"Different" ZX81's

[Moggy]

Which membranes? the ones That Rich currently sells or original factory fits?

In the case of the new ones the only fault I could find with the ones coming out of Poland was that the top layer was too thick/inflexible making keying in an uncomfortable nightmare.

The ones he sells now which I believe are made north of the boarder in Timex land are superb having the flexibility of the originals whilst being a good deal more robust ribbon wise.

As for original factory fits I am not aware of any difference in membranes used throughout the 81's production run and every one I once/now own(ed) early or late issue all looked the same even when peeled apart and failed through heat damaged cracked ribbons,which after a time I could no longer feasibly trim,rather than any intrinsic weakness in the membrane itself.

[Lardo Boffin]

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

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?

I just missed out on a kludge fixed one on eBay. Having just bought this one I'm out of cash for such things for a while. It went for around £45 I think.

I will pop out the ULA and let you know the number - providing it comes lose easily enough that is! Am sure it will.

I'm not really sure what to do with this one - ordinarily I would replace the keyboard and ZX8-CCB it to make it fully usable but this one is currently all original and working fine as is (maths aside). I guess I will make an exception to my rule (only buy stuff I will use) and just collect it. I seem to be doing that anyway looking at my signature! How did that happen?

Lardo

[Moggy]

!00% that is a 158 ULA trust me on this one!

With the RAM chip socketed it probably is kit zeddy rather than factory made so double bonus there Lardo.

[Fwapp]

I agree Moggy, its definitely a 2c158e - it's the batch number I'd like to confirm

[Moggy]

I agree Moggy, its definitely a 2c158e - it's the batch number I'd like to confirm

Hells bells Fwapp I forgot about that bugger, nice call.

[Lardo Boffin]

I'll make an effort to pop the chip tomorrow!

[Lardo Boffin]

One photo of the ULA:-

IMG_5605.JPG

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[Fwapp]

Thanks Lardo - you're a good'un

I've been trying to figure the numbers on the back of ZX81 ULA's - it's dead easy with 2c158e ULA's - convinced it's the batch number - so those made in 8102 were batch 1, 8106 batch 2 etc. It also points to datecodes that I've not seen

It all goes random after that

Pretty sure I have a 8125 somewhere, must dig it out.

Capture.JPG (38.84 KiB) Viewed 4439 times

[Moggy]

Nice list there Fwapp, is this an official list or your own endeavours?

I have just had a look at my last remaining 158 and it Tally's with your list; 8113 #5
It also has the number 26 embossed onto it though could just be a package stamp.

Just checked a couple of 184's

topside 8236 underside STI 2C184E PHIL 3480 embossed18

topside 8130 underside 2C184E 2902 embossed39

[Fwapp]

It's a list I've put together - I'm a little bit sad in that I like to understand timelines and the like

Thanks for your numbers, I'll pop it in the list as well.