only thing lacking at the moment is brightness.

Now step away from ebay and give the rest of us a chance.

[Fwapp]

Nice Zeddy that one, Lardo - bet it's a 01 batch on the bottom of the 2C184E so one of the first of these types of ULA. A chap from NZ sent me a pic of a 8127 2C158E ULA, also on a cream PCB, helps define the transistion from 2C158E to 2C183E nicely.

[Fwapp]

In general for me it looks a bit like a chinese (or philippine) copy.
See the distance, line position and torsion of each single letter.
Looks crazy, nearly hand branded.

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Lots of ZX Spectrum ULA's with similar markings, Ferranti had a fab plant over there. Generally considered to be a bit less robust than the UK made ULA's which tended to carry the Ferranti logo. Basically - it's OK

[Lardo Boffin]

Well I bought another one... I saw the soft spongy feet and thought it looks interesting. It's a kludge fix (I assume) issue one! Nice. It works as far as I have tested it - most keys and it produces a dark output which is just about legible.

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The underside has what can best be described as 'frosting'. The board is a bit hazy except near the edge connector and solder points. It looks deliberate rather than age related?

Lardo

[Fwapp]

Wooo - nice!! The kludge fix ones are really nice to have in a collection. It amazes me that they could fix a software bug in the ROM by plonking hardware on the CPU - amazingly clever (at least from my point of view!)