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Old 21st Mar 2021, 12:28 pm   #192
ortek_service
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Default Re: I found it! A very sorry looking MK14.

Quote:
Originally Posted by SiriusHardware View Post
If you feel like re-drawing the circuit diagram of the issue II the way it really is with a modern circuit diagram package, I for one would find that useful. Maybe you could start with Slothie's issue VI and roll it back to issue II.

It would be interesting to know what proportion of the total output of MK14s were issue II, III, IV, V respectively. I don't count issues 0 or 1 as I have never seen one.

Issues II, IV and V each seem to have had respectable runs, issue III not so much.
A few people now have re-drawn the MK14 (although mainly latest versions) on a modern CAD system, to make it more readable. With people like Chris Oddy trying to keep it looking the same as the original, with all the same designators as well as overall style of the schematic - but sometimes with some extra labels to make it clearer.
So could probably edit one of these, to make older versions. However it does seem that it's not very clear how many version did actually exist originally / what version they actually were, if PCB (and schematic) wasn't labelled with this.
I've only found two versions of the schematic on the 'net so far, and later one is rather confusing in notes that say spare gates are only used on issue V, but they don't connect them, so possibly indicating it is only for previous issue 4.
The other main one is from the V1 manual, so might have presumed that was Issue 1.

Then there is the issue that there seems to be uncertainty on how many in total were actually made. This: https://en.wikipedia.org/wiki/MK14
gives either 15,000 or a rather high 50,000 (half that of the ZX80)
Although ZX80's seem to be about as rare (I've only got the PCB from one, that someone has sawn the keyboard part off!) , compared to the 1.5m made ZX81's which were commonplace - I've got quite a few, and still often see others for sale at rallies etc.)

What would be very useful, is a list of all the exact changes between the various issues of schematic / PCB - I've not seen a definitive list, so far.

Last edited by ortek_service; 21st Mar 2021 at 12:43 pm.
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