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Science of Cambridge (Sinclair) MK14

And yet another one up for sale on a certain auction site.

This one may go for even more money by the look of the bidding frenzy that has already started...

Dave
 
daver2 said:
And yet another one up for sale on a certain auction site.

Dave
Click to expand...

Of the three images showing the unit, the first appears to picture it as a museum exhibit. The second and third images appear to be the same machine (solder blobs on rear connector, distinctive yellow capacitor) - I find it a little bit sad that a museum would be selling something like this instead of keeping it.

A reasonably nice looking issue IV, it has the 'improved' 'plastic dimple button' version of the keypad presumably with calculator style metal dome contacts rather than the earlier conductive rubber mat underneath the key legend sheet - also that version of the PCB is already laid out for the optional fitting of keypad switches identical to the one already used for the reset switch, although it would be a pity to remove the original keypad components when they have stayed with the machine for so long and so many other examples have lost theirs.

Improved monitor and extra RAM are already fitted but the optional 8154 I/O RAM IC is not present - not sure how easy it is to get hold of those now?

Doesn't seem to have a manual or any of the other options (cassette interface, VDU, PROM programmer).

The third image in the listing is interesting as it clearly shows that the rear edge connector has contact fingers on the print / track side of the issue IV PCB, but also clearly shows that they don't go anywhere! To use them for, e.g., connection of the VDU, the user has to wire those to the relevant address / data / control lines himself / herself.

Translated crudely to English (thanks Google) the description text states that it was kept in controlled conditions behind glass for many years, that the display lights up (as we can see from the images) but that the keypad only responds sporadically to key presses 'possibly due to the condition of the keypad components', and that in any case it is deliberately listed as 'not working' due to its vintage and offered (understandably) with no guarantees.
 
It seems to have 'half' of its expansion RAM. The socket behind the crystal is empty.

The PCB assembly has been 'butchered' a bit too much for my liking...

I tried to get hold of some 8154's a while ago - but no luck. I may have another go again. I have a 'guy' who can find obsolete chips for me (there is a minimum order though).

Dave
 
>It seems to have 'half' of its expansion RAM...

Good spot, I hadn't noticed that. 2111 RAMs are probably still not too difficult to find.

About 10 years ago I broke up an old standalone eprom programmer, which turned out to have not only an SC/MP but an 8154 in it - they now form part of the small 'critical spares' stock for my own MK14. The toroidal power transformer from that old programmer unit is also what powers the MK14 these days.

I don't think the PCB condition is too bad on that machine - certainly mine is worse, due to the fact that it had track cuts and other alterations made to support upgrades such as the add-on single-step circuitry (a few gates) and the VDU, which was fitted for a while.

On the auction-site machine, that wire running across the back along the edge connector is probably to tie Sense-A low, a necessary mod when the new monitor is fitted but the single-step hardware is not. It could have been (and still could be) done much more discreetly on the underside of the PCB with a short link directly from the Sense-A pin pad on the CPU to the nearest 0V point.

Aside from that, I can't see much in the way of track damage or tracks cut / repaired.
 
daver2 said:
Only GBP 446 this time - they are getting cheaper :)!

Dave
Click to expand...

I actually thought it would go for more as the problems with the keypad were at least honestly described and wouldn't be difficult to fix. Nor would the missing RAM IC be much of a problem to find.

The question is, who is it that is paying so much for these things?

I'm guessing people who had them originally and for whom they were the very first step to a successful and reasonably well paid career in IT or software development. For people in that position, a few hundred pounds / nearly a thousand pounds to relive a little bit of their past isn't going to break the bank. I just hope they aren't too disappointed when the reality of what it is they've paid so much for hits them.

Moreover, there will come a point in the not too distant future when all of that generation (including me) will start to fall by the wayside, until there will be no-one left who has any memory of what an MK14 is - and at that point, they will be nearly worthless again. As you've suggested earlier, values may already have hit a plateau and we could be seeing the beginning of a long decline in MK14 prices. Any example bought at today's inflated prices stands a real chance of depreciating, rather than increasing in value.
 
Yet another! Like buses - none for ages and then several at once. This one at least is comprehensively described, warts and all.

http://www.ebay.co.uk/itm/Sinclair-...working-/331856841531?&_trksid=p2056016.l4276

Pros:
-Improved 'new' monitor is fitted (shown by '0' prompt rather than '-' prompt).
-Late version (issue V) PCB, already laid out for optional key switches
-Metal dome switches of a later original version of the keypad are present
-Difficult-to-obtain optional 8154 I/O RAM chip is present
-Overall subsystem is working, can step through / display addresses and data

Cons:
-Optional extra RAM is not present
-PCB tracks in the vicinity of the display are in extremely bad condition
-Probable faults on the actual display (see below)
-Keypad legend overlay has been lost - could possibly print / laminate a replacement

Other:
-Crystal has been changed from original 4.43Mhz to 4.00Mhz - possibly used with an MK14 VDU, which required this change.

I suspect a fault on the actual display because normally a fault on the display connections will take out either a whole display cell or the same segment across all eight display cells. In this case - where six of the cells should be showing '0', we've got a lower left segment on one cell missing, and an upper right segment on another cell missing - generally this is going to be a problem with the actual display segments in question.
 
July 2016 - The Centre For Computing History (UK) has posted a nice Youtube interview with Ian Williamson, who built the prototype MK14. It's quite long ( one hour eleven minutes) and the first hour dealing with his background, upbringing and education, will probably be easier for British viewers to relate to.

At one hour in, the interview moves to the subject of the MK14 itself and there's a nice bonus in the form of the prototype MK14 itself, which Mr Williamson has apparently donated to the centre. It's also shown side by side with a particularly clean early issue MK14. The production MK14 did not exactly follow Williamson's design in the end because, when approached to make it, National Semiconductor offered to supply equivalent kits for SOC using entirely Nat Semi parts, and it was their version which was released as the production version of the MK14.

https://www.youtube.com/watch?v=awlqzippsSc
 
End July 2016 - yet another MK14 up for sale. Where are they all coming from?

http://www.ebay.co.uk/itm/Science-o...573926?hash=item21137854e6:g:X9QAAOSwRgJXkAIt

Appears completely populated, although it has its display mounted offboard along with a homebrew moving-switch keypad. It's a late version (issue V) so it has the calculator-style metal-dimple switches rather than the original (awful) rubber mat contacts, and the PCB is laid out for the insertion of optional key switches (same type of switches as the reset switch).
 
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Another well hidden Science of Cambridge MK14 Youtube video here, this one seemingly from 2011 - difficult to find as it's not well named or tagged. It's shown running the 'Message' program from the user manual with the original quintessentially British text:- "AS YOU CAN SEE S-OF-C IS A JOLLY FINE BUY". I always wondered why 'SCIENCE' wasn't spelled out in full since it was doable on 7-segment displays, but 'CAMBRIDGE' with the 'M' was always going to be awkward.

https://www.youtube.com/watch?v=BtgUA7O8pkc

The market for MK14s has been quite lively lately (2016), but nobody seems interested in showing them off. It would be nice to see some new videos of working MK14s.
 
The first new MK14 related video for a while, this one a decent little little talk about the machine from Computerphile...

Featuring not only a very clean example of the MK14, but an even rarer unbuilt kit as well. If only they would (or could) scan the PCB and put the scans in the public domain, I know there are a lot of people who would like to build one... ...again.

https://www.youtube.com/watch?v=O_vhWxu-spA

It would still be nice to see some more videos of working MK14s, so if you have one, don't be shy.
 
Curious.. how rare are MK14s? I saw an auction for one a year or two ago that went to 1000 pounds.
 
They are fairly rare - but they do come up for sale occasionally. They then can go for 'silly' money!

Round about £500-£600 is they typical value they sell for.

Dave
 
The most common estimate of numbers for MK14s is that about 50,000 were sold, all as kits (they were aimed at electronics hobbyists).

I used to think it depended on condition, but there seems to be neither rhyme nor reason as to what people will sometimes pay for them. At the time of writing (November 2017) it is still relatively rare for them to go for a four figure sum - those which do are in very good condition and have at least the manual and usually some auxiliary accessories as well, such as the optional cassette interface or optional VDU unit.

At the other end of the scale, even those with parts missing, not working or just in plain very bad condition still go for hundreds of UK pounds which is out of all proportion to what you would be getting for that money - basically a primitive hex-input microprocessor development system with (officially) at most 600+ bytes of RAM. Their value seems to be based only on their being Sinclair's first 'computer' and on their nostalgic pull on those who did originally have one but let it go / threw it out and now want to reclaim a little bit of their past.

Falter, if you feel like looking for one yourself the main thing is to find one which still has its original keypad in working order, relatively speaking. The early version 'rubber membrane' keypad was so poor that it was often (as on my own MK14) replaced with something better fairly quickly, so MK14s with original keypads are even rarer than MK14s overall.

The other thing is to ensure that the PCB tracks, especially around the 7-segment display, are in good condition. It was very common for people to build them originally as they were shown in Computerphile's video and then, not long after, to remove the display and extend its wiring so that the machine could be put into some kind of enclosure. Desoldering tools being what they were back in the day, the removal of the display wasn't always done neatly or well and some of the ones which came up for sale recently were good (...bad?) examples.
 
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Nice article. I don't think there is a more detailed article about the MK14 VDU anywhere else on the 'net'.

You mention in the article that you have reproduced the issue 2 VDU, and you have never seen another original VDU to compare it with.

I have just looked at mine and mine is also ... issue 2, so unfortunately I can not inform you of the difference between issue 2 and issue 1 VDUs.

I have only ever seen one MK14 VDU PCB sold on ebay, it was included with an exceptionally nice original MK14 and I think the VDU was actually unbuilt.
 
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